It s a Matter of the Heart Investigating the Circulatory System

Transcription

1 It s a Matter of the Heart Investigating the Circulatory System OBJECTIVE Students will investigate the structure and function of the heart in relation to the circulatory system. Students will identify the role that the heart plays and the relationship between the circulatory system and other body systems. LEVEL Middle Grades Life Science NATIONAL STANDARDS UCP. 1, UCP. 5, C.5, A.1 CONNECTIONS TO AP AP Biology: III. Organisms and Populations B. Structure and Function of Plants and Animals TIME FRAME 50 minutes MATERIALS (For a class of 28 working in groups of 2) 14 preserved sheep hearts 14 dissection scissors 14 dissection scalpels 70 dissection pins (5 per group) 14 dissection blunt-end probes/seekers protective gloves 14 forceps 14 dissection trays 14 red colored pencils 14 blue colored pencils model(s) of human heart T E A C H E R P A G E S TEACHER NOTES This lesson is designed to give students an understanding of the function of the circulatory system by investigating the structure of the heart. Students will identify both external and internal structures that are involved in the function of the heart. Students will also identify relationships between the heart and the other systems of the body. This activity should be used to accompany a unit on body systems and should be taught after students have an understanding of body organization (cells-tissues-organs-organs systems). Students should also have some knowledge of the respiratory system and a basic understanding of the purpose and types of muscle tissue. Preserved sheep hearts need to be purchased in advance of this lab. It should be noted that some students will be opposed to working with preserved specimens. Check with your administration to identify the proper protocol for you, the teacher, in the event that a student does not want to participate. Alternate activity suggestions include: Copyright 2010 Laying the Foundation, Inc. Dallas, TX. All rights reserved. Visit: 1

2 Having the student work from their book to study the heart structure and function. The data and observations, analysis and conclusion included in this lab can still be answered if working from a book. A computer simulation could be used, however most must be purchased. This would also require student access to computers and software. Dissection Notes/Setup: Note: This dissection should be a teacher-led, whole group activity. Although the procedures are listed, it will be more effective to make sure each procedure is done by each student with the teacher guiding the cuts and the probing. To assist you in the process, it would be best to do the first cut before handing out the hearts your first cut will be into the vena cava and students can then cut from there by following your further instruction and the procedure. It is also advised that a pre-cut heart be available for demonstration/viewing purposes. You may also choose to pre-cut all hearts and keep them together with a rubber band. As you follow the procedure, you can still allow them to probe, explore, just advise that cuts were already made. Label the dissection trays to indicate the correct orientation of the heart so that students understand what they are looking at. The student will be observing in anatomical position so they will see the left side of the heart on their right side and vice-versa. Label the tray as follows before giving trays to students: Top T E A C H E R P A G E S Right Left Bottom Figure 1 Copyright 2010 Laying the Foundation, Inc. Dallas, TX. All rights reserved. Visit: 2

