Changes at birth

Question 1

How does the foetus obtain its oxygen?

Answer 1

From the maternal circulation via the placenta

Question 2

Where does the umbilical vein take the oxygenaged blood?

Answer 2

Through the liver via the hepatic sinusoids and ductus venosus

Question 3

Where is the majority of the blood returned via the caudal vena cava diverted through?

Answer 3

The foramen ovale to the left atrium

Question 4

The diversion of blood to the foramen ovale is assisted by a structure at the mouth of the caudal vena cava known as … ?

Answer 4

The Eustachian valve

Question 5

What happens to the oxygenated blood in the left atrium?

Answer 5

Mixed with a small volume of deoxygenated blood from the pulmonary veins

Question 6

Through which vessel is blood redirected to the aorta from the pulmonary trunk?

Answer 6

Ductus arteriosus

Question 7

Where receive the first portions of oxygenated blood and why?

Answer 7

The brachiocephalic trunk and coronary circulation receive the first portions (for the brain and cardiac muscle)

Question 8

What are the two main differences in foetal circulation compared to outside the womb?

Answer 8

• oxygenated blood is arriving from the placenta via the systemic venous system, rather than from the lungs
• oxygenated blood enters the right rather than the left atrium

Question 9

At birth what stops blood flow from the neonate to the placenta?

Answer 9

Contraction of the umbilical arteries

Question 10

Where can the remnants of
1) the umbilical vein
2) the umbilical artery
Be seen in an adult?

Answer 10

1. round ligament of the liver

2. round ligament of the bladder

Question 11

Describe the events following a neonates first breath

Answer 11

• lungs expand so pulmonary capillaries are pulled open
• huge drop in resistance to the right side of the heart, afterload decreases
• large increase in blood flow to the lungs
• increased venous return to the left atrium
• pressure causes the foramen ovale to close (remnant = fossa ovalis)