concept map circulatory system critical thinking

ORIGINAL RESEARCH article

Developing seventh grade students’ systems thinking skills in the context of the human circulatory system.

• Department of Science Teaching, Weizmann Institute of Science, Rehovot, Israel

Developing systems thinking skills in school can provide useful tools to deal with a vast amount of medical and health information that may help learners in decision making in their future lives as citizen. Thus, there is a need to develop effective tools that will allow learners to analyze biological systems and organize their knowledge. Here, we examine junior high school students’ systems thinking skills in the context of the human circulatory system. A model was formulated for developing teaching and learning materials and for characterizing students’ systems thinking skills. Specifically, we asked whether seventh grade students, who studied about the human circulatory system, acquired systems thinking skills, and what are the characteristics of those skills? Concept maps were used to characterize students’ systems thinking components and examine possible changes in the students’ knowledge structure. These maps were composed by the students before and following the learning process. The study findings indicate a significant improvement in the students’ ability to recognize the system components and the processes that occur within the system, as well as the relationships between different levels of organization of the system, following the learning process. Thus, following learning students were able to organize the systems’ components and its processes within a framework of relationships, namely the students’ systems thinking skills were improved in the course of learning using the teaching and learning materials.

Introduction

Science plays a key role in our culture. As such, the range of issues dealing with decision making, both individually and globally is rising. One of the areas in which we are required to make decisions on a daily basis is medicine and health. As the information is readily available to all, the main difficulty lies in the ability to properly understand and integrate the information. Developing systems thinking skills in school may provide useful tools to deal with the vast amount of information and thus can help learners in developing their decision making skills. Moreover, adopting the approach that views the human body as one complex system that divides into multiple levels of organization and has many components, which interact with each other, may promote a deeper understanding of biological processes. That approach is essential for developing wise decision making skills regarding health issues. In the era of “Science for All,” developing these skills in junior high school is more important than ever before.

A systems perception enables an analysis of the learned phenomena from a meta-cognitive perspective emphasizing the entirety, the sum of its components, and the connections and interactions between them ( 1 – 3 ). We describe below the theoretical basis of our study, and specifically what is systems thinking, how does systems thinking skills develop, and what are the difficulties students of various grade levels encounter when learning about various systems in general and about the human circulatory system in particular.

What is Systems Thinking?

The current literature on systems thinking provides various definitions to the term system. From basic definitions, such as “The basic conceptualization of a systems is relatively simple; a system is a collection of parts and/or processes” ( 4 ) to broad definitions emphasizing the significance of the interactions between the system components, such as “A system is an entity that maintains its existence and functions as a whole through the interaction of its parts. However, this group of interacting, interrelated or interdependent parts that form a complex and unified whole must have a specific purpose, and in order for the system to optimally carry out its purpose all parts must be present. Thus, the system attempts to maintain its stability through feedback” ( 3 ). The characteristics of the system whole are often un-identical to the individual system components ( 3 , 5 , 6 ). Therefore, in order to profoundly understand a complex system, an understanding of its individual components is insufficient but rather the net of interactions between all the system components should be addressed. Analysis and understanding of a given system require developing higher order thinking skills and high cognitive abilities.

The recent Framework for K-12 Science Education, published by the United States National Research Council ( 7 ), emphasizes the necessity of developing systems thinking skills among students of different age levels. The framework anchored an objective of design principles and standards for science education to suit the twenty-first century education system while reducing curriculum content and suggesting curriculum reorganization based on a reduced number of concepts. The framework outlines three dimensions: scientific and engineering practices, crosscutting concepts, and core ideas for all content fields. “Systems and system models” is listed as one of the crosscutting concepts in this framework. The recommendation is to expose the students to the systems thinking approach starting from the primary grades. The significance of a system definition for means of research and learning is emphasized in this framework based on the fact that “the natural and designed world is complex; it is too large and complicated to investigate and comprehend all at once. Scientists and students learn to define small portions for the convenience of investigation. The units of investigations can be referred to as ‘systems’… A system is an organized group of related objects or components that form a whole… Although any real system smaller than the entire universe interacts with and is dependent on other (external) systems, it is often useful to conceptually isolate a single system for study. To do this, scientists and engineers imagine an artificial boundary between the system in question and everything else” ( 7 ).

How Does Systems Thinking Skills Develop?

Three models for systems thinking were suggested in the literature ( 2 , 3 , 8 ). Each model clarifies and illuminates a different aspect of developing systems thinking skills among students.

Systems thinking hierarchical model

A cognitive model presenting eight hierarchical stages of the development of systems thinking skills ( 3 ). According to this model, the cognitive skills developed at each stage constitute a basis for developing higher systems thinking skills. The model has been modified and in the study by Ben-Zvi Assaraf et al. ( 9 ) the development of a systems thinking skills was described as follows: (1) identifying the components and processes of a system, (2) identifying simple relationships among a system’s components, (3) identifying dynamic relationships within a system, (4) organizing the system’s components, their processes, and their interactions, within a framework of relationships, (5) identifying matter and energy cycles within a system, (6) recognizing the hidden dimensions of a system (i.e., understanding phenomena through patterns and interrelationships not readily seen), (7) making generalizations about a system, and (8) thinking temporally (i.e., employing retrospection and prediction).

Studies that used this model for examining student systems thinking skills gathered the eight stages into three sequential hierarchical levels: system component analysis (stage 1), synthesis (stages 2–5), and implementation [stages 6–8 ( 9 , 10 )]. These studies presented a typical pyramid structure, the wide base of the pyramid representing students possessing analytical skills, and the narrow vertex of the pyramid representing students possessing implementation skills. Going up the pyramid, the systems thinking level increases and the number of students possessing systems thinking skills decreases. A student that had reached the highest thinking level (implementation) had to have successfully completed the prior stages [analysis and synthesis ( 9 , 10 )].

Systems thinking competence for cell biology education

According to this model, systems thinking competence for cell biology education is anchored in four elements: (1) being able to distinguish between the different levels of organization, and to match biological concepts with specific levels of biological organization; (2) being able to interrelate concepts at the cellular level of organization (horizontal coherence); (3) being able to link cell biology concepts to concepts at higher levels of organization (vertical coherence). An additional element refers to the relationship between systems thinking skills and an understanding of models of the living cell: (4) being able to think back and forth between cell representations ranging from abstract cell models to real cells seen under a microscope. Students have difficulties in differentiating structures and processes at different levels of organization as well as in making connections between structures and functions at different levels of organization, while attempting to provide explanations for biological phenomena. Among others, these difficulties derive from a lack in forming significant relationships between the various organizational levels during the teaching and learning process ( 1 , 2 , 11 , 12 ).

Structure-behavior-function model

At the foundation of this model is the assumption that the organization of knowledge during the learning process may affect the manner in which the learners organize their knowledge regarding a given system ( 8 ). This model was developed in the field of engineering and it offers a conceptual representation, which focuses on a causative connection between three system aspects: (1) structure: the system components and the relationships between them, (2) behavior: the dynamic interactions between the system components and existing mechanisms in the system, and (3) function: the essence of the system and its components. For experts, the function and behavior in a system constitute a principle knowledge organizer and a foundation for understanding the system, whereas for beginners the system structure constitutes the principle knowledge ( 13 ). In addition, findings show that the use of conceptual representation with an emphasis on a function centered conceptual representation in teaching has numerous significant advantages in comparison with the use of a structure centered conceptual representation. The advantages are in enabling to respond to essential questions regarding the system role, as the broad questions are divided into more specific sub-questions. This type of questions encourages thinking and argument building. Searching for answers to a question encourages meaningful learning. Another advantage is in creating a cognitive challenge for the learners. In the attempt to answer questions regarding the system role, the students are required to gather their prior knowledge and examine the new knowledge acquired in light of their prior knowledge. In addition, it may promote the creation of meaningful connections between the system components at different levels of organization. Thus, organizing the teaching through conceptual representation may facilitate the students and assist their profound understanding of complex systems ( 8 ).

Using those three models, we constructed a unified model, which enabled us to both develop learning materials as well as to characterize systems thinking skills in biology (Table 1 ).

Table 1 . A unified model for characterizing systems thinking skills in biology .

The unified model (Table 1 ) emphasize the following three principles, which served as the foundation for our study: (1) the development of systems thinking skills consists of several sequential stages arranged in a hierarchical manner, (2) the conceptual representation of a given system influences the way students perceive it, (3) one cannot understand processes in a biologic system without an understanding of processes and components at different levels of organization.

Difficulties in Comprehending Systems

Current research on the development of systems thinking argues that students of different age levels, from pre-school to college, face difficulties in understanding various concepts related to systems thinking, such as the respiratory system in biology ( 1 ), the water cycle ( 3 ), and the rock cycle in Earth Sciences ( 14 ). These difficulties are expressed through a superficial understanding of the system, fragmented, and non-coherent knowledge of the biological phenomena as well as misconceptions ( 12 , 13 , 15 ). Those students’ difficulties might be a result of the complexity characterizing natural systems, which include multiple components at different organizational levels within which dynamic interactions take place ( 13 ). Thus, emphasizing that the components composing the system are insufficiently addressed as well as the processes that take place in the system ( 9 ). In addition, in an analysis of Biology text books, findings showed that many books do not attempt to form significant connections between the different organizational levels of biological systems. In this way, for instance, the discussion of the cell concept is often separated from the discussion of the human body systems ( 2 ). This raises the necessity for developing effective tools for systems analysis and knowledge organization in the teaching and learning of biological systems. Other research studies in this area address the characterization of systems thinking ( 3 , 10 ), designing, and examining teaching and learning materials for developing systems thinking skills ( 3 , 8 , 12 ).

The development of cardiovascular health knowledge requires the ability to analyze and understand the heart and blood systems. Due to the complexity of natural systems, students, of all ages, experience great difficulty in understanding and analyzing these systems ( 3 ). For example, Hmelo et al. ( 1 ) described sixth grade students’ difficulties in understanding the human respiratory system. They found that those difficulties derive from a lacking understanding of the existing processes at different organizational levels. They noted that a profound understanding of the functioning systems in the human body entails both an understanding of the existing processes at different organizational levels as well as an understanding of the systems function as a whole. Similarly, Arnaudin and Mintzes ( 16 ) examined misconceptions about the human circulatory system among students at the elementary, secondary, and college levels. Their results indicate that the most resilient to change are understandings of the various organizational levels of the circulatory system and the connections between its components and the processes that take place in the system. A standardized test of cardiovascular health knowledge that was administered to 12–18 years old students and to 20–60 years old adults showed that young students can correctly answer less than half of the items ( 17 ). Although this test showed that health knowledge increases gradually during the junior high and high school years, the authors pointed out the importance of developing cardiovascular health knowledge at a young age. We therefore focused our study on the first year of junior high school, and specifically on the seventh grade.

