I know, we just finished the muscle and bones.....and now I'm asking you to learn even more. So, empty your brain and get ready for more. Today we will tackle heart anatomy and physiology.
I'm just finishing up the booklets for this next section and will have them ready Monday. For the heart class (Monday), please download or print the lecture slides from here, watch the videos, and answer the preview questions.
12.1. The heart is a muscular organ with chambers that are filled with blood. When it contracts, it pumps that blood into attached tubes, which then distribute it throughout the body. The heart is about the size of your fist and lies behind the chest wall, slightly to the left. Most big tubes (called ‘the great vessels’) plug into it from the top, suspending the heart downward. What organs lie on each side of the heart?
12.2. When the heart pumps (contracts), it creates friction. Friction can cause tissue damage. To protect against that, the heart is suspended in a fluid filled bag (‘pericardial sac’). The ‘serous fluid’ itself is created by the body and kept in an enclosed space, so that it doesn’t leak out. Visualize an air-filled balloon, make a fist (about heart size), and push it into it; the balloon symbolizes the ‘serous’ membrane, and the air space between is filled with serous fluid in the body. The serous membrane around the heart is called pericardium. Peri- means around, -cardium refers to the heart. The part of the serous membranes covering the heart is referred to as the visceral pericardium. What is the other part named, the one on the outside?
12.3. Beneath all those membranes lies the heart muscle itself. What term do we us to describe it?
12.4. You might have heard of arteries and veins. Those are the pipes attached to the heart. The ones leading away from the heart have to be strong walled and withstand the pressure forces of the blood being pumped out of the heart. The other ones don’t have to worry about that, they rather guide the blood back into the heart as it returns from its journey through the body. Which type are the arteries? Which the veins?
12.5. Having tubes attached to the heart that guide the blood away from it and then bring it back to it, makes this a closed system. The heart actually pumps blood into 2 of those systems; one goes to the lungs to fill the red blood cells up with oxygen, and the other delivers that oxygen to all body cells, so that they can help make the body ATP (energy). What do we call the two cardiac circuits?
12.6. On the inside of the heart are chambers (hollow spaces) filled with blood. When the heart contracts, the squeezing propels the blood forward. There are four chambers altogether, two for each circuit. The ones on the right pump the blood to the lungs, the ones on the left to the body. Each side has a smaller receiving chamber on top and an ejection chamber on the bottom of the heart. What are they called respectively?
12.7. When the heart contracts, the body needs to make sure the blood gets pumped forward and doesn’t get pushed backwards; valves make sure of that. One set of them guard between the receiving and ejecting chambers. They are constructed quite exquisitely. Flaps cover the opening between the chambers when the heart contracts. What are those set of valves called?
12.8. Another set of valves cover the exit of the ejection chamber. When the blood gets pumped out of the heart into the ’great vessels’, they prevent the blood from falling back into the heart. What are those valves called?
12.9. Understanding the pathway through the heart is important. Blood enters on both sides (right and left) into receiving chambers on top. From there it passes by one set of valves (that are open at this point) into the ejection chambers on the bottom of the heart. When the heart contracts, the first set of valves close to prevent backflow and the second set gets pushed open as the blood forcefully rushes into the pipes leading away from the heart. Can you list the parts of the pulmonary and systemic circuit?
12.10. The heart cannot use the blood it pumps to feed its own muscle. It needs to divert oxygenated blood from the bottom of the aorta. What are the two main ‘coronary’ arteries called?
12.11. As a pump, the heart has to contract rhythmically. Since heart muscle cells don’t contract on their own, they need to be stimulated by a nerve impulse each time the heart pumps. As a clever muscle, the heart built its own ‘pace-maker’ right into itself by the right atrium. From there, it activates the muscle cells, first the ones by the atria. The impulse then gets intensified and spreads throughout the walls of the ventricles making the cells contract in unison all at once (called ‘functional syncytium’). Can you name the different parts of this brilliant conducting system?
12.12. In order to understand how the heart’s electrical impulse system works, we can measure the light electrical current that stimulates the muscle cells. An electro-cardio-gram (ECG) is a tracing of that. The deviations from the horizontal line mean electrical activity. What does the QRS-complex indicate?
12.13. The heart muscle contracts rhythmically to pump blood. After a contraction, it has to relax to fill up with blood again. What terms do we use to describe these two states of this bi-phasic cycle?
12.14. We can listen to the heart. It actually makes two distinct sounds: LUB and DUB. Those sounds are produced when the heart valves close. Which valves make which sound?
12.15. The cardiac cycle describes the events of one full contraction of the heart. It mainly describes what chamber is filling and which one is contracting. Please list the events of the cardiac cycle.
12.16. And lastly for this chapter, we have to figure out how much blood the heart pumps. The cardiac output measures the volume ejected by the heart in one minute. What are the two factors that determine how much that is?
Please send me the answers you came up with to those questions beforethe class meets to [email protected] Thank you.
Here is a video describing the anatomical terms: