Heart valves.

Directional blood flow through the heart is accomplished by valves in the adult human heart and a series of shunts in the fetal heart.

The human heart has four main valves (and some remnants from the fetal shunts that will be discussed in another section).

Atrioventricular valves

2 atrioventricular valves are located between the atria and the ventricles.
These valves prevent blood flowing back into the atria during the systolic phase of the heart cycle (contraction of the ventricles).

Heart strings (chordae tendineae) and papillary muscles firmly anchores the leaflets of the valves to the ventricle wall to prevent folding back (prolapse) of the leaflets during systole (contraction of the ventricles).

• The mitral or bicuspid valve (2 leaflets) seperate the left chambers.
• The tricuspid valve (3 leaflets) seperate the right chambers.

Semilunar valves

There are 2 semilunar (half-moon shaped cusps) valves found in the aortic and pulmonary vessels.
These smaller valves prevent blood flowing back into the heart during diastole (relaxation of the ventricles).

• Aortic valve
• Pulmonary (also sometimes called Pulmonic) valve

Tip:

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