In this study, we characterize students’ systems thinking skills in the context of a teaching and learning unit about the human circulatory system, which was developed based on the unified systems thinking model described above (Table 1 ) and considering students’ difficulties in comprehending systems. Specifically, we asked whether seventh grade students, who studied about the human circulatory system, acquired systems thinking skills and what are the characteristics of those skills?

Materials and Methods

The context of the study.

Teaching and learning materials focusing on the human circulatory system were developed using the unified model described above (Table 1 ). Specifically, a unit of 30 teaching hours, which addresses the human circulatory system was developed for seventh grade students ( 18 ). The unit was developed in accordance with the requirements from seventh grade students in the new Israeli Ministry of Education Science and Technology curriculum for junior high schools ( 19 ). Within this unit, 12 learning activities, organized in a hierarchical order based on the stages in developing systems thinking were integrated. A description of these learning activities appears in Table 2 .

Table 2 . Description of learning activities in the teaching and learning materials .

The design of the unit utilized teaching strategies that encourage the learners to construct knowledge while creating learning opportunities in which the learner is active in the organization of his or her own knowledge. This approach is based on the belief that active personal knowledge construction, or knowledge integration, contributes to a meaningful learning process ( 20 ). Thus, activities associated with knowledge summarization and organization, constitute a significant portion of the teaching and learning materials. Figure 1 shows a knowledge summarization and organization diagram integrated in the teaching and learning materials, along with the model for developing systems thinking skills.

Figure 1. Knowledge summarization and organization diagram from the teaching and learning unit ( 18 ) .

The diagram shown in Figure 1 was designed to promote knowledge organization and analysis of a given system, while specifically differentiating between components, processes, and the relationships between them. The students are initially asked to create a list of the existing components and processes in the system, at different levels of organization. Subsequently, they are asked to connect between the “components” and the “processes.”

Research Population

The research population consisted of seventh grade students ( n = 75, 12–13 years old), from three different junior high schools in Israel, and a similar number of boys and girls. The total number of students who participated in the study was higher (approximately 90 students), but as a few students were absent from the first lesson and a few were absent from the last lesson, only the concept maps that were formed by students who were present in both time points were taken for analysis.

Concept Maps

In order to characterize student systems thinking skills, concept maps were used. A concept map includes: concepts and relationships. Usually, the concepts appear in circles or rectangles and the relationships between them are indicated by lines and by sentences that are formed between concepts and represent the relationships between the concepts. The relationships describe the bond between each concept pair in one word or sentence ( 21 ). In the current study, students were instructed by the researcher to construct concept maps. Initially, they practiced the construction of concept maps using concepts of close interest (for example, family relationships or familiar television programs). This deriving from the assumption that practicing the construction of concept maps is essential for the concept map to serve as a research tool ( 22 ). In the next stage, the students were asked to create a concept map of the human circulatory system. The students received a blank page with 12 empty circles, along with instructions for creating a concept map. The instructions did not include any concept and did not address the hierarchy between the concepts, therefore the students were free to elicit any concept they like and to create a personal framework of concepts and relationships matching their perceptions. The process resulted in concept maps with concepts and relationships that were freely elicited by the students and describe the way in which the students organized their knowledge about the human circulatory system.

Analyzing the concept maps ( n = 150) created by the students enables examining the mental representation of the students. Comparing the concepts elicited by the students as well as the concept maps they created before ( n = 75) and following ( n = 75) the learning process enabled us to probe the possible conceptual change the students endured in the course of learning. The analysis of the concept maps was carried out using the unified model for characterizing systems thinking in biology education, as detailed in Table 3 .

Table 3 . Analysis of the concept maps using the unified model for characterizing systems thinking in biology education .

The analysis started from the left column in Table 3 , which is hierarchically organized from top to bottom, and continued by moving from left to right in each of the rows in the Table. The second column describes the data analysis of the concept maps. Ten percent of all concept maps were independently analyzed by two researchers and discussed until 95% agreement was achieved. In each row, the basic level is detailed in the third column and the high level in the fourth column, for each of the stages in developing systems thinking skills (Table 3 ). In addition, for measuring students’ ability to organize the system components in a framework of interactions, students’ concept maps were analyzed in light of four typical concept maps models A–D [see Figure 2 , following ( 23 )]. The four models describe the complexity level of the interaction framework presented in each map. Model A represents the simplest model (“pairs” model, single, pairs or trios of concepts), model B represents a more complex model (a “spoke” model, one central concept linked to other concepts), model C represents a complex model relative to B (a “chain” model, a few concepts linked to each other), and model D represents the most complex model (a “net” model, a branched framework of concepts).

Figure 2. Four typical models (A–D) of students’ concept maps [following Ref. ( 23 )] .

Independent samples t -test, Paired t -test, as well as χ 2 test were used for measuring the significance of the observed differences between the two groups (before and following the learning process).

Student systems thinking skills were examined in light of the unified systems thinking model presented above. The results are organized according to the four primary systems thinking development stages that are listed in the left column of Table 1 : (1) the ability to identify components in the system, (2) the ability to identify simple relationships between the system components, (3) the ability to identify dynamic relationships between the system components, (4) the ability to organize the system components in a framework of interactions. The analysis of the students’ concept maps ( n = 150) shows that for each of the following parameters a significant increase was noted when comparing between concept maps constructed by the students before ( n = 75) and following ( n = 75) the learning process: number of concepts, number of relations between concepts, number of structural relations between concepts (simple relationships between the system components), number of process relations between concepts (dynamic relationships between the system components), and number of “junctions.” The term “junction” refers to a concept that has relations to at least three other concepts on the map, demonstrating students’ ability to organize the system components in a framework of interactions (Figure 3 ), thus implying an improvement in students’ acquisition of systems thinking skills, following the learning process.

Figure 3. Concepts and relations appearing in students’ concept maps, before and following the learning process . Significant differences are indicated by asterisks [* p < 0.05, ** p < 0.01, *** p < 0.001). Independent samples t -test.

The Ability to Identify the Components of a System

The concepts students chose for building their concept maps were examined in light of their organizational level. The concepts were classified into three organizational levels: (1) macro level (organism, system, organ, tissue), (2) micro level (cells, organelles), and (3) sub-micro level [molecules, atoms; following Ref. ( 24 )]. A comparison between the concepts chosen by the students before and following the learning process indicates a significant increase in the average number of concepts in each of the organizational levels, by the end of the learning process (see Figure 4 ). The highest increase was observed in the number of concepts at the macro level and the lowest in the number of concepts at the micro and the sub-micro levels.

Figure 4. Distribution of concepts addressing system components according to their organizational levels before and following the learning process . Significant differences are indicated by asterisks [* p < 0.05, ** p < 0.01, *** p < 0.001]. Paired t -test.

Examining the concepts themselves revealed that the concepts with the highest incidence in the students’ concept maps before the learning process (concepts appearing in 50% of the student entirety word lists) are: heart (100% of the students mentioned this concept), blood (79% of the students mentioned this concept), artery (56% of the students), vein (57% of the students), and red blood cell (53%). However, the highest incidence concepts in students’ concept maps following the learning process (concepts appearing in more than 50% of the student entire concept lists) are: heart (100% of the students mentioned this concept), vein (90% of the students mentioned this concept), artery (89% of the students), capillary (78% of the students), blood (71% of the students), oxygen (68% of the students), red blood cell (67% of the students), blood cells (57% of the students), and lungs (53% of the students). It is interesting to note that the concept capillary, mentioned by 78% of the students at the end of the learning process, was mentioned only among 23% of the students before the learning process. The concept oxygen, mentioned by 68% of the students at the end of the learning process, was mentioned only by 24% of the students before the learning process, whereas the concept lungs, mentioned by 54% of the students at the end of the learning process, was mentioned only among 17% of the students before the learning process. Identifying these components as significant in the human circulatory system, by a high percentage of students, may indicate a connection the students form between the human circulatory system and the respiratory system. This connection is not trivial and it may imply an understanding of the system as a whole.

The Ability to Identify Simple and Dynamic Relationships among a System’s Components

As mentioned above, following the learning process the students formed more relations between the concepts (Figure 3 ). The increase in the number of relations is expressed both among the structural relations (or simple relationships, Table 1 ) as well as among the process relations (or dynamic relationships, Table 1 ). Interestingly, differences were similarly detected in both the simple as well as in the dynamic relationships, and the process relations were even more pronounced in the concept maps than the structural relations (Figure 3 ), even though the ability to identify dynamic relationships was previously reported to be more difficult for learners ( 3 ).

The relationships students formed between concepts were further classified according to the various organizational levels into four groups: (1) sub-micro – micro (relationships connecting between concepts at the sub-micro level to concepts at the micro level of organization), (2) micro–macro (relationships connecting between concepts at the micro level to concepts at the macro level of organization), (3) sub-micro–macro (relationships connecting concepts at the sub-micro level to concepts at the macro level of organization), (4) the same level of organization (relationships connecting between concepts at the same level of organization). Interestingly, despite a significant increase in the number of relationships at each organizational level (both in the simple relationships as well as in the dynamic relationships, Figures 5 and 6 ), the most significant difference was identified in the relationships between concepts at the same organizational level, mostly between concepts at the macro level (Figures 5 and 6 ). This finding is in line with previous studies which showed that students tend to connect components at the same level of organization and face difficulties in identifying relationships between the various levels of organization ( 12 ).

Figure 5. Distribution of simple relationships among students’ concept maps before and following the learning process according to the level of organization . Significant differences are indicated by asterisks (* p < 0.05, ** p < 0.01, *** p < 0.001). Paired t -test.

Figure 6. Distribution of dynamic relationships among students’ concept maps before and following the learning process according to the level of organization . Significant differences are indicated by asterisks (* p < 0.05, ** p < 0.01, *** p < 0.001). Paired t -test.

Examining the relationships between the different levels of organization raises an interesting conclusion; the observed improvement in students’ ability to identify relationships between the different levels of organization is more significantly pronounced in dynamic relationships than in simple relationships. It may be assumed that identifying dynamic relationships encourages the formation of associations between various levels of organization and thus, a more profound understanding of the system.

The Ability to Organize the System Components within a Framework of Interactions

Interaction framework analysis was carried out using the four models distribution (A–D, see Figure 2 ) among the entirety of students’ concept maps, composed before and following the learning process. An increase in the complexity of the concept maps was observed following the learning process (see Figure 7 ). The structure of 52% of students’ concept maps show higher complexity following the learning process (see Dark gray in Figure 7 ), while the structure of 44% of students’ concept maps show no change following the learning process (see Medium gray in Figure 7 ), and a smaller percentage (3.9%) of students’ concept maps show lower complexity following the learning process (see Light gray in Figure 7 ). It is interesting to note that in the majority of these maps, the total number of concepts and relationships increased. An analysis of the concept map models indicates that the most dominant students’ concept map model before the learning process was model B (“spoke,” 43%), whereas the most dominant model following the learning process was model D (“net,” 39%). Thus, indicating that a more branched knowledge structure and therefore, a probably more profound understanding of the system can be identified following learning. Likewise, model A, representing single, pairs or trios of concepts, appears among 25% of the students’ concept maps before the learning process and in only 8% of the students’ concept maps following the learning process.

