Chapter 15

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Chapter 15
Cardiovascular System
15.1 Introduction
1. Match the structure and its function. (Outcome 15.1)
1. Arteries—E
2. Arterioles—E
3. Capillaries—A
4. Venules—C, D
5. Veins—F
6. Heart—B
15.2 Structure of the Heart
2. Describe the pericardium. (Outcome 15.2)
The pericardium consists of an outer fibrous bag know as the fibrous pericardium that surrounds a more delicate, double-layered sac. The inner layer of the sac, the visceral pericardium covers the heart. At the base of the heart, the visceral layer turns back upon itself to become the parietal pericardium, which forms the inner lining of the fibrous pericardium. 3. Compare the layers of the heart wall. (Outcome 15.2)

The epicardium (visceral pericardium) functions as a protective layer. This layer consists of connective tissue covered by epithelium. Its deeper portion often contains adipose tissue. The myocardium is relatively thick and consists largely of cardiac muscle tissue. The muscle fibers are arranged in planes, separated by connective tissues, which are richly supplied with blood capillaries, lymph capillaries, and nerve fibers. The endocardium consists of epithelium and connective tissue containing many elastic and collagenous fibers. The connective tissues house the Purkinje fibers, which function with the conduction system of the heart. This layer is continuous with the inner linings of the blood vessels attached to the heart. 4. Draw a heart and label the chambers and valves. (Outcome 15.3) The upper chambers are called atria. These have relatively thin walls and receive blood returning to the heart. The lower chambers are called ventricles. They receive blood from the atria and force blood out of the heart into the arteries. There are two atrioventricular valves (A-V valves). The tricuspid valve is located between the right atrium and the right ventricle. The bicuspid (mitral) valve is located between the left atrium and the left ventricle. There are two semilunar valves. The pulmonary semilunar valve is found between the right ventricle and the pulmonary artery. The aortic semilunar valve is found between the left ventricle and the aorta. All four valves function to prevent backflow between the respective chambers and vessels. 5. Blood flows through the vena cava and coronary sinus into the right atrium, through the __________ _________ to the right ventricle, through the pulmonary valve to the pulmonary trunk into the right and left __________ ___________ to the lungs, then leaves the lungs through the pulmonary veins and flows into the ___________ ___________, through the mitral valve to the ______________ ____________, and through the __________ _________ to the aorta. (Outcome 15.4) tricuspid valve, pulmonary arteries, left atrium, left ventricle, 6. List the vessels through which blood flows from the aorta to the myocardium and back to the right atrium. (Outcome 15.4) The blood is supplied to the tissues of the heart by the first two branches of the aorta called the right and left coronary arteries. The openings to these vessels lie just beyond the aortic semilunar valve. It then goes through the capillary system of the heart. Branches of the cardiac veins that roughly parallel the coronary arteries drain the blood that has passed through the capillaries. These veins empty into the coronary sinus that is located on the posterior side of the heart emptying into the right atrium. 15.3 Heart Actions

7. Describe the pressure changes in the atria and ventricles during a cardiac cycle. (Outcome 15.5) When the atria are relaxed, the pressure begins to rise as they fill with blood. As the atria contract, the pressure raises suddenly, forcing the remaining blood into the ventricles. Pressure is low in the ventricles when they are filling but begins to rise as they fill with blood. It rises sharply as the ventricles contract forcing the blood out into the appropriate vessels. 8. Explain the origin of heart sounds. (Outcome 15.5)

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