3 Also, make sure you rinse the sheep hearts before placing them in the trays. The heart dissection will provide students an insight to the valve location, space location as well as exit/entry points for blood into and out of the heart. To correctly orient the preserved heart make sure that the apex (rounded bottom area) of the heart is pointed towards the bottom of the dissection tray and the anterior (front) portion of the heart is facing up. Note: You can hold the heart in your hand and locate the darker flaps of tissue at the top of the heart you can also give the heart a gentle squeeze the thicker, more muscular side of the heart is the left side. To begin dissection, you should be looking at the anterior (front) of the heart, A good clue to indicate that you are looking at the anterior side of the heart is the darker muscle tissue (see Figure 1) the right ventricle is a smaller patch of dark muscle tissue while the left ventricle is a larger dark patch of muscle. Also, the coronary vessel will divide the heart for you, externally (see Figure 1). The apex will point slightly to the left if you are viewing the heart in anatomical position. Another indicator is the auricles (darker patches of tissue at the top of the heart) are both visible and sitting nicely atop the heart. Vessels will be more visible on the posterior (back ) region of the heart. External structures of importance are the aorta and the apex although diagrams in this activity will include vena cava, most preserved specimens do not have a clear visualization of these (we ll locate them when we get to the inside of the heart). The internal structures of importance are the right and left atria (plural) the right atrium (singular) houses blood entering the heart from the vena cava, while the left atrium is the space that house blood returning to the heart from the lungs. Other structures to note are the right and left ventricles. The right ventricle is the space that houses blood before it leaves the heart to go to the lungs, while the left ventricle houses blood that is leaving the heart through the aorta. The valves that control the heart are found (and will not be easily identified, so note that to the students) between the right atrium/ventricle, between the left atrium/ventricle, and also found in the aorta and pulmonary artery. The function of valves is to prevent the backflow of blood. The tricuspid valve, found between the right atrium and right ventricle, prevents the mixing of blood in the two chambers. The valve found between the left atrium and left ventricle is called the bicuspid, or mitral valve, which prevents mixing of blood in those two chambers. T E A C H E R P A G E S Blood returning from the body enters the right side of the heart through the vena cava. The blood is emptied into the right atrium, and then moves through a valve into the right ventricle. Blood found on the right side of the heart is lacking oxygen, or de-oxygenated. This is because it is returning from the body and has dropped off the oxygen to the cells. At the same time, it has picked up carbon dioxide (a gas that our body does not use, waste). It is returning to the heart to pick up more oxygen. When the blood leaves the right ventricle, it travels through pulmonary arteries to the lungs to pick up oxygen and drop off carbon dioxide. A valve in the pulmonary artery prevents backflow of blood once it is oxygenated. From the lungs, it returns through the pulmonary veins, enters the left side of the heart. It is emptied into the left atrium and moves through a valve into the left ventricle. From here, it is pumped out of the heart through the aorta. The aorta contains a valve that helps prevent the oxygenated blood from flowing back into the heart. The left side of the heart is also much more muscular so that it is able to pump the blood to the body. Copyright 2010 Laying the Foundation, Inc. Dallas, TX. All rights reserved. Visit: 3

4 REFERENCES A really nice photo of the sheep heart and what students should see when it is opened up: And another: Photo of sheep heart, just out of package (external anatomy) Photo of the first cut (right side of heart atrium and ventricle labeled) Photo of the second cut (left side of heart atrium and ventricle labeled) DATA AND OBSERVATIONS Vena Cava Structure Function Location Right Atrium Right Ventricle Pulmonary Artery Pulmonary Vein Left Atrium Left Ventricle Aorta Return blood from the body to the heart chamber that holds blood entering the heart from the body Chamber that holds blood before it moves into the lungs Carries blood away from the heart to the lungs Carries blood back to the heart from the lungs Chamber that holds blood when it returns from the lungs Chamber that holds blood before it is pumped out of the heart to the body Carries blood from the heart back to the body Right side of the heart near the right atrium Right side of the heart Right side of the heart Between the right ventricle and the lungs Between the left atrium and the lungs Left side of the heart Left side of the heart Left ventricle and moving upwards to the top of the heart Blood (Oxygenated or De-oxygenated) De-oxygenated De-oxygenated De-oxygenated De-oxygenated Oxygenated Oxygenated Oxygenated oxygenated T E A C H E R P A G E S Copyright 2010 Laying the Foundation, Inc. Dallas, TX. All rights reserved. Visit: 4

5 ANALYSIS Label the following diagram of the human heart. Using red and blue colored pencils, trace the flow of blood through the heart, beginning with the vena cava and ending with the aorta. Red will be used to indicate blood that is oxygenated and blue will be used to indicate blood that is de-oxygenated. 1. What is the purpose of heart valves? To prevent the backflow of blood 2. What is the purpose of blood traveling to the lungs? T E A C H E R P A G E S To pick up oxygen and drop of carbon dioxide 3. Can an artery carry de-oxygenated blood? If yes, give a specific example. Yes, the pulmonary artery carries de-oxygenated blood away from the heart to the lungs. CONCLUSION QUESTIONS 1. What is the primary purpose of the circulatory system? What is the role of the heart in the circulatory system? To deliver oxygenated blood to cells. It also serves to return de-oxygenated blood to the heart so that it can become oxygenated. The heart serves as the pump in this system. Copyright 2010 Laying the Foundation, Inc. Dallas, TX. All rights reserved. Visit: 5