Figure 7. The percentage of students’ concept maps classified to models A–D before and following the learning process . The percentages indicate the relative number of each of the models among the students’ concept maps in each time point ( n = 75). χ 2 test. The three shades of gray in the figure represent: (i) the percentage of students’ concept maps, which show an improvement in their structure following learning (Dark gray); (ii) the percentage of students’ concept maps, which show no improvement in their structure following learning (Medium gray); and (iii) the percentage of students’ concept maps, which show a regression in their structure following learning (Light gray).

Another interesting point to note is that 28% of the students’ concept maps showed an improvement of “one step” (namely, advanced from model A to model B, or from model B to model C) following the learning process, while 19% of the students’ concept maps showed an improvement of “two steps” (namely, advanced from model A to model C or from model B to model D), and 5% of the students’ concept maps showed an improvement of “three steps” (namely, advanced from A to D). Thus, many students enriched their knowledge constructs in terms of the number of concepts and the relationships between them. A difficulty in advancing from one model to a more advanced model was observed among the students, since only a very small percentage of students formed more complex concept maps following learning.

In this study, we aimed to examine whether seventh grade students acquired systems thinking skills as well as the characteristics of those skills. We were able to show an improvement among the junior high school students’ ability to identify the components of the human circulatory system, while addressing components at different organizational levels. Interestingly, despite the increase in the number of concepts at each of the organizational levels, the most significant increase was noted in the number of concepts at the macro level and the lowest increase was noted in the number of concepts at the micro level. In addition, an improvement was observed in students’ ability to identify simple relationships and dynamic relationships in a given system. The largest difference was expressed in the number of dynamic relationships that were formed between the system components, thus indicating higher order systems thinking skills. Moreover, an improvement in students’ ability to identify and describe the relationships between a given system’s components can be recognized at all the levels of organization, despite the fact that the most significant increase was noted in the relationships connecting concepts at the same level of organization. Moreover, despite the significant improvement in the number of concepts and relationships in the students’ concept maps, the structure of most students’ concept maps did not advance to a more complex structure following learning.

The circulatory system is considered as one of the most significant five concepts studied in biology education in schools ( 25 ). We therefore chose to characterize systems thinking skills of seventh grade students in the context of this system. The unified model (Table 1 ), and the teaching and learning materials that were developed using this systems thinking model, emphasize the explicit differentiation between components, the processes, and the relationships between them at different levels of organization. This derives from the acknowledgment that the development of systems thinking skills in the context of the human circulatory system may influence students’ perception of every complex biological system. Thus, this perception is essential both for cardiovascular health knowledge development as well as for health knowledge development and decision making skills in the medical field in general. In this way for instance, when teaching the students about the relationships between nutrition and the prevention of atherosclerosis, we can explicitly differentiate between the components at different levels of organization (the circulatory system, the digestive system, arteries, fats etc.), the phenomena related processes (blood vessel wall fat sedimentation, increased blood pressure, endothelial injury etc.), and the relationships between them at various levels of organization.

The unified model for characterizing systems thinking in biology education that was designed especially for this study, is based on three principle theoretical models from the field of systems thinking: (1) systems thinking hierarchical model ( 3 ), (2) systems thinking competence for cell biology education ( 12 ), (3) structure-behavior-function theory ( 8 ). The unified model proved to be a useful tool for developing the teaching and learning materials, for analyzing the students’ concept maps before and following the learning process, as well as in the characterization of the development of students systems thinking skills.

The results of this study suggest that learning based on this unified model, which was developed in the course of this study, may be considered as an efficient tool for the reorganization of knowledge. Knowledge organization is implemented through integrating new knowledge with existing knowledge and updating it. The study results show that at the end of the learning process the students’ glossary regarding the circulatory system increased significantly. The new concepts refer to concepts and processes at all levels of organization. Moreover, students’ knowledge became related and coherent, which indicates a profound understanding of the system. When discussing related knowledge from a system perception the emphasis is on the relations made between the system components and its processes at different levels of organization. Students’ tendencies to attribute great importance to the structural components of a system on the expense of presenting the existing processes and interactions in the system is well known ( 15 , 26 ). It appears that the unified model, which emphasizes the dynamic relationships between the components of the system, was fruitful and the students’ ability to identify dynamic relationships within the system’s components improved significantly following the learning process. In addition, the results indicate that the students’ ability to connect between various levels of organization improved following the learning process, but following the learning process the majority of the relationships formed by the students remained at the macro level. This finding indicates the importance of placing a more significant and explicit emphasis on the relationships between various levels of organization when developing teaching and learning materials and suggests a concept for further research. In the following years in junior high school, namely at the eighth and ninth grades, these students will continue to study about other biological systems namely ecological systems, reproductive systems, and digestive systems in living organisms. It is therefore expected that their ability to analyze systems will further develop.

An additional reported difficulty which was raised in prior research is students’ ability to connect between the circulatory system and the respiratory system ( 16 , 27 ), thus impairing students’ ability to comprehend the system and its function. This study results indicate that many students learned to associate between the two systems and chose to present these relationships in the concept maps summarizing their knowledge on the concept of the human circulatory system. It is important to mention that in this context the idea that the lungs are a crucial part of the circulatory system, is not appropriately mentioned in traditional textbooks ( 6 ). In continuation to this study, it would be interesting to examine the different factors bearing possible effect on students’ systems thinking skills. In this way for instance, we found that many students experienced difficulties making the expected transition from one thinking model to a more advanced thinking model. This difficulty calls for in-depth research that will be focusing on characterizing the students who easily make the transition to a more complex structural model and those who are fixated on a certain thinking model. It will be interesting to examine how the thinking model affects decision making skills regarding health concepts related to the human circulatory system. Furthermore, it will be interesting to examine the class discourse regarding the instruction of biological systems, whilst analyzing the discourse both at the student level and at the class level with regards to their systems thinking skills.

Conflict of Interest Statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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Keywords: systems thinking skills, decision making, circulatory system, teaching and learning materials

Citation: Raved L and Yarden A (2014) Developing seventh grade students’ systems thinking skills in the context of the human circulatory system. Front. Public Health 2 :260. doi: 10.3389/fpubh.2014.00260

Received: 17 August 2014; Accepted: 10 November 2014; Published online: 01 December 2014.

Reviewed by:

Copyright: © 2014 Raved and Yarden. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY) . The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

*Correspondence: Anat Yarden, Department of Science Teaching, Weizmann Institute of Science, Rehovot 76100, Israel e-mail: anat.yarden@weizmann.ac.il

Disclaimer: All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.

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Effect of Concept Mapping Education on Critical Thinking Skills of Medical Students: A Quasi-experimental Study

Aslami maryam.

1 Education Development Center, Quality Improvement Education Research Center, Shiraz university of Medical Sciences, Shiraz, Iran

Dehghani Mohammadreza

Shakurnia abdolhussein.

2 Department of Immunology, school of medicine, Ahvaz Jundishapur university of Medical Sciences, Ahvaz, Iran

Ramezani Ghobad

3 Center for Educational Research in Medical Sciences (CERMS), Department of Medical Education, School of Medicine, Iran University of Medical Sciences (IUMS), Tehran, Iran

Kojuri Javad

Fostering critical thinking (CT) is one of the most important missions in medical education. Concept mapping is a method used to plan and create medical care through a diagrammatic representation of patient problems and medical interventions. Concept mapping as a general method can be used to improve CT skills in medical students. The aim of this study was to explore the effect of concept mapping on CT skills of medical students.

This quasi-experimental study was conducted on 100 second-year medical students which take an anatomy course. Participants were randomly assigned into a control group (lecture-based) and an intervention group (concept mapping). CT levels of medical students were assessed using the California Critical Thinking Skills Test. Data were analyzed using independent sample t-test.

Before intervention, CT scores of the intervention and control groups were 6.68 ± 2.55 and 6.64 ±2.74, respectively, and after intervention, they were 11.64 ±2.29 and 10.04 ± 3.11, respectively. Comparison of mean score differences for both groups before and after intervention demonstrated that CT scores in the experimental group significantly increased after intervention (P=0.021).

Conclusions

Medical students who were taught through concept mapping showed an increase in CT scores, compared with those in the control group. Medical students require effective CT skills in order to make sound knowledge-based assessment and treatment choices during patient care. Therefore, instructors and planners of medical education are expected to apply this educational strategy for developing CT skills in medical students.

Introduction

Concept mapping (CM) is a technique developed by Joseph in the 1970s for visualizing the relationships among different concepts. CM is among the academic teaching strategies that have proven to be useful, in the development of active learning. A great number of studies have been conducted on the effectiveness of CM in fostering critical thinking skills ( 1 , 2 ).

Critical thinking (CT) skill can be defined as “the ability to apply higher cognitive skills (e.g., analysis, synthesis, self-reflection, and perspective taking) and or the ability to be open-minded and intellectually honest”. Critical thinking skill is the most important skill every physician needs, because the complex nature of providing healthcare requires physicians to d gather data, integrate and act upon constantly. This skill plays an essential role in the physician's clinical decision making, which is important in ensuring diagnostic accuracy, appropriate patient management and patient outcomes ( 3 , 4 ).

CT is very important in the medical field because it is t what physicians use to prioritize and make key decisions that can save lives. CT skills of physicians can really mean the difference between someone's life and death. Deficits in CT among physicians have significant implications for patients, including misdiagnosis, delays in diagnosis, treatment errors, lack of patient centered care or recognition of changes in clinical status ( 5 , 6 ). United Nations Educational, Scientific and Cultural Organization (UNESCO) believes that CT provides students with an up-to-date training system. This is why medical universities and their educators need to develop a medical curriculum that will foster CT skills among medical students ( 7 ).

Currently, universities in Iran are still relying on old traditional methods to teach medical students. During the last decade in Iran, medical educators w experienced challenges in providing students with appropriate curricula. They suggested that Iranian medical universities need to change their curriculum from focus on conventional teaching methods. Conventional teaching methods are subject-based, and teachers try to achieve learning objectives through large group lectures. In Lecture Based Learning (LBL), students are passively exposed to factual knowledge and do not learn or apply concepts. However, medical education is moving away from teacher-centered approaches and is incorporating more active learning methods. Active learning process can help foster students' critical thinking skills ( 8 – 10 ).

