Question

Describe the structure and working of the human heart.

[Review question: Pg. No: 215]

Answer 1

1. The human heart is four chambered. The two upper thin walled chambers of the heart are called auricle or atria (sing: atrium) and two lower thick walled chambers are called ventricles.
2. The chambers are separated by partition called septum. The septum between auricles and ventricles prevents the mixing of oxygenated and deoxygenated blood.
3. The two auricles are separated from each other by interatrial septum.
4. The left atrium is smaller than the right atrium. The right atrium receives deoxygenated blood from different parts of the body through the main veins superior vena cava, inferior vena cava and coronary sinus.
5. Pulmonary veins bring oxygenated blood to the left atrium from the lungs. The right and left auricles pump blood into the right and left ventricles respectively.
6. The ventricles form the lower part of the heart. The two ventricles are separated from each other by an interventricular septum.
7. The left and right ventricles have thick walls because the ventricles have to pump out blood with force away from the heart. From the right ventricle arises the pulmonary trunk which bifurcates to form right and left pulmonary arteries.
8. The right and left pulmonary arteries supply deoxygenated blood to the lungs of the respective side.
9. The left ventricle is longer and narrower than the right ventricle. The walls are about three times thicker than the right ventricle. The left ventricle gives rise to aorta.
10. The oxygenated blood is supplied by the aorta to various organs of the body.
11. The coronary arteries supply blood to the heart.
12. Right atrioventricular valve: It is located between the right auricle and right ventricle
13. Left atrioventricular valve: It is located between the left auricle and left ventricle.
14. Semilunar valves: The major arteries (pulmonary artery and aorta) which leave the heart have semilunar valves which prevent backward flow of blood into the ventricles.