6 2. Compare the sheep heart structure to human heart structure; include among other comparisons how many chambers each have? (You may use your notes and text as a reference.) Both have a right and left side Both have vena cava Both have pulmonary veins/arteries Both have valves other answers, as appropriate The human heart has 4 chambers, the sheep heart has 4 chambers. 3. Why is it important for the heart to be composed of muscle tissue? What type of muscle is the human heart (voluntary or involuntary)? The heart must pump blood to the body muscle tissue aids in movement Involuntary muscle tissue 4. Describe the relationship between the circulatory system and the respiratory system. The respiratory system exchanges gases oxygen and carbon dioxide. The circulatory system picks up oxygen in the lungs and carries the oxygen to the cells of the body and brings the carbon dioxide (waste) back to the lungs to be exhaled. 5. Why do cells need oxygen? T E A C H E R P A G E S To create energy. Energy is created through a process known as cellular respiration. In this process, oxygen diffuses into cells and is used to create ATP, the molecule that cells use for energy. A waste product of cellular respiration is carbon dioxide, which is exhaled during breathing. 6. Imagine that the wall between the right and left ventricle of the heart was removed. Would this affect the function of the human heart? Why or why not? It would affect the function the blood in the right ventricle is de-oxygenated and the blood in the left ventricle is oxygenated. The blood would mix and never become truly oxygenated, therefore shutting down the primary purpose of the circulatory system. Copyright 2010 Laying the Foundation, Inc. Dallas, TX. All rights reserved. Visit: 6

7 7. A person has been diagnosed with mitral valve prolapse, a condition in which the valve that separates the blood in the left side of the heart does not close properly. Based on your knowledge of blood flow in the heart, what problems may this cause in the heart? Would these problems be noticeable to the person? Why or why not? The blood may mix in the atrium and ventricle. The blood may not all be reaching the ventricle to be pumped to the body. Students can argue either way yes, it could matter or no it wouldn t. In either case, they need to back up their answer with what they have learned about blood flow and valve function. In most cases, the person with mitral valve prolapse will exhibit no symptoms however, in severe cases there can be fatigue, shortness of breath, etc. 8. What is the significance of the heart muscle tissue being thicker in the walls of the left side of the heart as opposed to the right side of the heart? The walls are thicker because that is the pumping side of the heart. The blood returning from the lungs goes to this side of the heart to be pumped to the entire body. On the right side, blood is simply returning (or spilling into) the heart. T E A C H E R P A G E S Copyright 2010 Laying the Foundation, Inc. Dallas, TX. All rights reserved. Visit: 7

8 It s a Matter of the Heart Investigating the Circulatory System The heart can be considered one of the body s most important muscles. Muscles can be either voluntary, where the movement is not automatically controlled, or involuntary, where the nervous system automatically controls the movement. The heart has the job of pumping blood to all tissues in the body so that each cell within those tissues has oxygen. In order to do that, blood must circulate through the body. The blood circulating through the body stays within vessels, called arteries, capillaries and veins. This working body system is called the circulatory system. Most body systems work together. The circulatory system works together with the lungs in the respiratory system. Recall that your respiratory system exchanges carbon dioxide when you exhale for oxygen when you inhale. Because your cells require oxygen, they must rely on the respiratory system to supply the circulatory system with that oxygen. At the level of the cell, the oxygen is exchanged for the carbon dioxide, which is not needed by our bodies and is removed as waste. The structure of the heart includes spaces within the heart, called atria and ventricles. These spaces hold blood until it is pumped to other spaces with each heartbeat. In general (but not in all cases), veins carry blood that has lost its oxygen to cells (de-oxygenated) and arteries carry blood that have received new oxygen in the lungs (oxygenated). There are two large veins that carry blood from the body back to the heart, called vena cava. These veins dump blood into the space in the heart called the right atrium. Once in the right atrium, the blood moves into the right ventricle. In both of the spaces, the right atrium and ventricle, the blood lacks oxygen, or is deoxygenated. From the right ventricle, blood moves to the lungs through the pulmonary arteries. In the lungs, blood receives oxygen and releases carbon dioxide through a process called simple diffusion and then moves back into the heart through the pulmonary veins. When blood moves back into the heart it is considered oxygenated and moves into the space called the left atrium. From the left atrium it travels to the left ventricle, which has a thick wall of muscle. The purpose of this thick wall of muscle is to then pump the blood out of the heart, through the aorta and then into the arteries of the body. PURPOSE In this lab, you will identify the structure of the heart and relate the structure to the function of the circulatory system. You will also make comparisons between the sheep heart and the human heart. Copyright 2010 Laying the Foundation, Inc. Dallas, TX. All rights reserved. Visit: 1