As researchers were experiencing difficulty with the active learning methods, they were looking for a learning method that will allow students to retain large amounts of information, integrate critical thinking skills, and solve complex clinical problems. CM has been recognized as an effective educational tool that has been used for over 25 years, and a growing body of literature indicates that its t usage in medical education is increasing ( 11 ).

CM is a useful learning tool that creates the opportunity to promote CT skills by providing students opportunities to learn in a meaningful way. This method has helped students to score better on problem solving tests that require recall, transfer and application of knowledge. The map allows students to demonstrate holistic knowledge of a certain topic by showing how concepts on the map are interrelated ( 12 , 13 ).

CM is one of the most effective teaching strategies whose effect on promoting CT has frequently been explored and confirmed. It is a schematic system representing a set of concepts embedded in a framework of propositions. In other words, it is a diagram that shows multiple relationships among concepts ( 14 ). There are two prominent methods that medical students can use to create concept maps to promote meaningful learning. The first method requires students to construct their own maps by creating linking phrases between concepts. On the other hand, the other method, which is referred to as the scaffolding expert maps requires students to fill in blank spaces. This latter is effective for introducing students to CM. As it accurately reflects the knowledge structure of learners, it is more effective in demonstrating students' misunderstanding and misconceptions, it allows students to show how much they have learned, and it uses higher order cognitive processes, such as explaining and reasoning. Theorists believe the lower cognitive load associated with scaffold maps allows the learner to have a sharper focus on concepts involved ( 15 ).

Researchers have reported conflicting results about the effect of CM on increasing students' CT skills ( 16 – 18 ). Further studies are i required to clarify this issue. The purpose of this study was to determine if CM is more effective in teaching medical students anatomy topics compared to traditional lecturing method. We predict that students taught through concept map method will score better on California CT Test compared to students taught through traditional lecturing methods.

Materials and Methods

Study design and participants : This was a two-group quasi-experimental study with a pre- and post-test design. Participants consisted of a total of 108 second-year medical students who were enrolled in Ahvaz Jundishapur University of Medical Sciences (AJUMS) attending an anatomy course in 2017. This course was offered in the third semester of the second-year program in a 12-week course on medical anatomy. None of the participants had previous experience in the use of CM in their curriculum. A research assistant explained the nature and purpose of the study for the participants. All medical students voluntarily took part and signed an informed consent. Codes were provided to participants for the demographic survey to ensure data confidentiality. Participants were provided with detailed verbal and written explanations of the study and were told that they could withdraw from the study at any time. They were also assured that their participation in the research would not affect their success in the course.

Before starting the course classes, the study sample (108 students) was randomly divided into two equal groups, 54 each. One group was considered as the intervention group (concept mapping) and the other was considered as the control group (lecture). The intervention group was taught through concept mapping, while the control group was taught by traditional didactic lecturing alone. The study was conducted for over 12 weeks, starting on September 2017. In the 1st week of the semester, pre-testing of the students' critical thinking skills in both experimental and control groups was done using California critical thinking Skills Test, form B (CCTST form B), before implementation of CM to identify their critical thinking level. It consisted of 34 multiple choice questions designed for the assessment of CT skills. In this test, each correct answer represents one score. The minimum and maximum obtainable scores are 0 and 34, respectively ( 19 ). In Iran, the reliability and validity of this test have already been determined and confirmed ( 20 ).

During the first week of the course, in a 2-hour session, the students in the intervention group were taught how to construct a concept map and how to use it appropriately in the context of anatomy. The students in the intervention group were required to present their discussion findings using the CM technique. Every student was required to prepare a concept map for all the presented topics. In each training session, the maps were assessed by the researcher, and the students were given feedback. Participants compared similarities and differences between their concept maps to assist in development of their individual concept map during their anatomy class. Training of the control group was done through traditional lecture method using power point software. The students of both groups passed 12 sessions of “anatomy course” in 12 consecutive weeks in lecture and CM methods, respectively.

A concept map is a diagram that visually illustrates relationships between concepts and ideas. Concept maps are free of color and pictures, and are constructed in a top-to-bottom hierarchy. Most concept maps illustrate ideas as boxes or circles, which are structured hierarchically and connected with lines. These lines are labeled with linking words to help explain the connections between concepts. An example of a mind map created by a medical student in this study can be seen in Figure 1 .

Student concept map. An example of a concept map from one of the medical students in this study

At the end of the semester in the 12th week, a post-test was conducted for both experimental and control groups by administering the CCTST (form B). The results of the pre- and the post-tests of the two groups were compared to assess the effect of using CM on increasing the students' critical thinking skills. To this aim, the difference between the mean of CT scores before and after intervention in each group was calculated and then the differences between the two groups were analyzed.

The room and time of the anatomy class were different for the two groups, but despite this, the students were in contact with each other in college and dormitory. Therefore, they may have exchanged concept map information with each other.

Data analysis was done using SPSS version 16. Descriptive statistics for some data such as gender, age and GPA was computed using frequencies, percentages, mean and standard deviation. Student characteristics were described, chi-square tests of differences between groups were conducted for categorical variables, and t-tests were performed for continuous variables. Two-group independent t-tests compared the CT scores at the beginning and end of the course between the two measurements.

Out of the 108 subjects participating in the study, 100 completed the questionnaire and returned it (response rate 92.6%). Table 1 presents the students' demographic characteristics. Subjects were homogenous in terms of gender, age and GPA. In the experimental group, 60% of subjects were females and 40% were males. In the control group, 54% were females and 46% were males. Sex distribution was similar in both groups (p=0.34). The mean age of medical students in both groups was also similar. In the experimental group, the mean age of subjects was 20.96 years (SD =0.88) and in the control group, it was 20.90 years (SD = 0.84). No significant differences were found between the control and experimental groups regarding age (p= 0.53). The grade point average (GPA) of previous semesters of experimental group was 15.20 (SD = 1.24) and that of the control group was 15.46 (SD = 1.17). In relation to students' GPA, chi-square test did not reveal a significant difference between the two groups (p=0.280).

Students' characteristics in two different experimental and control groups

The analysis scores of CT skills before intervention among both groups revealed that the mean CT scores of experimental and control groups were 6.64 and 6.68, respectively. The scores of experimental group before intervention ranged from 2 to 13 and that of the control group from 2 to 12 ( Figure 2 ).

Critical thinking scores of the control group before and after intervention

The mean CT scores after intervention among the experimental and control group were found to be 10.04 and 11.64, respectively. The post intervention scores ranged from 8 to 17 in the experimental group and from 3 to 16 in the control group ( Figure 3 ).

Critical thinking scores of the experimental group before and after intervention

Table 2 demonstrates the students' CT skills by group. As shown in Table 2 , before intervention, scores of CT skills in the intervention and control groups did not differ, which indicates that the students' performance was similar when they started the course. However, after intervention, CT scores were significantly higher in the intervention group. Students in the intervention group performed much better on the CT levels than students in the control group (P=0.004).

Comparison of mean and SD of critical thinking skills in experimental and control groups before and after the intervention

The average score obtained in anatomy course at the final exam by the entire medical student group was 5.98. The average score obtained in anatomy course by the experimental group was 6.38 and that of the control group was 5.58 (out of 10). There was a statistically significant difference between the two groups (t=2.67, p=0.009).

This study examined the impact of concept mapping on CT skills in the medical students in an anatomy course. The findings indicated that the use of CM had a positive effect on CT skills. This improvement could be achieved as a result of the teaching anatomy course using CM as a learning method. Researchers believe map construction is a useful tool that helps students to develop clinical reasoning skills through additional focus on logic, and it probably stimulates the use of thinking skills, such as analysis, interpretation, and evaluation, and finally promotes the development of CT skills ( 21 ).

The findings of our study are consistent with those of Kaddoura and Yang (2016) who analyzed the impact of a concept map teaching approach on nursing students' CT in the context of pathophysiology and pharmacology. Kaddoura and Yang integrated concept map teaching strategies in courses in order to develop CT skills in their students. They found that using CM in the education of nursing students leads to development of CT skills ( 22 ). A recent study was done by Sarhangi et al. on Iranian nursing students, indicating that the CM had a positive effect on CT skills ( 23 ). The result of a review article also indicated that CM affects the CT affective dispositions and CT cognitive skills ( 24 ).

Correspondingly, the findings of this study are also consistent with those of Nirmala et al. (2011), Deshatty et al. (2013), Moattari et al. (2014), Orique and McCarthy (2015), Mohamed (2017), and Elasrag (2020), who explored the effects of CM in promoting CT skills ( 2 , 14 , 25 – 28 ). These researchers concluded that CM is an effective strategy for improving students' ability to think critically.

In a systematic review on the use of CM in Iran, it was reported that CM had an important effect on improvement of critical thinking skills ( 29 ). The reason CT skills are promoted in CM is due to the fact that in this method, the learner has an active role in his/her own learning, which leads to promotion of high level learning. In this regard, these active interactions between learner/instructor and apparent organizing of the concepts allow the learner and instructor to exchange their perspective on how to communicate internal concepts, and they also would be able to discover missing concepts and communications, determine new educational needs, and restart the realignment of the map, which is the very self-assessment process that is part of the main CT skills ( 1 ). CM can be used in medical education in order to provide comprehensive and patient-centered care, prepare the medical students for clinical processes and make a connection between theory and clinical courses. Therefore, considering the advantages of this method in terms of increasing higher learning level and increasing medical students' motivation for learning, using this method in a more practical way in medical students' education is recommended.

However, our study findings are inconsistent with those of Bixler et al. (2015) who attempted to improve CT skill among fourth-year medical students using small group concept mapping ( 30 ). They found no significant increase in CT skills from pre-test to post-test when medical students were educated using a CM method. They proposed that the short time and the limited number of topics to which CM was applied may not provide a sufficient dose to impart a significant improvement on the CT Skills.

Our findings were also inconsistent with those of D'Antoniin et.al (2010) who conducted a quasi-experimental study to determine the effect of CM on CT skills in first-year medical students ( 31 ). They found no significant differences between the pre-test and post-test scores of the medical students for CT skills. D'Antoniin et al proposed that there may be a dose effect for using concept mapping, that is, more practice across more different kinds of scenarios may be required to equip students in this complex skill. Of course, this hypothesis requires further studies. Abdoli demonstrated that overall mean CT was not statistically significant after intervention for nursing students in their fourth semester at Isfahan University ( 32 ). He argued that perhaps one semester of using CM may not be sufficient to measure the effects of CM on the CT skill of students.

Researchers believe that absence of significance increase in overall CT scores after intervention might be derived from several factors related to the circumstances under which the study is conducted, the participants' conception and comfort level with participating in the study, seriousness in taking tests, the brevity of the experiment, and participants' developmental stages. In addition, it may be because that a training course alone is not significantly correlated with the critical thinking, because acquiring critical thinking skills needs a long period of time and continuing education ( 14 , 33 ).

