Human Anatomy Vol 1

THORAX

Upper limb trunkPulmonary

Foramen

ovale

Pulmonary

artery

lnferior vena cava

Ductus

Umbilical

vetn

Umbilical afteries

Fig. 18"32: Details of foetal circulation. Percentage of oxygen

in blood vessels is put in numbers

left pulmonary artery. The left pulmonary artery is

joined to the left end of arch of aorta via the 'ductus

arteriosus'. Thus the venous blood traversing through

the left pulmonary artery and ductus arteriosus enters

the left end of arch of aorta. So the descending thoracic

and abdominal aortae get mixed blood. At the internal

iliac end it passes via the two umbilical arteries to

reach the placenta for oxygenation.

So for bypassing the lungs and for providing oxygen

and nutrition to the developing embryo and foetus, the

following structures had to be improvised.

a. One umbilical vein

b. Ductus venosus

c. Foramen ovale

d. Ductus arteriosus

e. Two umbilical arteries.

At the time of birth, with the start of breathing

process, these structures (1-5) retrogress and gradually

the adult form of circulation takes over.

Changes at birth:

Lungs start functioning.

Umbilical vein forms ligamentum teres.

Ductus venosus forms ligamentum venosum.

Foramen ovale closes.

Ductus arteriosus forms ligamentum arteriosum.

Umbilical arteries form medial umbilical ligaments.

Mnemonics

Heart valves"Try Pulling My Aorta"

Tricuspid

Pulmonary

Mitral

Aorta

Heart is a pump for pushing blood to the lungs

and for rest of the organs of the body. Due to

sympathetic stimulation it is felt thumping against

the chest wall.

All the components of left ventricle are thicker as

it has to push the blood from top of head to the

toes of foot.

Left atrium forms most of the base of the heart.

Coronary arteries are functional end arteries.

Pain of heart due to myocardial infarction is

referred to left side of chest between 3rd and 6th

intercostal spaces. It also get extended to medial

side of left upper limb in the area of distribution

of C8 and T1 spinal segments.

Case L

An adult man was stabbed on his upper left side of

chest. He was taken to the casualty department of

the hospital. The casualty physician noted that the

stab wound was in left third intercostal space close

to the sternum. Further the patient has engorged

veins on the neck and face.

o What is the site of injury?

. Why are the veins of the neck and face engorged?
. What procedure would be done as an emergency
measure before taking him to operation theatre?
Ans: The injurir is in left third intercostal space
inju g the pericarcliurn and right ventricle, causing

Brain, head and neck

I r) Arch of aorta

Ductus

arteriosus

r'., a.

b.

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d.

e.

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