Question

1. What surprised you about the anatomy of the sheep’s heart?

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2. Research diseases of the heart valves. How might a valvular insufficiency affect heart function? How would valvular stenosis (tightening or less ability to open easily) affect heart function?

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Answer 1

* Sheep's heart is similar to other mammalian heart except for a little difference. Although the sheep heart is 4-chambered like all other mammalian heart, the apex of the sheep heart is made only of the left ventricle and is blunt in shape. Second, the intervalvular or membranous septum which makes a fibrous continuity between the mitral and aortic valve is absent in sheep heart. The aortic valve leaflets are very thin and fragile.

* The heart valves act as doors and allow blood to flow in only one direction in the heart. There are 4 important heart valves, one each between the atria and the ventricle in each half of the heart and one each between the ventricles and the blood vessels which come out of each of them.

The valve between right atrium and right ventricle is called tricuspid valve and that between the left atrium and left ventricle is called mitral valve. The semilunar valves guarding the opening of the pulmonary artery in the right ventricle is called pulmonary valve and that between the aorta and left ventricle is called aortic valve.

Vulvular eart disease occurs when the heart valves do not function properly. This can be Vulvular insufficiency which occurs when the valves do not close properly and there is a backflow of blood in the heart. This is called 'leaky valve' or regurgitation of blood. Another cause can be hardening of the heart valve which is called Vulvular stenosis. This occurs when the heart valves do not open fully to allow blood flow. This can be due to stiff or fused leaflets of the heart valve.

Heart valve diseases can be congenital, that is, from birth or they can develop later in life due to any infection such as rheumatic fever, endocarditis etc.

* If a person is suffering from vulvular stenosis, the blood flow from the atria to the ventricles will not be sufficient. As a result, when the ventricles contract, there will not be enough blood to pump to different parts of the body. The narrowed opening might make the heart work very hard to pump blood. Overstraining of the heart might lead to heart failure and development of other heart complications.