Human Anatomy Vol 1

THORAX

Table 1

Right ventricle

Thinner than left, 1/3 thickness of

Left Ventricle

Pushes blood only to the lungs

Contains three small papillary muscles

Cavity is crescentic

Contains deoxygenated blood

Forms 2/3rd sternocostal and 1/3rd

diaphragmatic surfaces

of right ventricle and left ventricle

Left ventricle

Much thicker than right, 3 times thicker than right

ventricle

Pushes blood to top of the body and down to the toes

Contains two strong papillary muscles

Cavity is circular

Contains oxygenated blood

Forms 1/3rd sternocostal and 2l3rd diaphragmatic surfaces

Pulmonary

valve

Tricuspid valve

Bicuspid valve

Aortic valve

Papillary muscle

lnterventricu lar

septum

margin, and an atrial and a ventricular surface.

The atrial surface is smooth (Fig. 18.15). The free

margins and ventricular surfaces are rough and

irregular due to the attachment of chordae

tendinae. The aaloes are closed during aentricular

systole (Greekcontraction)by apposition of the atrial

surfaces near the serrated margins (Fig. 18.15).

c. The chordae t€ndinae cormect the free margins and

ventricular surfaces of the cusps to the apices of the

papillary muscles. They prevent eversion of the

free margins and limit the amount of ballooning

of the cusps towards the cavity of the atrium.

d. The atrioventricular valves are kept competent by

active contraction of the papillary muscles, which

pull on the chordae tendinae during ventricular

systole. Each papillary muscle is connected to the

contiguous halves of two cusps (Figs 18.13 and

18.18).

Blood vessels are present only in the fibrous ring and

in the basal one-third of the cusps. Nutrition to the

central two-thirds of the cusps is derived directly

from the blood in the cavity of the heart.

Left coronary

artery

Right coronary

artery

Fig. 18,18: Structure of the aortic valve

3 The tricuspid valve has three cusps and can admit

the tips of three fingers. The three cusps, the anterior,

posterior or inferior, and septal lie against the three

walls of the ventricle. Of the three papillary muscles,

the anterior is the largest, the inferior is smaller and

irregular, and the septal is represented by a number

of small muscular elevations.

4 The mitral or bicuspid valve has two cusps, a large

anterior or aortic cusp, and a small posterior cusp. It

admits the tips of two fingers. The anterior cusp lies

between the mitral and aortic orifices. The mitral

cusps are smaller and thicker than those of the

tricuspid valve.

Semilunor Volves

L The aortic and pulmonary valves are called semilunar

valves because their cusps are semilunar in shape.

Both valves are similar to each other (Fig. 78.17).

2 Each valve has three cusps which are attached

directly to the vessel wall, there being no fibrous ring.

The cusps form small pockets with their mouths

directed away from the ventricular cavity. The free

Fig. 18.17: lnterior of hearl