Question

Differentiate between the following pairs on the basis of the criteria mentioned in the brackets.
LUB and DUB (names of the valves whose closure produce the sound).

Answer 1

The sounds are made by the heart when the valves contract and relax. Atrio- ventricular and semilunar valves are involved in this process. These two are first and second sounds made by heart. There is also a third and fourth heart sound, known as gallops. These are low-frequency sounds which can be associated with pathological reasons.

Complete answer:
The human heart is a muscular organ with four chambers. The size of the heart is about the clenched fist. It is located between the lungs in the thoracic cavity, slightly towards the left of the sternum (breastbone).

Valves are flaps of fibrous tissues located in the cardiac chambers between the veins. They ensure that the blood flows in a single direction (unidirectional). Flaps also prevent the blood from flowing backward. Valves in a heart - atrioventricular valves, tricuspid valves, mitral valves, and the semilunar valves. Based on their function, valves are of two types:

Atrioventricular valves - are between ventricles and atria. The valve between the right ventricle and right atrium is the tricuspid valve, and the one which is found between the left ventricle and left atrium is known as the mitral valve.

Semilunar valves - are located between the left ventricle and aorta. It is also found between the pulmonary artery and the right ventricle.

The period between the end of one heartbeat to the end of the next heartbeat is called a cardiac cycle. The cardiac cycle is formed of three phases – atrial systole, ventricular systole, and joint diastole.

During ventricular systole, the closing of auriculoventricular valves at the start of the ventricular systole produces the first heart sound called lub or systolic sound.

During joint diastole, the rapid closure of semilunar valves at the beginning of the ventricular diastole produces the second heart sound called dub.

Note: There are two major sounds lub and dup, known as S1 and S2 respectively. The elapsing period between the primary heart sound and second sound defines systole (ventricular ejection) and therefore the before the time between the second sound and the following first sound defines diastole (ventricular filling). There is also a third and a fourth heart sound, S3, and S4.
The early diastolic filling in which gallop is associated is the S3 and may be heard pathologically in such states as volume overload and left ventricular systolic dysfunction. The S4 may be a late diastolic sound and should be heard in such pathologic states as uncontrolled hypertension.