How the Body Works : Each Heartbeat

With each heartbeat there are two phases in the passage of oxygenated blood and deoxygenated blood through the heart. In the phase of relaxation, or diastole, the heart fills with blood. As the ventricles relax, valves in the aorta and in the pulmonary artery close with a dup sound and blood pours into the two atria from the venae cavae and the pulmonary veins. The mitral and tricuspid valves between the atria and ventricles open, allowing blood into the ventricles. The heart then stops filling with blood. In the phase of contraction, or systole, the heart empties and a lub sound is made by the closing of the mitral and tricuspid valves. This prevents a backflow of blood into the atria as it is pumped from the ventricles into the pulmonary artery and the aorta. Each heartbeat lasts up to eight-tenths of a second, with systole lasting for four-tenths of a second and diastole occupying the remaining time.

Category:

Howto & Style

Tags:

• Each
• Heartbeat

[Chlo1234321]

the man speaking sounds like a ped . :S

[drugdr2010]

it is definitely valve closure... the "lub" is closure of the AV valves, preventing backflow of blood into the atria, and the "dub" is closure of the semilunar valves

[radovichhillary]

like your clip .. keep it up =) thanks

[krsnax1]

@drugdr2010 the valves slamm shut so the blood slamms up against them. So valve closer is part of the process and definately makes it possible but the actual sound is the liquid hitting against them.

[krsnax1]

@drugdr2010 I'm sorry but its not valve closure. Think of a constant force of water pushing towards the shore. The harder the liquid hits the shore the louder the sound. The liquid is rushing through the cardiovascular system constantly. To shut those valves while the blood continues to try to rush through them causes the liquid to slam against them. If the valves were to close slowly, then you probably would not hear such a sound.

[krsnax1]

@nadreas1 you are absolutely correct. Medfro asked for a reference and I have provided it for him/her.

[krsnax1]

@Medifro Sound 2 occurs at the start of diastole (phase 4) when the semilunar valves close. The sounds are not caused by the valve cusps coming together as they shut. They are caused by the turbulent rushing of blood through the valves as they are narrowing and about to close. If you think about the amount of blood that is expelled through the body it makes a lot of sense. I hope this helps. :)

[krsnax1]

@Medifro: reference Principles of human physiology 3rd edit.,C. Stanfield & W. Germann copyright 2009 Pearson Edu.Inc. See ch.13, p.383 "Heart Sounds."

Heart sounds heard through a stethoscope 1. Lubb (low-pitched) 2. Dupp (louder, sharper). Lubb (when you compare it to the timing of the events of the cardiac cycle) occurs at the start of systole, when the AV valves close.

[Spetsop]

Actually the normal heart beat sounds (lub-dub; or the S1 and S2) are produced when the blood hits the valves and forces them to close (thus preventing blood flow back). The abnormal heart sounds (the S3 and S4) are made when blood hits either the walls of the ventricles (S4, in a non-compliant heart) or when blood enters the volume overloaded ventricles (S3).

[deezTX]

Taking A and P and all the books I have read states it's the valves closing.

[Medifro]

I checked my sources and refernces again, and thought about the suggestion our beloved collegue made. Wheneever I think about it ( since frankly its an intresting observation ), it makes no sense, and he's saying its a misconception.

This of course not to mention the various signs that follow the sounds, in ECG, Echo, and pressure-volume graphs.