Question

Which of the following is the correct matching pair?
a) Lub-sharp closure of AV valves at the beginning of ventricular systole
b) Dup-the sudden opening of the semilunar valves at the beginning of ventricular diastole.
c) Pulsation of the radial artery-valves in the blood vessels
d) Purkinje fibers-initiation of the heartbeat

Answer 1

Hint: The closing and opening of the heart valves are responsible for producing sounds of lub dup. The blood enters the heart through the vena cava and transports the blood into the right atrium of the heart. The blood is pushed into the ventricle through the opening of the tricuspid valve. The pulmonary vein transports the blood into the atrium. Then it is transported to the ventricle which is regulated by the mitral valve.

Complete answer:
The heartbeat sounds produced are due to the closure of the atrioventricular valves and the semilunar valves. Lubb is the first sound made by the heart which is when atrioventricular valves close and the ventricles contract. It occurs at the beginning of the ventricular contraction of the ventricular systole.

Additional information:
- Dup sound is the second sound produced by the heart during the blood flow. It occurs due to the closure of the aortic- pulmonary valves and relaxation of the ventricles. This period of the sound from dup to lubb is known as the diastole.
- Purkinje fibers are not directly involved in the starting of the heartbeat. Rather, the sinoatrial node is the group of the cells that are present in the opening of the vena cava. It generates electrical impulses that help in the initiation of the contraction of the muscles present in the atria of the heart. Thus, initiating the heartbeat. It is the pacemaker of the heart.
So, the correct answer is ‘a) Lub-sharp closure of AV valves at the beginning of ventricular systole’.

Note: The tricuspid valves and the bicuspid valves present in the heart help in the flow of blood into the ventricle. They also help in preventing the backflow of blood into the atria. Bicuspid and tricuspid valves together form the atrioventricular valves of the heart.