On the outside of the heart is the pericardium, a two-layered membrane sac that protects the heart and secretes a fluid that lubricates the heart to reduce friction. It also keeps the heart together as it continuously contracts and relaxes (1).
There are many blood vessels that connect to the heart. Blood vessels that take blood from the heart to the body are called arteries. Blood vessels that take blood from the body to the heart are called veins. Arteries are more elastic than veins, and their walls are thicker and contain more smooth muscle than the walls of veins. This lets the arteries expand and contract under the pressure that the heart exerts against the artery walls as it pumps blood (2).
The inside of the heart is divided into four chambers, two atria and two ventricles. The four chambers are divided into left and right. Each side (left or right) has one atrium and one ventricle. The right side of the heart pumps blood only to the lungs, so it is not as large and muscular as the left side of the heart, which pumps blood to the whole body. The right side of the heart contains deoxygenated blood, while the left side of the heart contains oxygenated blood (12).
The atria are the superior chambers that receives blood from the veins and pumps it into the ventricles. On top of each atrium is a dogear-like pouch that increases the blood volume of the atria so they can receive more blood from the veins (3). Since the atria only have to pump blood to the ventricles, their walls are not as thick and muscular as the walls of the ventricles, which have to pump blood to the lungs or to the whole body (4).
The atria are separated from the ventricles by atrioventricular valves, which prevent blood in the ventricles from flowing back into the atria when the ventricles contract. The atrioventricular valves, which are the tricuspid and bicuspid (mitral) valves, are "anchored" by the chordae tendinae, which are long fibers that trail off the valve, and the papillary muscle, which attach the chordae tendinae to the wall of the ventricle. This makes sure the valves close properly and keeps the valves from swinging backwards into the atria so that blood does not leak backwards into the atria. If valves are not anchored properly, blood could leak backwards instead of going where it needs to go, which could cause health problems like fatigue, swelling, or heart palpitations (irregular heartbeat) (7).
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| drawing of aortic semilunar valve (11) |
Valve failure on different sides of the heart has different effects. If valvular heart disease occurs on the right side of the heart, swelling in the feet and ankles occurs because blood that is pumped into the right ventricle by the right atrium does not stay in the right ventricle. Instead, it flows back into the right atrium, backing up the blood flow and not letting blood from the body flow into the right atrium. As a result, blood collects in the feet and ankles, causing them to swell up (10a).
If valvular heart disease occurs on the left side of the heart, the body would not be able to get as much blood. Body cells would not get as much oxygen, which would cause fatigue. This is because blood in the aorta that is supposed to be pumped to the body by the left ventricle instead flows back into the left ventricle and does not go to the body (10b).
At the very end of the dissection, we made a frontal cut through the heart to separate the anterior (front) and posterior (back) sides. This way we were able to see all the structures inside the heart.
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| drawing of interior of heart (13) |
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