Question

What is the duration between the closure of atrioventricular valves that is lubb and closure of semilunar valves that is dubb ?
A) 0.3 s
B) 0.5 s
C) 0.1 s
D) 0.6 s

Answer 1

During a cardiac cycle , there is a contraction of both the ventricles called as ventricular systole . The duration of ventricular systole is the same as that of the duration between the heart sounds like lubb and dubb.

Complete answer:

Human heart is myogenic and mesodermal in origin which is situated in the middle of the thoracic cavity between the two lungs in the space called as mediastinum.Its size matches with the size of a clenched fist.
The covering of the heart is pericardium which has two layers such as fibrous pericardium and serous pericardium.The outer layer is called fibrous pericardium and the inner layer is serous pericardium.
In between the parietal layer and the visceral layer of the serous pericardium , there is a pericardial space filled with pericardial fluid which acts as a shock absorber and prevents the heart wall from desiccation.
The heart has two upper smaller chambers called atria and two lower bigger chambers called ventricles.An inter atrial septum is present between the two atria and an inter ventricular septum is present between the two ventricles which prevents the bloods from mixing.
Deoxygenated blood from the body enters the right atrium and the oxygenated blood from the lungs enters the left atrium.The blood from atria enters the ventricles and then the right ventricle pumps the blood towards lungs whereas the left ventricles pumps blood to the whole of the body.
All these events constitute a single heartbeat or the cardiac cycle which lasts for 0.8 secs. A single cardiac cycle includes atrial systole , ventricular systole and a joint diastole. All these events can be studied in an electrocardiograph.
The atrioventricular valves are present between an atrium and a ventricle of the same side which prevent the backflow of blood from ventricles to the atrium.Semilunar valves are present in the pulmonary artery and the dorsal aorta.
In a cardiac cycle , atrial systole or atrial contraction lasts for 0.1 secs , ventricular systole or ventricular contraction lasts for 0.3 secs , and joint diastole that is relaxation lasts for 0.4 secs.
During the ventricular systole , atrioventricular valves are closed which makes the lub sound and then there is a closure of semilunar valves which makes the dub sound.

Note: Both these sounds that are lubb and the dubb are of great importance in studying clinical diagnosis . These two sounds can be heard by using a stethoscope which helps us to study tachycardia that is increased heartbeat and bradycardia that is decreased heart beat.