Explain the function of heart.
Answers
The Function of heart:
Deoxygenated blood is received by the heart from the body through superior and inferior vena cava. The superior vana-cava carries deoxygenated blood from the upper region and inferior vena-cava(which is larger than the superior one) from the lower region of the body.
The blood from both the vena-cava is received by the right atrium. Right atrium also receives blood from coronary sinuses(vessels of the heart itself). This blood (deoxygenated) flows into the right ventrical. The opening between the right aurical and ventrical is guarded by a bicuspid valve called the mitral valve. Now blood from right ventricle is pumped into the lungs(for oxygenation) through the pulmonary artery.
After the blood is oxygenated in the lungs, it is again received by the heart…in the left atrium through the pulmonary vein. Now the blood from left atrium flows into the left ventricle. The opening of the left atrium and ventricle is guarded by the tricuspid valve.
The left ventricle is now containing the oxygenated blood which is pumped through the aorta and reaches all the organs through arteries.
The most vital function of heart is heart beats which takes place all the time throughout one’s life. The sequence of events which takes place during the completion of one heart beat is called the cardiac cycle. It involves repeated rhythmic contraction and relaxation of heart muscles. Contraction is called systole and relaxation is called diastole. The cardiac cycle involves the following:
During the timewhen the muscles of all four chambers of the heart are relaxed, the blood returning to the heart under low pressure in the veins enters the two atria. Blood from large veins, called vena cava pours into right atrium. This blood comes from head, upper body parts and lower body parts where oxygen has been used up and the blood is free from oxygen i.e., deoxygenated. Thus, the deoxygenated blood enters the right atrium. At the same time, the pulmonary vein from lungs pour oxygenated blood into the left atrium. Thus, the oxygenated blood enters the left atrium.
As the right and left atria fill with blood, pressure in them rises so that the valves between left atrium and left ventricle (bicuspid valve) and between right atrium and right ventricle (tricuspid valve) open and the atria contract. Atrial contraction (artrial systole) forces pumping of deoxygenated blood from right atrium into the right ventricle through tricuspid valve and oxygenated blood from left atrium into left ventricle through bicuspid valve.
Almost immediately the ventricles contract. This is called ventricular systole. During contraction of ventricles, the deoxygenated blood from right ventricle flows to the lungs through pulmonary artery and the oxygenated blood from left ventricle is distributed to all the parts of the body through the largest artery, called aorta.