Answer
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Hint: During the cardiac cycle, two types of sounds can be heard with the help of stethoscope. The valves present in the heart can cause vibrations and audible sounds. These sounds are ‘lub’ and ‘dub’. The blood entering and exiting the heart causes these types of sounds. The tricuspid valve and the semilunar valve cause ‘lub’ and ‘dub’ sounds.
Complete answer:
The deoxygenated blood enters into the heart from superior vena cava and inferior vena cava. The right atrium takes the deoxygenated blood and the bicuspid valve open so that the blood enters into the right ventricle. The pulmonary arteries take the deoxygenated blood to the lungs. The lungs purify it and transfer it to the pulmonary veins by which it enters into the left atrium. After this, with the help of aorta it is transported to other parts of the body. The semilunar valve is present at the base of the aorta.
The heart sounds are created from the blood flowing through the heart chambers. During the cardiac cycle the cardiac valves open and close during the cardiac cycle. There are mainly four types of the heart valves: tricuspid valve, mitral valve, pulmonic valve, and aortic valve.
The tone lubb is caused by the closure of the mitral and tricuspid atrioventricular valves at the beginning of ventricular systole.
The dub sound is caused by the closure of the aortic valve and pulmonary valve at the end of ventricular systole. It is caused by the semilunar valve or aortic valve.
From the above information we have found that the ‘lub’ and ‘dub’ heart sound are due to closing of heart valves.
Hence, the correct answer is option (C).
Note: The heart valves help to prevent the backflow of the blood. The sounds created by the vibrations in these structures are audible. The turbulence in the blood flow creates more vibrations. The lub sound or the first sound can be heard the loudest. The sound produced by the tricuspid valves is a low pitched, dull sound at the beginning of the ventricular systole.
Complete answer:
The deoxygenated blood enters into the heart from superior vena cava and inferior vena cava. The right atrium takes the deoxygenated blood and the bicuspid valve open so that the blood enters into the right ventricle. The pulmonary arteries take the deoxygenated blood to the lungs. The lungs purify it and transfer it to the pulmonary veins by which it enters into the left atrium. After this, with the help of aorta it is transported to other parts of the body. The semilunar valve is present at the base of the aorta.
The heart sounds are created from the blood flowing through the heart chambers. During the cardiac cycle the cardiac valves open and close during the cardiac cycle. There are mainly four types of the heart valves: tricuspid valve, mitral valve, pulmonic valve, and aortic valve.
The tone lubb is caused by the closure of the mitral and tricuspid atrioventricular valves at the beginning of ventricular systole.
The dub sound is caused by the closure of the aortic valve and pulmonary valve at the end of ventricular systole. It is caused by the semilunar valve or aortic valve.
From the above information we have found that the ‘lub’ and ‘dub’ heart sound are due to closing of heart valves.
Hence, the correct answer is option (C).
Note: The heart valves help to prevent the backflow of the blood. The sounds created by the vibrations in these structures are audible. The turbulence in the blood flow creates more vibrations. The lub sound or the first sound can be heard the loudest. The sound produced by the tricuspid valves is a low pitched, dull sound at the beginning of the ventricular systole.