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Circulatory story. Worksheet about the circulatory system that involves how blood moves in and out of the heart...

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NATIONAL CENTER FOR CASE STUDY TEACHING IN SCIENCE

Cardiac Blood Flow: A Circulatory Story by Hollie L. Leavitt Department of Biology College of Western Idaho, Nampa, ID

Part I – Heart Anatomy Josie was a 43-year-old former college athlete who enjoyed staying at home with her three young children. Even though she had always tried to maintain an active healthy lifestyle, over the past several months Josie had felt increasingly tired to the point that she sometimes was unable to do normal household activities like cooking dinner or folding laundry. Initially Josie chalked up her exhaustion to “just being 40-something,” but following an episode where she awoke in the middle of the night feeling very short of breath, she decided to see her primary care physician. Upon listening to her heart with a stethoscope, her doctor referred her to a cardiologist. Three weeks later, Josie was sitting nervously in the cardiologist’s exam room waiting for him to enter. This was her second appointment with Dr. Adams, and the plan was to discuss the results from her physical examination, labs, and echocardiogram. She heard footsteps coming down the hall, a rustling of papers at the door, and then a quick knock before Dr. Adams poked his head in. Josie and her doctor exchanged pleasantries before Dr. Adams became more serious and took a seat in his exam chair across from her. “Josie,” he began, “based on the results of the tests we ran last week and your physical exam, I am diagnosing you with congestive heart failure.” Josie’s head was spinning. That sounded serious—potentially life-threateningly serious! Her mind raced. I’m too young for this... I’ve always lived a healthy lifestyle and expected a different result... This isn’t fair! What will my kids do if I die?” Dr. Adams continued. “I recognize this is a shock. I want you to know that as your doctor, I’m here to help you develop the best possible plan to ensure the greatest quality of life despite this diagnosis. What questions do you have right now that I can help with?” “Uh…what is congestive heart failure?” Josie stammered. “Am I going to die?” “Let me explain to you a little about the anatomy of the heart and its function to help you better understand this disease,” was Dr. Adams gentle reply.

Questions 1. Label the following on Figure 1 (next page): right atrium, left atrium, right ventricle, left ventricle, bicuspid valve, tricuspid valve, aortic semilunar valve, pulmonary semilunar valve. 2. Label the blood vessels on the diagram: inferior vena cava, superior vena cava, pulmonary trunk, pulmonary arteries, pulmonary veins, and aorta. 3. List the order that blood passes through each of the structures you’ve labelled, beginning with the inferior and superior vena cava. Inferior/superior vena cava, right atrium, tricuspid valve, right ventricle, pulmonary arteries, lungs, pulmonary veins, left atrium, mitral valve, left ventricle, aortic valve, aorta Case copyright held by the National Center for Case Study Teaching in Science, University at Buffalo, State University of New York. Originally published March 2, 2020. Please see our usage guidelines, which outline our policy concerning permissible reproduction of this work. Licensed image in titleblock © Diunos | Dreamstime.com, id 42396583.

4. Use markers, crayons, or colored pencils to color the chambers of the heart and blood vessels either red or blue, depending on how highly oxygenated the blood contained within them is. Highly oxygenated blood is bright red, so color areas containing highly oxygenated blood red and those containing blood with lower oxygen levels blue. 5. Explain why there is a difference in oxygen content of the blood on the two sides of the heart. There is a dierence in oxygen content on the two sides of the heart because they pump blood to dierent structures. On the right side deoxygenated blood is more concentrated because the deoxygenated blood is sent to the lungs to become oxygenated and then it is returned onto the left side. On the left side, oxygenated blood is sent to all the other structures excluding the lungs and then the organs/tissues/muscles use that oxygenated blood and returns the deoxygenated blood back to the right side.

Figure 1. Longitudinal section of a human heart. Credit: pd, . “Cardiac Blood Flow” by Hollie L. Leavitt

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Part II – Circuits of Blood Flow Dr. Adams continued with his teaching “The right side of the heart pumps deoxygenated blood to the lungs, while the left side of the heart pumps highly oxygenated blood that has just returned from the lungs to all the tissues of the body. With congestive heart failure, your heart has weakened, and it doesn’t pump as effectively. Less blood and therefore less oxygen gets to your tissues and organs. Josie, this is why you’ve felt so tired and also short of breath.”

Questions 1. In your own words, define pulmonary circuit and systemic circuit. Pulmonary circuit is when deoxygenated blood is pumped out of the right side of the heart to the lung to get oxygenated and then is returned to the left side. Systemic circuit is when oxygenated blood from the left side is pumped to the all the tissues of the body to be used and then returns as deoxygenated blood to the right side.

2. Based on where they must pump blood to, which side of the heart do you think must pump harder, right or left? Explain your answer, and use anatomical evidence from the heart to support your argument. The left side must pump harder because it has to pump to all the tissues in the body while the right side just pumps the lungs

3. Based on what you’ve learned so far, which side of the heart do you think more commonly weakens faster and fails first? Explain your answer. The left side probably weakens faster because it pumps harder and does more work compared to the right side.

