Human Anatomy Vol 1

Sternocostal/anterior su rface

2l3rd 1/3rd

lnterventricular septum

Anterior interventricular groove

Aortic orifice

Left ventricle

Anterior papillary muscle

Mitral orifice

Posterior papillary muscle

Posterior interventricular groove

1l3rd 2l3rd

Diaphragmatic/inferior s u rface

Fig. 18.15: Schematic transverse section through the ventricles of the heart showing the atrioventricular orifices, papillary muscles,
and the pulmonary and aortic orifices

is the largest (Fig. 78.12). The posterior or inferior

muscle is small and irregular. The septal muscle is

divided into a number of little nipples. Each

papillary muscle is attached by chordae tendinae

to the contiguous sides of two cusps (Fig. 18.13).

The septomarginal trabecula or moderator band is

a muscular ridge extending from the ventricular

septum to the base of the anterior papillary muscle.

It contains the right branch of the AV bundle

(Figs 18.12 and L8.14).

The cavity of the right ventricle is crescentic in section

because of the forward bulge of the interventricular

septum (Fig. 18.15).

Fig. 18.13: Structure of an atrioventricular valve

Pulmonary orifice

Right Ventricle

Septal papillary muscle

Tricuspid orifiCe

Anterior papillary muscle

Posterior or inferior papillary muscle

PERICARDIUM AND HEART

SA node

AV bundle and

left branch

AV node

Right branch of

AV bundle

Purkinje fibres

Moderator band

Fig. 18.14: The conducting system of the heart

5 The wall of the right ventricle is thirurer than that

of the left ventricle in a ratio of 1:3.

!nlervenlilculol Seplum

The septum is placed obliquely. Its one sudace faces

forwards and to the right and the other faces backwards

and to the left. The upper part of the septum is thin

and membranous and separa-tes not only the two

ventricles but also the right atrium and left ventricle.

The lower part is thick muscular and separates the two

ventricles. Its position is indicated by the anterior and

posterior interventricular grooves (Fig. 18.15).

Fibrous ring Cusp