Although there was a significant improvement in the CT skills among the experimental group, the overall scores of the experimental and the control groups were found to be very poor. The reason for the poor CT scores in students needs to be explored in a separate study. These findings were supported by Mohamed et al. (2017), who conducted a study for improving critical thinking of nursing students by the implementation of CM in Cairo University, Egypt. They reported low scores of critical thinking and added that low scores of critical thinking among their study subjects can be attributed to the educational system followed in secondary schools in Egypt ( 14 ). It is mainly a pedagogical approach with traditional teacher-centered rather than student-centered learning, where the student is mostly a passive recipient. Such a traditional educational approach does not foster CT skills in students.

The current study also revealed that CM not only leads to improved CT skills in medical students, but also causes a significant increase in students' scores in anatomy course. Indeed, anatomy topics can be effectively incorporated into concept map, making it easier for medical students to learn anatomy topics. Students being taught anatomy topics through concept map method had higher scores on anatomy course compared to students in the traditional lecturing group. This suggests that concept map is an effective educational tool and should be incorporated into medical education curriculum because it encourages students to become more independent learners and enhances learning of medical courses.

Improving high levels of thinking skills as one of the important missions of medical education makes it necessary to use appropriate approaches for developing CT skills. Most of the research conducted on the effectiveness of concept maps in medical education has focused primarily on the nursing population ( 24 ). However, our study included a sample of medical students. There are few studies similar to ours that have taught the intervention group concept map and then reevaluated students' CT skills. This study builds on previous work to suggest that CM is an effective strategy for developing medical students' ability to think critically. Using CM in the education of medical students appears to predict the improvement of CT skills, which is one of the most important missions of medical education. It is recommended that program directors and medical faculties evaluate their curricula to integrate concept map teaching strategies in other clinical courses to improve CT abilities in their students.

A limitation of this study was the small sample size and examining only one group of students (medical students). Another limitation was the use of only one course of medical program. In addition, since CM education is not used in other medical schools in Iran, the results of the study cannot be generalized to all medical students. We recommend that future researchers design a study with a larger sample size that includes other fields of medical sciences such as dentistry and pharmacy. Due to inability to keep interactions between the students during practicum under control, the students were likely to influence each other while creating concept maps. For future studies, it would be valuable to use a blinded study design to control for the interaction between experimental and control groups. This will help to reduce information exchange between both groups.

The finding of the current study showed an increase in CT scores in the experimental group as compared to the control group. Therefore, it can be concluded that CM strategy can promote critical thinking skills compared with traditional methods. Accordingly, instructors and curriculum planners are expected to apply this educational strategy for developing CT skills in medical students. The results also suggest that medical curricula need to change based on a student-centered learning approach.

The following recommendations are suggested as implications for future research:

• A longitudinal study is recommended that uses CM throughout the whole medical program curriculum, not just one course; it would be a more effective measure of the actual effect of CM on CT skill of medical students over time.
• In addition, it is recommended that a comprehensive study be replicated with a larger sample size, and randomly select from multiple different medical schools, in order to provide a more accurate representation of medical students.
• A number of participants withdrew during the second stage of the study due to the challenges with administering California Critical Thinking Questionnaire. Future research, should address the challenges associated with administering the California Critical Thinking Questionnaire in order to reduce participant attrition rate.
• Finally, we recommend researchers to explain the benefits and advantages of this study to participants prior to the start of their study.

This study was approved by Ethics Committee of Shiraz University of Medical Sciences (Ethics Code of: IR.SUMS.REC.F1202).

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Circulatory system – A Visual Representation using Mind Map

What is a Mind Map?

Steps to create Mind Maps

• Begin with the main concept in the center
• Select keywords and concepts related to the main topic and enter these as child items.
• Keep the mind map clear using hierarchy, numerical order, etc. to indicate the branches.
• The central lines should be thicker and flowing. It becomes progressively thinner as it spreads out from the center.

Benefits of mind mapping

• Helps meaningful learning
• It’s a more engaging form of learning
• Makes complex issues easier to understand
• Helps in memorizing and retaining data
• It improves creativity
• Improves writing skills
• Improves productivity

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20.5 Circulatory Pathways

Learning objectives.

By the end of this section, you will be able to:

• Identify the vessels through which blood travels within the pulmonary circuit, beginning from the right ventricle of the heart and ending at the left atrium
• Create a flow chart showing the major systemic arteries through which blood travels from the aorta and its major branches, to the most significant arteries feeding into the right and left upper and lower limbs
• Create a flow chart showing the major systemic veins through which blood travels from the feet to the right atrium of the heart

Virtually every cell, tissue, organ, and system in the body is impacted by the circulatory system. This includes the generalized and more specialized functions of transport of materials, capillary exchange, maintaining health by transporting white blood cells and various immunoglobulins (antibodies), hemostasis, regulation of body temperature, and helping to maintain acid-base balance. In addition to these shared functions, many systems enjoy a unique relationship with the circulatory system. Figure 20.22 summarizes these relationships.

As you learn about the vessels of the systemic and pulmonary circuits, notice that many arteries and veins share the same names, parallel one another throughout the body, and are very similar on the right and left sides of the body. These pairs of vessels will be traced through only one side of the body. Where differences occur in branching patterns or when vessels are singular, this will be indicated. For example, you will find a pair of femoral arteries and a pair of femoral veins, with one vessel on each side of the body. In contrast, some vessels closer to the midline of the body, such as the aorta, are unique. Moreover, some superficial veins, such as the great saphenous vein in the femoral region, have no arterial counterpart. Another phenomenon that can make the study of vessels challenging is that names of vessels can change with location. Like a street that changes name as it passes through an intersection, an artery or vein can change names as it passes an anatomical landmark. For example, the left subclavian artery becomes the axillary artery as it passes through the body wall and into the axillary region, and then becomes the brachial artery as it flows from the axillary region into the upper arm (or brachium). You will also find examples of anastomoses where two blood vessels that previously branched reconnect. Anastomoses are especially common in veins, where they help maintain blood flow even when one vessel is blocked or narrowed, although there are some important ones in the arteries supplying the brain.

As you read about circular pathways, notice that there is an occasional, very large artery referred to as a trunk , a term indicating that the vessel gives rise to several smaller arteries. For example, the celiac trunk gives rise to the left gastric, common hepatic, and splenic arteries.

As you study this section, imagine you are on a “Voyage of Discovery” similar to Lewis and Clark’s expedition in 1804–1806, which followed rivers and streams through unfamiliar territory, seeking a water route from the Atlantic to the Pacific Ocean. You might envision being inside a miniature boat, exploring the various branches of the circulatory system. This simple approach has proven effective for many students in mastering these major circulatory patterns. Another approach that works well for many students is to create simple line drawings similar to the ones provided, labeling each of the major vessels. It is beyond the scope of this text to name every vessel in the body. However, we will attempt to discuss the major pathways for blood and acquaint you with the major named arteries and veins in the body. Also, please keep in mind that individual variations in circulation patterns are not uncommon.

Interactive Link

Visit this site for a brief summary of the arteries.

Pulmonary Circulation

Recall that blood returning from the systemic circuit enters the right atrium ( Figure 20.23 ) via the superior and inferior venae cavae and the coronary sinus, which drains the blood supply of the heart muscle. These vessels will be described more fully later in this section. This blood is relatively low in oxygen and relatively high in carbon dioxide, since much of the oxygen has been extracted for use by the tissues and the waste gas carbon dioxide was picked up to be transported to the lungs for elimination. From the right atrium, blood moves into the right ventricle, which pumps it to the lungs for gas exchange. This system of vessels is referred to as the pulmonary circuit .

The single vessel exiting the right ventricle is the pulmonary trunk . At the base of the pulmonary trunk is the pulmonary semilunar valve, which prevents backflow of blood into the right ventricle during ventricular diastole. As the pulmonary trunk reaches the superior surface of the heart, it curves posteriorly and rapidly bifurcates (divides) into two branches, a left and a right pulmonary artery . To prevent confusion between these vessels, it is important to refer to the vessel exiting the heart as the pulmonary trunk, rather than also calling it a pulmonary artery. The pulmonary arteries in turn branch many times within the lung, forming a series of smaller arteries and arterioles that eventually lead to the pulmonary capillaries. The pulmonary capillaries surround lung structures known as alveoli that are the sites of oxygen and carbon dioxide exchange.

Once gas exchange is completed, oxygenated blood flows from the pulmonary capillaries into a series of pulmonary venules that eventually lead to a series of larger pulmonary veins . Four pulmonary veins, two on the left and two on the right, return blood to the left atrium. At this point, the pulmonary circuit is complete. Table 20.4 defines the major arteries and veins of the pulmonary circuit discussed in the text.

Overview of Systemic Arteries

Blood relatively high in oxygen concentration is returned from the pulmonary circuit to the left atrium via the four pulmonary veins. From the left atrium, blood moves into the left ventricle, which pumps blood into the aorta. The aorta and its branches—the systemic arteries—send blood to virtually every organ of the body ( Figure 20.24 ).

The aorta is the largest artery in the body ( Figure 20.25 ). It arises from the left ventricle and eventually descends to the abdominal region, where it bifurcates at the level of the fourth lumbar vertebra into the two common iliac arteries. The aorta consists of the ascending aorta, the aortic arch, and the descending aorta, which passes through the diaphragm and a landmark that divides into the superior thoracic and inferior abdominal components. Arteries originating from the aorta ultimately distribute blood to virtually all tissues of the body. At the base of the aorta is the aortic semilunar valve that prevents backflow of blood into the left ventricle while the heart is relaxing. After exiting the heart, the ascending aorta moves in a superior direction for approximately 5 cm and ends at the sternal angle. Following this ascent, it reverses direction, forming a graceful arc to the left, called the aortic arch . The aortic arch descends toward the inferior portions of the body and ends at the level of the intervertebral disk between the fourth and fifth thoracic vertebrae. Beyond this point, the descending aorta continues close to the bodies of the vertebrae and passes through an opening in the diaphragm known as the aortic hiatus . Superior to the diaphragm, the aorta is called the thoracic aorta , and inferior to the diaphragm, it is called the abdominal aorta . The abdominal aorta terminates when it bifurcates into the two common iliac arteries at the level of the fourth lumbar vertebra. See Figure 20.25 for an illustration of the ascending aorta, the aortic arch, and the initial segment of the descending aorta plus major branches; Table 20.5 summarizes the structures of the aorta.

Coronary Circulation

The first vessels that branch from the ascending aorta are the paired coronary arteries (see Figure 20.25 ), which arise from two of the three sinuses in the ascending aorta just superior to the aortic semilunar valve. These sinuses contain the aortic baroreceptors and chemoreceptors critical to maintain cardiac function. The left coronary artery arises from the left posterior aortic sinus. The right coronary artery arises from the anterior aortic sinus. Normally, the right posterior aortic sinus does not give rise to a vessel.

