When hearing a “heart beat”, you are actually hearing the close.
Semilunar valve
Aorta
Pulmonary
artery
Carotid
The correct answer and explanation is:
The correct answer is Semilunar valve.
The sound you hear as a “heartbeat” is primarily caused by the closing of the heart valves during the cardiac cycle. The heart produces two main sounds, commonly referred to as “lub” and “dub.” These sounds correspond to the closing of specific valves in the heart.
The first sound, “lub,” is associated with the closing of the atrioventricular (AV) valves (the mitral and tricuspid valves). This occurs when the ventricles contract, preventing backflow of blood into the atria. The second sound, “dub,” corresponds to the closing of the semilunar valves—specifically the aortic and pulmonary valves. These valves are located at the junction between the ventricles and the major arteries (aorta and pulmonary artery).
The semilunar valves close when the ventricles finish contracting and begin to relax, preventing blood from flowing back into the ventricles from the aorta or pulmonary artery. This closure of the semilunar valves is what creates the “dub” sound. The sound is typically heard more distinctly at the left side of the chest, as the aortic valve is on the left side of the heart, near the aorta.
The aorta and pulmonary arteries themselves do not produce any distinct sound by themselves. The carotid artery, which is a major blood vessel in the neck, does not directly contribute to the sounds of the heartbeat, although it is an important vessel that carries oxygenated blood from the heart to the head and neck.
In summary, the “dub” sound of the heartbeat is caused by the closure of the semilunar valves, located between the ventricles and the large arteries (aorta and pulmonary artery).