Human Anatomy Vol 1

THORAX

3 Right ventricle
a. Rough part-proximal portio of bulbus cordis
(Fig. 18.12).
b. Smooth par he conus cordis or middle portion
of bulbus cordis.
4 Left ventricle (Fig. 18.15)
a. Rough part-whole of primitive ventricular
chamber.
b. The conus cordis or the middle portion of bulbus
cordis forms the smooth part.
5 Interatrial septum
a. Septum pri rum-fossa ovalis.
b. Septum secundum-limbus fossa ovalis.
6 Interventricular septum
a. Thick muscular in lower part by the two ventricles.
b. Thin memb anous in upper part by fusion of
inferior atrioventricular cushion and right and
left conus swelling. Membranous part not only
separates the two ventricles, but also separates
right atrium from left ventricle
7 Truncus arteriosus or distal part of bulbus cordis
forms the ascending aorta and pulmonary trunk,
as separated by spiral septum.
Spiral septum is responsible for triple relation of
ascending aorta and pulmonary trunk. At the beginning
pulmonary trunk is anterior to ascending aorta, then it
is to the left and finally the right pulmonary artery is
posterior to ascending aorta (Fig. 18.10).
Heart is fully functional at the end of second month
of intrauterine life.

Sympathetic chain

Superior cervical

ganglion

Middle cervical

ganglion

lnferior cervical

ganglion

T1 ganglion

T2 ganglion

T3 ganglion

T4 ganglion

T5 ganglion

From recurrent

laryngeal nerve

given in the ihorax

The foetus (Greek offspring) is dependent for its entire

nutrition on the mother, and this is achieved through

the placenta attached to the uterus. As the lungs are

not functioning, the blood needs to bypass the

pulmonary circuit. The oxygenated blood reaches the

foetus through the single 'umbilical vein'. This vein

containing oxygenated blood traverses the umbilical

cord to reach the liver. The oxygenated blood bypasses

the liver via 'the ductus venosus/ to join inferior vena

cava. As inferior vena cava drains into the right atrium,

the oxygenated and nutrient rich blood brought by it

enters the right atrium. Then it passes into the left

atrium through 'foramen ovale', thus bypassing the

pulmonary circuit (Figs 18.31 and 18.32).

From the left atrium it enters the left ventricle and

traverses the systemic circuit via the ascending aotta,

arch of aorta and descending thoracic and descending

abdominal aortae. The last mentioned vessel divides

into common iliac arteries. Each common iliac artery

terminates by dividing into external and intemal iliac

arteries. Arising from two internal iliac arteries are

the two umbilical arteries which in turn pass through

the umbilical cord to end in the placenta.

The deoxygenated blood from the viscera, lower

limbs, head and neck and upper limbs also enters the

right atrium via both the inferior and superior vena

cava. This venous blood gains entry into the right

ventricle and leaves it via the pulmonary trunk and

Sympathetic chain

Superior cervical

ganglion

Middle cervical

ganglion

lnferior cervical

ganglion

Tl ganglion

T2 ganglion

T3 ganglion

T4 ganglion

T5 ganglion

Fig. 18.30: Formation of superficial and deep cardiac plexuses