Question

Typical lub-dub sounds in heart beat are due to
A. Closing of the bicuspid and tricuspid valve.
B. Closing of the semilunar valve.
C. Blood under pressure through aorta.
D. Closure of bicuspid-tricuspid valve followed by semilunar valves.

Answer 1

Hint:
The heart is a muscular organ in most animals, which pumps blood through the blood vessels of the circulatory system.
The pumped blood carries oxygen and nutrients to the body while carrying metabolic waste such as carbon dioxide to the lungs.
In humans the heart is located between the lungs.

Complete answer:
The heart is a muscular organ located just behind and slightly left of the breastbone.
The heart pumps blood through the network of arteries and veins called the cardiovascular system.
The heart has four chambers:
1. The right atrium
2. The right ventricle
3. The left atrium.
4. The left ventricle
Heart beat: Heartbeat is defined as the pulse of your heart.
When the heart pulses and pumps blood throughout your body, this is an example of a heartbeat.
So, according to the given question, typical lub-dub sounds in heart beat is due to
In healthy adults, there are two normal heart sounds often known as a lub and a dub.
It occurs in sequence with each heartbeat.
These are the first heart sound ${S_1}$) and second heart sound (${S_2}$), produced by the closing of the AV valves (the mitral valve and the tricuspid valve) and semilunar valves (the pulmonary valve and the aortic valve), respectively.

So, the correct option is option D. Closure of bicuspid-tricuspid valve followed by semilunar valves.

Note:
Mitral valve is located between the left atrium and the left ventricle
It is also known as the bicuspid valve because it has two cusps (anterior and posterior).
Like the tricuspid valve, the base of each cusp is secured to a fibrous ring that surrounds the orifice.