Human Anatomy Vol 1

THORAX

Feolules

The heart is a conical hollow muscular organ situated
in the middle mediastinum. It is enclosed within the
pericardium. It pumps blood to various parts of the
body to meet their nutritive requirements. The Greek
name for the heart is cardin from which we have the
adjective cardia. The Latin name for the heart is cor from
which we have the adjective cororutry.
The heart is placed obliquely behind the body of the
sternum and adjoining parts of the costal cartilages, so
that one-third of it lies to the right and two-thirds to
the left of the median p1ane. The direction of blood flow,
from atria to the ventricles is downwards forwards and
to the left. The heart measures about^12 x^9 cm and
weighs about 300 g in males and^250 g in females.

EXIERNAT FEATURES

The human heart has four chambers. These are the right

and left atria and the right and left ventricles. The atria

(Latin chamber) lie above and behind the ventricles. On

the surface of the heart, they are separated from the

ventricles by an atrioventricular groove. The atria are

separated from each other by an interatrial groove. The

ventricles are separated from each other by an

interventricular groove, which is subdivided into

anterior and posterior parts (Fig. 18.7).

Right border Upper border

Left anterior part

of coronary (AV)

sulcus

The surfaces are demarcated by upper, inferior, right

and left borders.

Grooves or Sulci

The atria are separated from the ventricles by a circular

atrioaentricular or coronary sulcus. It is divided into

anterior and posterior parts. Anterior part consists of

right and left halves. Right half is oblique between right

auricle and right ventricle, lodging right coronary

artery. Left part is small between left auricle and left

ventricle, lodges circumflex branch of left coronary.

The coronary sulcus is overlapped anteriorly by the

ascending aorta and the pulmonary trunk. The inter-

atrial grootse is faintly visible posteriorly, while ante-

riorly it is hidden by the aorta and pulmonary trunk.

TIne anterior interaentricular grootse is nearer to the left

margin of the heart. It runs downwards and to the left.

The lower end of the groove separates the apex from

the rest of the inferior border of the heart. The posterior

interaentricular grootse is situated on the diaphragmatic

or inferior surface of the heart. It is nearer to the right

margin of this surface (Fig. 18.8). The two

interventricular grooves meet at the inferior border near

the apex.

The crux of the heart is the point where posterior

interventricular sulcus meets the coronary sulcus.

Apex of the Heort

Apex of the heart is formed entirely by the left ventricle.

It is directed downwards, forwards and to the left and

is overlapped by the anterior border of the left lung. It

is situated in the left fifth intercostal space 9 cm lateral

to the midstemal line just medial to the midclavicular

line. In the living subject, pulsations may be seen and

felt over this region (Fig. 18.7).

In children below 2years, apex is situated in the left

fourth intercostal space in midclavicular line.

Right Upper border

anterior part

of coronary

(AV) sulcus

Left border

Anterior

interventri-

cular sulcus

Apex Posterior part

of coronary

(AV) sulcus

Left surface

Superior

vena cava

Right

pulmonary

VEINS

Fig. 18.7: Gross features: Sternocostal sufface of heart

The heart has

. An apex directed downwards, forwards and to
the left,
. Abase (posterior surface) directedbackwards; and
. Anterior/sternocostal
. Inferior and
. Left lateral surfaces.

lnferior border

Fig. 18.8: The posterior aspect of the heart