Part III – Blood Flow in Heart Failure “I took a human anatomy class in college and remember learning about the systemic and pulmonary circuits,” Josie responded. “I always found them kind of confusing because the textbooks would show them as a figure eight with the heart at the center, and with all the valves inside and the vessels coming off of the heart. I got confused about where the blood was moving.” “I’ve got a picture that I think may simplify that for you quite a bit and help you to understand what is going on with blood flow in your body. Take a look at this,” Dr. Adams said as he handed Josie a paper with a diagram on it (Figure 2). “Let me explain this to you,” he continued. “I think it will Figure 2. Simplified representation of pulmonary and systemic circuits. simplify the circuits and help you to understand how blood is moving through the body, and why there is a problem if one or both sides of the heart fail. This leaves out all of the additional anatomy so that you can just focus on the left side of the heart being a pump that moves blood from the pulmonary circuit to the systemic circuit, and the right side of the heart a pump that moves blood from the systemic circuit to the pulmonary. The arrows in this diagram can help you remember in which direction the blood is moving.”

“Cardiac Blood Flow” by Hollie L. Leavitt

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Questions 1. If the left side of the heart fails, where in the circulation would blood back up? What about the right side? If the left side of the heart fails blood would be backed up in the pulmonary veins. If the right side was backed up blo would be backed up in the superior/inferior vena cavas. pulmonary circuit 2. Fill-in-the-blanks: Blood flow into the ___________________ (pulmonary circuit/systemic circuit) would

_____________ (increase/decrease) if the left side of the heart fails. Blood flow into thesystemic ____________ decrease circuit (pulmonary decrease circuit/systemic circuit) would _________________ (increase/decrease) if the right side of the heart fails.

3. Describe what would happen to pressure in the blood vessels where blood is backing up and pooling due to failure of the heart. The pressure would increase due to the built up pressure of the blood backing up and pooling in the veins.

4. Capillaries are by far the most common type of blood vessel in the body, and most capillaries are very porous— they leak fluid. Blood is mostly fluid. The swelling caused by fluids leaking from the blood into tissues is known as edema. Predict where in the body you would see edema related to left-sided heart failure, and where you would see edema related to right-sided heart failure. Be sure to explain your answers. In right-sided heart failure you would see swelling in the lungs because of all the built up pressure and fluid. in leftsided failure you would see swelling in all the tissues around the body because of all the backed up blood.

5. Describe why heart failure is so often referred to as “congestive” heart failure. Heart failure is caused by fluid and blood building up in the veins and causes the blood to be backed up. This is called congestion.

6. If the left side of the heart were failing, how would this change the pressure that the right side of the heart needed to generate to continue moving blood into the pulmonary circuit? On the right side of the heart the pulmonary arteries would be backed up and cause a build up of pressure making it harder to the right side to pump to the lungs eciently

7. Left-sided heart failure is the primary cause of right-sided heart failure. Explain why this might be. When the left side fails, all the blood gets backed up in the pulmonary veins which connect to the right side of the heart so all the built up blood and pressure causes the right side to fail.

8. Feeling short of breath was one of the symptoms that led Josie to see her doctor originally. What do you think happens to oxygen levels in the blood when the left side of the heart fails? Explain your answer and discuss why Josie has been feeling short of breath. Oxygen levels decrease when the left side fails because the left side is not able to pump the oxygenated blood to all the surrounding tissues.

“Cardiac Blood Flow” by Hollie L. Leavitt

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Part IV – Blood Flow and Valve Issues “This all makes sense,” Josie said, “but what I don’t understand and what I’m really frustrated about is I’ve always been active! Until I became too exhausted to do anything I worked out regularly. I eat a healthy diet. I don’t smoke! I don’t have any of the risk factors that would predispose me to this disease, so why do I have it? Why me?” “Josie, you have a narrowed bicuspid valve that has caused the problem. It’s possible this was a congenital heart defect that was never noticed and didn’t cause a lot of problems until your heart was permanently damaged. It’s also possible that damage was caused to the valve by an infection like rheumatic fever. Unfortunately, congestive heart failure isn’t something that can always be prevented.”

Questions 1. How would a stenotic bicuspid valve affect the movement of blood from the left atrium to the left ventricle? Blood would not be able to pass through easily and as eciently so the movement would be slow and minimal.

2. Which of the four chambers of the heart would have its workload increased the most by a stenotic bicuspid valve? Explain your answer. The left atrium would have its workload increased because it will be harder to pump to the left ventricle.

3. Suppose it were the pulmonary semilunar valve that were stenotic. Which of the four chambers of the heart would have its workload increased the most and why? The right ventricle would have to work harder to pump blood through the narrow valve.

4. Describe how a stenotic valve increases the risk of heart failure. When the valve opening becomes narrowed, it limits the flow of blood out of the ventricles or atria. This will cause the chambers to overwork and not be able to pump blood eciently which can eventually lead to heart failure.

5. In Josie’s case congestive heart failure was caused by a stenotic bicuspid valve. However, other valve abnormalities can also cause heart failure. Define valve regurgitation and explain how it could also lead to a failing heart. Valve regurgitation is when the valves do not close properly. If a valve doesn't close properly it can cause blood to flow backwards and go where it's not supposed to leading the heart failure.

“Cardiac Blood Flow” by Hollie L. Leavitt

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