9 MATERIALS preserved sheep heart dissection scalpel dissection blunt-end probe/seeker Forceps red colored pencil model of human heart dissection scissor 5 dissection pins gloves dissection tray blue colored pencil Safety Alert You are working with preserved specimens. You should wear appropriate lab aprons, goggles, and gloves. Handle sharp dissecting tools carefully, with blades and sharp ends pointed toward the floor and away from your body. When cutting with blades, cut away from your body. PROCEDURE 1. Obtain a sheep heart and dissection tools from your teacher. 2. Locate the apex of the heart. It should be pointed towards the bottom of your dissection tray. Notice that your tray is labeled, top, bottom, left and right. 3. Next, your teacher will help you identify the left and right sides of the heart. Make sure your heart lies correctly in your dissection tray with the left side facing the side labeled left and the right side facing the side labeled right. Your heart is now in anatomical position. Notice that the left side of the heart is thicker and more muscular. This is because blood is pumped out of the heart and to all parts of the body from that side. 4. Using your blunt-end probe, locate the vessels that open into the right, top-side of the heart. This is the vena cava, the vessel that empties blood from the body into the heart. 5. Your vena cava has already been cut and you can look into the vena cava to see the right atrium. You may also see a valve when looking into the atrium (strings of tissue) this is the triscuspid valve. 6. Using your scissors, continue the cut towards the bottom of the heart. The space below the valve is the right ventricle. 7. Next you will use your blunt-tip probe to locate the pulmonary arteries beginning in the right ventricle. Follow your teacher s instructions on how to use the probe to locate these arteries 8. Next, you will follow your teachers instructions to open the left side of the heart. To open the left atrium, use the blade of the scissors to cut through the outer wall of the left atrium. You will cut towards the apex of the heart. Copyright 2010 Laying the Foundation, Inc. Dallas, TX. All rights reserved. Visit: 2

10 9. You will see another valve separating the left atrium and the left ventricle. This is the bicuspid valve, or mitral valve. 10. Follow your teacher s instructions to use your blunt-tip probe to locate the pulmonary veins beginning in the left atrium, probe into the vessels that bring blood back to the heart from the lungs. 11. Follow your teacher s instructions to use your blunt-tip probe to locate the aorta by inserting it in the left ventricle and probing upward through the vessel the probe should come out at the top of the heart. 12. Using your dissected sheep heart, models of the human heart and your notes/textbook, complete the Data Table in your student answer pages. 13. Complete the analysis and conclusion questions that follow. Copyright 2010 Laying the Foundation, Inc. Dallas, TX. All rights reserved. Visit: 3

11 It s a Matter of the Heart Investigating the Circulatory System DATA AND OBSERVATIONS Data Table: Structure and Function of the Heart Structure Function Location Blood (Oxygenated or De-oxygenated) Vena Cava Right Atrium Right Ventricle Pulmonary Artery Pulmonary Vein Left Atrium Left Ventricle Aorta Copyright 2010 Laying the Foundation, Inc. Dallas, TX. All rights reserved. Visit: 4

12 ANALYSIS Label the following diagram of the human heart. Using red and blue colored pencils, trace the flow of blood through the heart, beginning with the vena cava and ending with the aorta. Red will be used to indicate blood that is oxygenated and blue will be used to indicate blood that is de-oxygenated. 1. What is the purpose of heart valves? 2. What is the purpose of blood traveling to the lungs? 3. Can an artery carry de-oxygenated blood? If yes, give a specific example. Copyright 2010 Laying the Foundation, Inc. Dallas, TX. All rights reserved. Visit: 5

13 CONCLUSION QUESTIONS 1. What is the primary purpose of the circulatory system? What is the role of the heart in the circulatory system? 2. Compare the sheep heart structure to human heart structure; include among other comparisons how many chambers each have? (You may use your notes and text as a reference.) 3. Why is it important for the heart to be composed of muscle tissue? What type of muscle is the human heart (voluntary or involuntary)? 4. Describe the relationship between the circulatory system and the respiratory system. 5. Why do cells need oxygen? 6. Imagine that the wall between the right and left ventricle of the heart was removed. Would this affect the function of the human heart? Why or why not? Copyright 2010 Laying the Foundation, Inc. Dallas, TX. All rights reserved. Visit: 6

14 7. A person has been diagnosed with mitral valve prolapse, a condition in which the valve that separates the blood in the left side of the heart does not close properly. Based on your knowledge of blood flow in the heart, what problems may this cause in the heart? Would these problems be noticeable to the person? Why or why not? 8. What is the significance of the heart muscle tissue being thicker in the walls of the left side of the heart as opposed to the right side of the heart? Copyright 2010 Laying the Foundation, Inc. Dallas, TX. All rights reserved. Visit: 7