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The Heart and the Immune System

The Heart Slide 1 The Heart So far we have looked at two parts of the circulatory system, the blood and the blood vessels. Now let’s look at the third component of the circulatory system, the heart. The heart serves as a pump to keep the blood moving through the vessels. Slide 2 Parts of the heart The heart consists of four chambers. The top two chambers are the atria. The singular form of atria is atrium. The two bottom chambers are the ventricles. The atria only pump blood to the ventricles, so they do not need to be very muscular. The ventricles have thicker muscular walls than the atria. The right ventricle sends blood out to the lungs, while the left ventricle sends blood out to the body. The left ventricle is the thickest chamber of the heart because it sends blood the longest distance. The atria receive blood from veins and the ventricles send blood out to the arteries. In addition, the heart is also divided left to right by the septum. Slide 3 Heart valves Do you recall that there were valves present in the veins? The purpose of these valves was to keep the blood flowing in one direction. The heart also contains valves that serve the same purpose. Valves in the heart are found between the atria and ventricles, as well as between the ventricles and arteries leading out of the heart. When blood travels from the atria to the ventricles, the valves between these chambers will be open, at other times these valves are closed. Slide 4 Pulmonary versus systemic circuit Do you recall that the right ventricle sends blood out to the lungs? This is the pulmonary circuit, sending the blood to the lungs and back to the heart. In the pulmonary circuit the blood leaves the heart deoxygenated and returns to the heart oxygenated. The left ventricle sends blood to the body. This is the systemic circuit, sending blood to the body and back to the heart. In the systemic circuit the blood leaving the heart is oxygenated and is deoxygenated when it returns to the heart. Slide 5 Simple model of the heart Now let’s look at a simple model of the heart, which will assist you in understanding the flow of blood through the heart and around the body. Looking at the diagram it would appear as if the heart is backwards, because the left side of the heart is on your right and the right side of the heart is on your left. Keep this in mind when studying the heart. Now let’s focus our attention on the atria and ventricles. Between the right atrium and right ventricles is the tricuspid valve. The valve between the left atrium and left ventricle is called the bicuspid or mitral valve. The wall between the right and left sides of the heart is called the septum.
The Heart Slide 6 Blood flow The left side of the heart sends blood to the body and the vessel coming off the left ventricle is the largest artery in the body, the aorta. Blood will travel from the aorta, into arteries, then flow into arterioles, into the capillary beds, and finally return back to the heart through venules and veins. There are two large veins that return blood from the body to the heart. They are the superior cava and the inferior vena cava. These vessels return blood into the right atrium. When the blood returns from the body it is deoxygenated; therefore the first thing the heart has to do is send the blood to the lungs for it to be oxygenated. Blood flows from the right atrium into the right ventricle and into the pulmonary artery through the semilunar valve. Blood will return from the lungs in an oxygenated state through the pulmonary veins. The pulmonary veins connect to the heart at the left atrium. Oxygenated blood then flows into the left ventricle and back out to the body through the aorta; another semilunar valve lies between the left ventricle and the aorta. Slide 7 Heartbeat How does the heart beat? When you listen to a heart beat you are hearing the closing of the valves within the heart. The “lub” sound of a heart beat is the closing of the tricuspid and bicuspid valves, while the “dub” sound is the closing of the two semilunar valves between the ventricles and the arteries. The heart first gets a signal to contract. The signal is received by the SA node. The SA node is also known as the pacemaker. The SA node is located in the right atrium of the heart. The SA node will send a signal to the AV node, which is located in the right ventricle of the heart. Both atria contract at the same time, pushing their blood into the ventricles. As the atria contract, the tricuspid and bicuspid valves are open. The atria stop contracting and these valves close. The AV node delays the signal for contraction, so that the ventricles have the time necessary to fill with blood. Both ventricles then contract at the same time. As the ventricles contract the semilunar valves open. When the ventricles relax, the semilunar valves close. The entire process is repeated. Slide 8 Check Your Understanding Now that we have learned about the heart, let’s check your knowledge of the subject. The following slides will have a series of questions on the topic. Be sure to click “Submit” after answering each question. Slides 9 through 13 Pulmonary and Systemic Circulation Interactive Quiz A nongraded assessment of your knowledge of pulmonary and systemic circulation.