The coronary arteries encircle the heart, forming a ring-like structure that divides into the next level of branches that supplies blood to the heart tissues. (Seek additional content for more detail on cardiac circulation.)

Aortic Arch Branches

There are three major branches of the aortic arch: the brachiocephalic artery, the left common carotid artery, and the left subclavian (literally “under the clavicle”) artery. As you would expect based upon proximity to the heart, each of these vessels is classified as an elastic artery.

The brachiocephalic artery is located only on the right side of the body; there is no corresponding artery on the left. The brachiocephalic artery branches into the right subclavian artery and the right common carotid artery. The left subclavian and left common carotid arteries arise independently from the aortic arch but otherwise follow a similar pattern and distribution to the corresponding arteries on the right side (see Figure 20.23 ).

Each subclavian artery supplies blood to the arms, chest, shoulders, back, and central nervous system. It then gives rise to three major branches: the internal thoracic artery, the vertebral artery, and the thyrocervical artery. The internal thoracic artery , or mammary artery, supplies blood to the thymus, the pericardium of the heart, and the anterior chest wall. The vertebral artery passes through the vertebral foramen in the cervical vertebrae and then through the foramen magnum into the cranial cavity to supply blood to the brain and spinal cord. The paired vertebral arteries join together to form the large basilar artery at the base of the medulla oblongata. This is an example of an anastomosis. The subclavian artery also gives rise to the thyrocervical artery that provides blood to the thyroid, the cervical region of the neck, and the upper back and shoulder.

The common carotid artery divides into internal and external carotid arteries. The right common carotid artery arises from the brachiocephalic artery and the left common carotid artery arises directly from the aortic arch. The external carotid artery supplies blood to numerous structures within the face, lower jaw, neck, esophagus, and larynx. These branches include the lingual, facial, occipital, maxillary, and superficial temporal arteries. The internal carotid artery initially forms an expansion known as the carotid sinus, containing the carotid baroreceptors and chemoreceptors. Like their counterparts in the aortic sinuses, the information provided by these receptors is critical to maintaining cardiovascular homeostasis (see Figure 20.23 ).

The internal carotid arteries along with the vertebral arteries are the two primary suppliers of blood to the human brain. Given the central role and vital importance of the brain to life, it is critical that blood supply to this organ remains uninterrupted. Recall that blood flow to the brain is remarkably constant, with approximately 20 percent of blood flow directed to this organ at any given time. When blood flow is interrupted, even for just a few seconds, a transient ischemic attack (TIA) , or mini-stroke, may occur, resulting in loss of consciousness or temporary loss of neurological function. In some cases, the damage may be permanent. Loss of blood flow for longer periods, typically between 3 and 4 minutes, will likely produce irreversible brain damage or a stroke, also called a cerebrovascular accident (CVA) . The locations of the arteries in the brain not only provide blood flow to the brain tissue but also prevent interruption in the flow of blood. Both the carotid and vertebral arteries branch once they enter the cranial cavity, and some of these branches form a structure known as the arterial circle (or circle of Willis ), an anastomosis that is remarkably like a traffic circle that sends off branches (in this case, arterial branches to the brain). As a rule, branches to the anterior portion of the cerebrum are normally fed by the internal carotid arteries; the remainder of the brain receives blood flow from branches associated with the vertebral arteries.

The internal carotid artery continues through the carotid canal of the temporal bone and enters the base of the brain through the carotid foramen where it gives rise to several branches ( Figure 20.26 and Figure 20.27 ). One of these branches is the anterior cerebral artery that supplies blood to the frontal lobe of the cerebrum. Another branch, the middle cerebral artery , supplies blood to the temporal and parietal lobes, which are the most common sites of CVAs. The ophthalmic artery , the third major branch, provides blood to the eyes.

The right and left anterior cerebral arteries join together to form an anastomosis called the anterior communicating artery . The initial segments of the anterior cerebral arteries and the anterior communicating artery form the anterior portion of the arterial circle. The posterior portion of the arterial circle is formed by a left and a right posterior communicating artery that branches from the posterior cerebral artery , which arises from the basilar artery. It provides blood to the posterior portion of the cerebrum and brain stem. The basilar artery is an anastomosis that begins at the junction of the two vertebral arteries and sends branches to the cerebellum and brain stem. It flows into the posterior cerebral arteries. Table 20.6 summarizes the aortic arch branches, including the major branches supplying the brain.

Thoracic Aorta and Major Branches

The thoracic aorta begins at the level of vertebra T5 and continues through to the diaphragm at the level of T12, initially traveling within the mediastinum to the left of the vertebral column. As it passes through the thoracic region, the thoracic aorta gives rise to several branches, which are collectively referred to as visceral branches and parietal branches ( Figure 20.28 ). Those branches that supply blood primarily to visceral organs are known as the visceral branches and include the bronchial arteries, pericardial arteries, esophageal arteries, and the mediastinal arteries, each named after the tissues it supplies. Each bronchial artery (typically two on the left and one on the right) supplies systemic blood to the lungs and visceral pleura, in addition to the blood pumped to the lungs for oxygenation via the pulmonary circuit. The bronchial arteries follow the same path as the respiratory branches, beginning with the bronchi and ending with the bronchioles. There is considerable, but not total, intermingling of the systemic and pulmonary blood at anastomoses in the smaller branches of the lungs. This may sound incongruous—that is, the mixing of systemic arterial blood high in oxygen with the pulmonary arterial blood lower in oxygen—but the systemic vessels also deliver nutrients to the lung tissue just as they do elsewhere in the body. The mixed blood drains into typical pulmonary veins, whereas the bronchial artery branches remain separate and drain into bronchial veins described later. Each pericardial artery supplies blood to the pericardium, the esophageal artery provides blood to the esophagus, and the mediastinal artery provides blood to the mediastinum. The remaining thoracic aorta branches are collectively referred to as parietal branches or somatic branches, and include the intercostal and superior phrenic arteries. Each intercostal artery provides blood to the muscles of the thoracic cavity and vertebral column. The superior phrenic artery provides blood to the superior surface of the diaphragm. Table 20.7 lists the arteries of the thoracic region.

Abdominal Aorta and Major Branches

After crossing through the diaphragm at the aortic hiatus, the thoracic aorta is called the abdominal aorta (see Figure 20.28 ). This vessel remains to the left of the vertebral column and is embedded in adipose tissue behind the peritoneal cavity. It formally ends at approximately the level of vertebra L4, where it bifurcates to form the common iliac arteries. Before this division, the abdominal aorta gives rise to several important branches. A single celiac trunk (artery) emerges and divides into the left gastric artery to supply blood to the stomach and esophagus, the splenic artery to supply blood to the spleen, and the common hepatic artery , which in turn gives rise to the hepatic artery proper to supply blood to the liver, the right gastric artery to supply blood to the stomach, the cystic artery to supply blood to the gall bladder, and several branches, one to supply blood to the duodenum and another to supply blood to the pancreas. Two additional single vessels arise from the abdominal aorta. These are the superior and inferior mesenteric arteries. The superior mesenteric artery arises approximately 2.5 cm after the celiac trunk and branches into several major vessels that supply blood to the small intestine (duodenum, jejunum, and ileum), the pancreas, and a majority of the large intestine. The inferior mesenteric artery supplies blood to the distal segment of the large intestine, including the rectum. It arises approximately 5 cm superior to the common iliac arteries.

In addition to these single branches, the abdominal aorta gives rise to several significant paired arteries along the way. These include the inferior phrenic arteries, the adrenal arteries, the renal arteries, the gonadal arteries, and the lumbar arteries. Each inferior phrenic artery is a counterpart of a superior phrenic artery and supplies blood to the inferior surface of the diaphragm. The adrenal artery supplies blood to the adrenal (suprarenal) glands and arises near the superior mesenteric artery. Each renal artery branches approximately 2.5 cm inferior to the superior mesenteric arteries and supplies a kidney. The right renal artery is longer than the left since the aorta lies to the left of the vertebral column and the vessel must travel a greater distance to reach its target. Renal arteries branch repeatedly to supply blood to the kidneys. Each gonadal artery supplies blood to the gonads, or reproductive organs, and is also described as either an ovarian artery or a testicular artery (internal spermatic), depending upon the sex of the individual. An ovarian artery supplies blood to an ovary, uterine (Fallopian) tube, and the uterus, and is located within the suspensory ligament of the uterus. It is considerably shorter than a testicular artery , which ultimately travels outside the body cavity to the testes, forming one component of the spermatic cord. The gonadal arteries arise inferior to the renal arteries and are generally retroperitoneal. The ovarian artery continues to the uterus where it forms an anastomosis with the uterine artery that supplies blood to the uterus. Both the uterine arteries and vaginal arteries, which distribute blood to the vagina, are branches of the internal iliac artery. The four paired lumbar arteries are the counterparts of the intercostal arteries and supply blood to the lumbar region, the abdominal wall, and the spinal cord. In some instances, a fifth pair of lumbar arteries emerges from the median sacral artery.

The aorta divides at approximately the level of vertebra L4 into a left and a right common iliac artery but continues as a small vessel, the median sacral artery , into the sacrum. The common iliac arteries provide blood to the pelvic region and ultimately to the lower limbs. They split into external and internal iliac arteries approximately at the level of the lumbar-sacral articulation. Each internal iliac artery sends branches to the urinary bladder, the walls of the pelvis, the external genitalia, and the medial portion of the femoral region. In females, they also provide blood to the uterus and vagina. The much larger external iliac artery supplies blood to each of the lower limbs. Figure 20.29 shows the distribution of the major branches of the aorta into the thoracic and abdominal regions. Figure 20.30 shows the distribution of the major branches of the common iliac arteries. Table 20.8 summarizes the major branches of the abdominal aorta.

Arteries Serving the Upper Limbs

As the subclavian artery exits the thorax into the axillary region, it is renamed the axillary artery . Although it does branch and supply blood to the region near the head of the humerus (via the humeral circumflex arteries), the majority of the vessel continues into the upper arm, or brachium, and becomes the brachial artery ( Figure 20.31 ). The brachial artery supplies blood to much of the brachial region and divides at the elbow into several smaller branches, including the deep brachial arteries, which provide blood to the posterior surface of the arm, and the ulnar collateral arteries, which supply blood to the region of the elbow. As the brachial artery approaches the coronoid fossa, it bifurcates into the radial and ulnar arteries, which continue into the forearm, or antebrachium. The radial artery and ulnar artery parallel their namesake bones, giving off smaller branches until they reach the wrist, or carpal region. At this level, they fuse to form the superficial and deep palmar arches that supply blood to the hand, as well as the digital arteries that supply blood to the digits. Figure 20.32 shows the distribution of systemic arteries from the heart into the upper limb. Table 20.9 summarizes the arteries serving the upper limbs.