The Heart Slide 14 Heart Attack Most of us know that things can go wrong with the heart. A heart attack occurs when the cells of the heart become starved for blood. These cells become starved because the coronary arteries that are responsible for transporting oxygen and nutrient rich blood to the heart become blocked. Without oxygen the heart cells can not make ATP and begin to die. Coronary arteries can become blocked by the deposition of a substance called plaque that is composed of cholesterol. Do you remember that we said that cholesterol is a structural component of the cell membrane? Cholesterol does not dissolve in the blood because it is a lipid; therefore to move around the body, the cholesterol must be bound to a protein. There are two types of proteins that transport cholesterol, LDL and HDL. HDL moves cholesterol to the liver, so that is can be disposed of, you want to have a lot of HDL. LDL keeps cholesterol circulating in the blood. Eventually this LDL gets caught on the sides of arteries. This has an accumulative effect and more and more LDL gets caught. Other things like red blood cells may also get caught. Eventually the wall to the artery can become damaged and a clot may form. The formation of plaque decreases the diameter of the blood vessels. This disease is called atherosclerosis or hardening of the arteries. Slide 15 Atherosclerosis Why is atherosclerosis called hardening of the arteries? Think about what happens when you stand on a garden hose so that you decrease the diameter of the hose. You reduce the amount of water that can get through the hose. The side of the hose nearest the spout will feel stiff because of the increasing water pressure. The same situation occurs in a blocked artery. The artery before the blockage becomes stiff because of the high amount of pressure caused by the blood moving through a small diameter. Slide 16 Consequences of atherosclerosis The consequences of atherosclerosis can be devastating. Heart attacks can occur as well as strokes. Strokes can occur when an artery in the brain in blocked, or when one of the clots formed to seal a damaged artery moves to the brain. Clots can also break off and move to the limbs causing what is called peripheral vascular disease. Slide 17 Heart disease risk factors There are many risk factors for heart disease. Some of these risk factors include: obesity, high blood pressure, smoking, and high cholesterol. How can you prevent heart disease? Controlling or losing weight, stopping smoking, reducing cholesterol in the diet, managing high blood pressure, and exercising regularly are some ways to prevent heart disease.
The Heart Slide 18 Angioplasty What happens when an artery is blocked? When an artery is blocked, doctors will remove the blockage if possible. To remove a blockage, a procedure called an angioplasty is often performed. In an angioplasty, a small tube is inserted in a vein in the leg and is moved toward the heart. The tube has a balloon attached that moves the plaque out of the way. A stint is left in place to leave the artery open. A stint is like scaffolding that provides structure to the artery. Slide 19 Bypass Surgery If the blockage can not be removed doctors may have to perform surgery. In a bypass surgery, a piece of vein, usually from the leg, is stitched in place to reroute the flow of blood to the heart. The new blood vessel bypasses the blocked artery. If one artery is bypassed it is known as a single bypass, two arteries are called a double bypass, three arteries are called a triple bypass and so on. Slide 20 Check Your Understanding Now that we have learned about heart disease, let’s check your knowledge of the subject. The following slides will have a series of questions on the topic. Be sure to click “Submit” after answering each question. Slides 21 through 26 Preventing Heart Disease Interactive Quiz A nongraded assessment of your knowledge of heart disease. Slide 27 Summary This slide is a summary of all of the “Check Your Understanding” questions from this lecture. Be sure to review the questions you answered incorrectly. Slide 28 Review of the Heart YouTube video Heart Anatomy

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