Arteries Serving the Lower Limbs

The external iliac artery exits the body cavity and enters the femoral region of the lower leg ( Figure 20.33 ). As it passes through the body wall, it is renamed the femoral artery . It gives off several smaller branches as well as the lateral deep femoral artery that in turn gives rise to a lateral circumflex artery . These arteries supply blood to the deep muscles of the thigh as well as ventral and lateral regions of the integument. The femoral artery also gives rise to the genicular artery , which provides blood to the region of the knee. As the femoral artery passes posterior to the knee near the popliteal fossa, it is called the popliteal artery. The popliteal artery branches into the anterior and posterior tibial arteries.

The anterior tibial artery is located between the tibia and fibula, and supplies blood to the muscles and integument of the anterior tibial region. Upon reaching the tarsal region, it becomes the dorsalis pedis artery , which branches repeatedly and provides blood to the tarsal and dorsal regions of the foot. The posterior tibial artery provides blood to the muscles and integument on the posterior surface of the tibial region. The fibular or peroneal artery branches from the posterior tibial artery. It bifurcates and becomes the medial plantar artery and lateral plantar artery , providing blood to the plantar surfaces. There is an anastomosis with the dorsalis pedis artery, and the medial and lateral plantar arteries form two arches called the dorsal arch (also called the arcuate arch) and the plantar arch , which provide blood to the remainder of the foot and toes. Figure 20.34 shows the distribution of the major systemic arteries in the lower limb. Table 20.10 summarizes the major systemic arteries discussed in the text.

Overview of Systemic Veins

Systemic veins return blood to the right atrium. Since the blood has already passed through the systemic capillaries, it will be relatively low in oxygen concentration. In many cases, there will be veins draining organs and regions of the body with the same name as the arteries that supplied these regions and the two often parallel one another. This is often described as a “complementary” pattern. However, there is a great deal more variability in the venous circulation than normally occurs in the arteries. For the sake of brevity and clarity, this text will discuss only the most commonly encountered patterns. However, keep this variation in mind when you move from the classroom to clinical practice.

In both the neck and limb regions, there are often both superficial and deeper levels of veins. The deeper veins generally correspond to the complementary arteries. The superficial veins do not normally have direct arterial counterparts, but in addition to returning blood, they also make contributions to the maintenance of body temperature. When the ambient temperature is warm, more blood is diverted to the superficial veins where heat can be more easily dissipated to the environment. In colder weather, there is more constriction of the superficial veins and blood is diverted deeper where the body can retain more of the heat.

The “Voyage of Discovery” analogy and stick drawings mentioned earlier remain valid techniques for the study of systemic veins, but veins present a more difficult challenge because there are numerous anastomoses and multiple branches. It is like following a river with many tributaries and channels, several of which interconnect. Tracing blood flow through arteries follows the current in the direction of blood flow, so that we move from the heart through the large arteries and into the smaller arteries to the capillaries. From the capillaries, we move into the smallest veins and follow the direction of blood flow into larger veins and back to the heart. Figure 20.35 outlines the path of the major systemic veins.

Visit this site for a brief online summary of the veins.

The right atrium receives all of the systemic venous return. Most of the blood flows into either the superior vena cava or inferior vena cava. If you draw an imaginary line at the level of the diaphragm, systemic venous circulation from above that line will generally flow into the superior vena cava; this includes blood from the head, neck, chest, shoulders, and upper limbs. The exception to this is that most venous blood flow from the coronary veins flows directly into the coronary sinus and from there directly into the right atrium. Beneath the diaphragm, systemic venous flow enters the inferior vena cava, that is, blood from the abdominal and pelvic regions and the lower limbs.

The Superior Vena Cava

The superior vena cava drains most of the body superior to the diaphragm ( Figure 20.36 ). On both the left and right sides, the subclavian vein forms when the axillary vein passes through the body wall from the axillary region. It fuses with the external and internal jugular veins from the head and neck to form the brachiocephalic vein . Each vertebral vein also flows into the brachiocephalic vein close to this fusion. These veins arise from the base of the brain and the cervical region of the spinal cord, and flow largely through the intervertebral foramina in the cervical vertebrae. They are the counterparts of the vertebral arteries. Each internal thoracic vein , also known as an internal mammary vein, drains the anterior surface of the chest wall and flows into the brachiocephalic vein.

The remainder of the blood supply from the thorax drains into the azygos vein. Each intercostal vein drains muscles of the thoracic wall, each esophageal vein delivers blood from the inferior portions of the esophagus, each bronchial vein drains the systemic circulation from the lungs, and several smaller veins drain the mediastinal region. Bronchial veins carry approximately 13 percent of the blood that flows into the bronchial arteries; the remainder intermingles with the pulmonary circulation and returns to the heart via the pulmonary veins. These veins flow into the azygos vein , and with the smaller hemiazygos vein (hemi- = “half”) on the left of the vertebral column, drain blood from the thoracic region. The hemiazygos vein does not drain directly into the superior vena cava but enters the brachiocephalic vein via the superior intercostal vein.

The azygos vein passes through the diaphragm from the thoracic cavity on the right side of the vertebral column and begins in the lumbar region of the thoracic cavity. It flows into the superior vena cava at approximately the level of T2, making a significant contribution to the flow of blood. It combines with the two large left and right brachiocephalic veins to form the superior vena cava.

Table 20.11 summarizes the veins of the thoracic region that flow into the superior vena cava.

Veins of the Head and Neck

Blood from the brain and the superficial facial vein flow into each internal jugular vein ( Figure 20.37 ). Blood from the more superficial portions of the head, scalp, and cranial regions, including the temporal vein and maxillary vein , flow into each external jugular vein . Although the external and internal jugular veins are separate vessels, there are anastomoses between them close to the thoracic region. Blood from the external jugular vein empties into the subclavian vein. Table 20.12 summarizes the major veins of the head and neck.

Venous Drainage of the Brain

Circulation to the brain is both critical and complex (see Figure 20.37 ). Many smaller veins of the brain stem and the superficial veins of the cerebrum lead to larger vessels referred to as intracranial sinuses. These include the superior and inferior sagittal sinuses, straight sinus, cavernous sinuses, left and right sinuses, the petrosal sinuses, and the occipital sinuses. Ultimately, sinuses will lead back to either the inferior jugular vein or vertebral vein.

Most of the veins on the superior surface of the cerebrum flow into the largest of the sinuses, the superior sagittal sinus . It is located midsagittally between the meningeal and periosteal layers of the dura mater within the falx cerebri and, at first glance in images or models, can be mistaken for the subarachnoid space. Most reabsorption of cerebrospinal fluid occurs via the chorionic villi (arachnoid granulations) into the superior sagittal sinus. Blood from most of the smaller vessels originating from the inferior cerebral veins flows into the great cerebral vein and into the straight sinus . Other cerebral veins and those from the eye socket flow into the cavernous sinus , which flows into the petrosal sinus and then into the internal jugular vein. The occipital sinus , sagittal sinus, and straight sinuses all flow into the left and right transverse sinuses near the lambdoid suture. The transverse sinuses in turn flow into the sigmoid sinuses that pass through the jugular foramen and into the internal jugular vein. The internal jugular vein flows parallel to the common carotid artery and is more or less its counterpart. It empties into the brachiocephalic vein. The veins draining the cervical vertebrae and the posterior surface of the skull, including some blood from the occipital sinus, flow into the vertebral veins. These parallel the vertebral arteries and travel through the transverse foramina of the cervical vertebrae. The vertebral veins also flow into the brachiocephalic veins. Table 20.13 summarizes the major veins of the brain.

Veins Draining the Upper Limbs

The digital veins in the fingers come together in the hand to form the palmar venous arches ( Figure 20.38 ). From here, the veins come together to form the radial vein, the ulnar vein, and the median antebrachial vein. The radial vein and the ulnar vein parallel the bones of the forearm and join together at the antebrachium to form the brachial vein , a deep vein that flows into the axillary vein in the brachium.

The median antebrachial vein parallels the ulnar vein, is more medial in location, and joins the basilic vein in the forearm. As the basilic vein reaches the antecubital region, it gives off a branch called the median cubital vein that crosses at an angle to join the cephalic vein. The median cubital vein is the most common site for drawing venous blood in humans. The basilic vein continues through the arm medially and superficially to the axillary vein.

The cephalic vein begins in the antebrachium and drains blood from the superficial surface of the arm into the axillary vein. It is extremely superficial and easily seen along the surface of the biceps brachii muscle in individuals with good muscle tone and in those without excessive subcutaneous adipose tissue in the arms.

The subscapular vein drains blood from the subscapular region and joins the cephalic vein to form the axillary vein . As it passes through the body wall and enters the thorax, the axillary vein becomes the subclavian vein.

Many of the larger veins of the thoracic and abdominal region and upper limb are further represented in the flow chart in Figure 20.39 . Table 20.14 summarizes the veins of the upper limbs.

The Inferior Vena Cava

Other than the small amount of blood drained by the azygos and hemiazygos veins, most of the blood inferior to the diaphragm drains into the inferior vena cava before it is returned to the heart (see Figure 20.36 ). Lying just beneath the parietal peritoneum in the abdominal cavity, the inferior vena cava parallels the abdominal aorta, where it can receive blood from abdominal veins. The lumbar portions of the abdominal wall and spinal cord are drained by a series of lumbar veins , usually four on each side. The ascending lumbar veins drain into either the azygos vein on the right or the hemiazygos vein on the left, and return to the superior vena cava. The remaining lumbar veins drain directly into the inferior vena cava.

Blood supply from the kidneys flows into each renal vein , normally the largest veins entering the inferior vena cava. A number of other, smaller veins empty into the left renal vein. Each adrenal vein drains the adrenal or suprarenal glands located immediately superior to the kidneys. The right adrenal vein enters the inferior vena cava directly, whereas the left adrenal vein enters the left renal vein.

From the male reproductive organs, each testicular vein flows from the scrotum, forming a portion of the spermatic cord. Each ovarian vein drains an ovary in females. Each of these veins is generically called a gonadal vein . The right gonadal vein empties directly into the inferior vena cava, and the left gonadal vein empties into the left renal vein.

Each side of the diaphragm drains into a phrenic vein ; the right phrenic vein empties directly into the inferior vena cava, whereas the left phrenic vein empties into the left renal vein. Blood supply from the liver drains into each hepatic vein and directly into the inferior vena cava. Since the inferior vena cava lies primarily to the right of the vertebral column and aorta, the left renal vein is longer, as are the left phrenic, adrenal, and gonadal veins. The longer length of the left renal vein makes the left kidney the primary target of surgeons removing this organ for donation. Figure 20.40 provides a flow chart of the veins flowing into the inferior vena cava. Table 20.15 summarizes the major veins of the abdominal region.

Veins Draining the Lower Limbs

The superior surface of the foot drains into the digital veins, and the inferior surface drains into the plantar veins , which flow into a complex series of anastomoses in the feet and ankles, including the dorsal venous arch and the plantar venous arch ( Figure 20.41 ). From the dorsal venous arch, blood supply drains into the anterior and posterior tibial veins. The anterior tibial vein drains the area near the tibialis anterior muscle and combines with the posterior tibial vein and the fibular vein to form the popliteal vein. The posterior tibial vein drains the posterior surface of the tibia and joins the popliteal vein. The fibular vein drains the muscles and integument in proximity to the fibula and also joins the popliteal vein. The small saphenous vein located on the lateral surface of the leg drains blood from the superficial regions of the lower leg and foot, and flows into to the popliteal vein . As the popliteal vein passes behind the knee in the popliteal region, it becomes the femoral vein. It is palpable in patients without excessive adipose tissue.

Close to the body wall, the great saphenous vein, the deep femoral vein, and the femoral circumflex vein drain into the femoral vein. The great saphenous vein is a prominent surface vessel located on the medial surface of the leg and thigh that collects blood from the superficial portions of these areas. The deep femoral vein , as the name suggests, drains blood from the deeper portions of the thigh. The femoral circumflex vein forms a loop around the femur just inferior to the trochanters and drains blood from the areas in proximity to the head and neck of the femur.

As the femoral vein penetrates the body wall from the femoral portion of the upper limb, it becomes the external iliac vein , a large vein that drains blood from the leg to the common iliac vein. The pelvic organs and integument drain into the internal iliac vein , which forms from several smaller veins in the region, including the umbilical veins that run on either side of the bladder. The external and internal iliac veins combine near the inferior portion of the sacroiliac joint to form the common iliac vein. In addition to blood supply from the external and internal iliac veins, the middle sacral vein drains the sacral region into the common iliac vein . Similar to the common iliac arteries, the common iliac veins come together at the level of L5 to form the inferior vena cava.

Figure 20.42 is a flow chart of veins flowing into the lower limb. Table 20.16 summarizes the major veins of the lower limbs.

Hepatic Portal System

The liver is a complex biochemical processing plant. It packages nutrients absorbed by the digestive system; produces plasma proteins, clotting factors, and bile; and disposes of worn-out cell components and waste products. Instead of entering the circulation directly, absorbed nutrients and certain wastes (for example, materials produced by the spleen) travel to the liver for processing. They do so via the hepatic portal system ( Figure 20.43 ). Portal systems begin and end in capillaries. In this case, the initial capillaries from the stomach, small intestine, large intestine, and spleen lead to the hepatic portal vein and end in specialized capillaries within the liver, the hepatic sinusoids. You saw the only other portal system with the hypothalamic-hypophyseal portal vessel in the endocrine chapter.

The hepatic portal system consists of the hepatic portal vein and the veins that drain into it. The hepatic portal vein itself is relatively short, beginning at the level of L2 with the confluence of the superior mesenteric and splenic veins. It also receives branches from the inferior mesenteric vein, plus the splenic veins and all their tributaries. The superior mesenteric vein receives blood from the small intestine, two-thirds of the large intestine, and the stomach. The inferior mesenteric vein drains the distal third of the large intestine, including the descending colon, the sigmoid colon, and the rectum. The splenic vein is formed from branches from the spleen, pancreas, and portions of the stomach, and the inferior mesenteric vein. After its formation, the hepatic portal vein also receives branches from the gastric veins of the stomach and cystic veins from the gall bladder. The hepatic portal vein delivers materials from these digestive and circulatory organs directly to the liver for processing.

Because of the hepatic portal system, the liver receives its blood supply from two different sources: from normal systemic circulation via the hepatic artery and from the hepatic portal vein. The liver processes the blood from the portal system to remove certain wastes and excess nutrients, which are stored for later use. This processed blood, as well as the systemic blood that came from the hepatic artery, exits the liver via the right, left, and middle hepatic veins, and flows into the inferior vena cava. Overall systemic blood composition remains relatively stable, since the liver is able to metabolize the absorbed digestive components.

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• Authors: J. Gordon Betts, Kelly A. Young, James A. Wise, Eddie Johnson, Brandon Poe, Dean H. Kruse, Oksana Korol, Jody E. Johnson, Mark Womble, Peter DeSaix
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The 2nd International Seminar on Science Education (ISSE), Graduate School-Yogyakarta State University

Dwitri Pilendia

Abstract—Some of skills required in the 21st century are critical thinking, Information Communication Technology (ICT) literacy, and socio cultural interaction. Physics learning should be directed to develop these aspects. This paper describes a preliminary validation study of developing an interactive multimedia module that covering the 21st century skill. The method of this research is Research & Development. The subjects of this developing study were 10th grade student of senior high school in Padang, Indonesia.The data presented are the result of the define, designe, and valiadtion phase of pruduct. Based on questionnaire analysis show that students interested in learning physics using ICT reached 76.7%, but the fact that teacher have not been using teaching material based on ICT, Problem Based Learning (PBL) model is not maximized, the students' critical thinking skills are only 69.3% and the learning outcomes of students yet fully achieve the minimum completeness criteria. Based on the analysis of questionnaires and observation, generally seen that not maximal adherence to the learning process that impact on the learning outcomes of students. One way that can resolve these problems is using interactive multimedia modules in PBL model aided games. The validation of design show that interactive multimedia modules is valid.

Imam Farisi

The purpose of the study is to describe student’s performance in tutorial online (tuton) of Social Studies through developing the 5Es—Engage, Explore, Explain, Elaborate, and Evaluate—Learning Cycle Model (the 5Es-LCM). The study conducted at UT-Online portal uses the Research and Development (R&D) method. The research subjects consisted of 21 UT’s students from 16 UT’s Regional Center (UPBJJ) in Indonesia. Data collected use the documentation and validation techniques, and analyzed use the descriptive-percentage techniques. Qualitatively, student’s performance is ‘low’, viewed from students’ activities/participations in initiation, discussion, and ask-questions forums. Qualitatively, however, the quality of their performance is 'good', viewed from processes and contents of discussion and ask-questions; timeliness in the completion and scores of assignments; and competencies achieved. Some factors cause the low of students’ performance in the tuton are the limited time for access, and technical factors.

International Journal Innovation, Creativity and Change

Citra Ayu Dewi , Martini Tini , Zulkarnain Gazali

The purpose of this study is to develop ethnoscience based acid-base modules to improve student's scientific literacy ability. This study is developmental research using the ADDIE design model limited to the evaluation stage. The draft module was validated by two material experts and one media expert using a validated questionnaire. The module effectiveness test uses a pre-experimental model with one pretest-posttest group. The research design for the number of research subjects factored for as many as 30 students. Module effectiveness is analysed from graduation, n-gain scores, and t-test results of the pre-test and post-test. The results of content and design validations was 80% and 87% with valid criteria without revision, an n-gain score of 0.4 with medium category, and the t-test showed that there were significant differences between pre-test and post-test. Thus, it can be concluded that the ethnoscience based acid-base module can effectively improve students' scientific literacy ability in basic chemistry learning.

The 8th International Conference on Educational Research and Innovation (ICERI)

reflina sinaga

Jurnal Inovasi Pendidikan IPA

Sulton Nawawi

This research aimed to compile a product development, knowing the feasibility and knowing the effectiveness of challenge-based learning (CBL) modules in an environmental material to empower the critical thinking ability. The research was a research & development model of Borg & Gall. Validation the product was done by material expert, expert of development and design module, expert of device and evaluation of learning , a linguist and practitioner of learning of Biology. Subject of the research was a student of grade X MIA Islamic State Senior High School Karanganyar. This research results are: (1) module in the form of product module for teachers and students CBL based on environmental material was developed based on CBL syntax and indicators of Fascione's critical thinking that visualized in the objective, material, activities , and evaluation items; (2) appropriateness of module for teachers and student based on CBL environment material according to the validation results of qualified as good until very good; (3) Modules based CBL environmental material is effective to improve the ability of student critical thinking.

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7.8.10: Critical Thinking Questions

• Last updated
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• Page ID 98269

Describe a closed circulatory system.

Describe systemic circulation.

Describe the cause of different blood type groups.

List some of the functions of blood in the body.

How does the lymphatic system work with blood flow?

Describe the cardiac cycle.

What happens in capillaries?

How does blood pressure change during heavy exercise?

Evaluating critical thinking in clinical concept maps: a pilot study

Affiliation.

• 1 University of New Brunswick, Saint John, Canada. [email protected]
• PMID: 17140395
• DOI: 10.2202/1548-923X.1314

Today, the complexities in the health care system are challenging nurses to be skillful and knowledgeable critical thinkers and decision makers. To adequately prepare future nurses to meet the challenges, nurse educators must nurture and facilitate critical thinking. One strategy believed to promote critical thinking in nursing education is concept maps. The purpose of this pilot study was to determine the level of critical thinking in the clinical concept maps developed by second year baccalaureate nursing students. Students enrolled in a five-week clinical practicum course were asked to submit their final concept map and participate in a focus group. The data for the study included eighteen concept maps, 1 student focus group and 1 instructor focus group. The Holistic Critical Thinking Scoring Rubric (Facione & Facione, 1994) was used to measure levels of critical thinking, and content analysis was used to analyze focus group data. Results from this study indicated that developing concept maps in the clinical setting fostered critical thinking and improved clinical preparedness.

Publication types

• Evaluation Study
• Concept Formation*
• Critical Care*
• Decision Making
• Education, Nursing*
• Pilot Projects
• Problem Solving

Mind Map Gallery Circulatory System Mind Map

Circulatory System Mind Map

The circulatory system is made up of blood vessels that carry blood away from and towards the heart.

• Recommended to you

Circulatory-System-Concept-Map

Transport oxygen, nutrients, and othersubstances throughout the body

Pump blood through the circulatory system.

It's divided into two ventricles and two atria.

Body's transportation system.

It's about 90 percent water and 10 percent othersubstances.

Red Blood Celles

Transport oxygen.

White Blood Cells

Guard against infection, fight parasites, andattack bacteria

Is in charge of blood clotting.

Blood Vessels

Carry blood from the heart to the tissues of thebody.

It returns the blood from the capillaries to theheart.

Capillaries

Allow oxygen and nutrients to diffuse from theblood into tissues, and carbon dioxide

Heart Disease

When the coronary arteries obstruct, and heartmuscle dies.

The suden death of brain cells when their bloodsupply is interrupted.

High Blood Pressure

When the blood pressure is 140/90 or higher.

Circulation

Pulmunary Circulation

Heart pumps oxygenpoor blood from the heartto the lungs.

Systemic Circulation

Heart pumps oxygenrich blood to the rest of thebody.