L24: Development Cardiovascular system

Question 1

How is foetal circulation reversed with the onset of the first breath?

Answer 1

Mechanically: Foetal lungs are collapsed, compressing vasculature and creating high resistance circulation. This is reverse with the first breath.

Vasomotor: Foetal arteriolar vasoconstriction is maintained by low O2 in foetal pulmonary flow, reversed with first breath.

loss of placenta = increase in arterial systemic resistance

Question 2

What is found at the umbilical cord?

Answer 2

2x umbilical arteries
umbilical veins (1 ruminants + carnivores, 2 in others)
Urachus (bladder- allantoic cavity)

Question 3

What are the 3 important shunts that characterise foetal circulation

Answer 3

Ductus venosus
Foramen ovale
Ductus arteriosus

Question 4

describe the ductus venosus

Answer 4

oxygenated blood from mums placenta > umbilical vein > wide ductus venous channel in the liver –> bypasses hepatic sinusoids –> direct to the Caudal VC

Question 5

Describe the foramen ovale

Answer 5

opening at septum between RA and LA to enable O2 blood to bypass pulmonary circulation (less resistance)

Preferentially delivered to heart and brain from LV

Question 6

Describe the ductus arteriosus

Answer 6

Connection between aorta and pulmonary trunk, diverting majority of output from RA away from lungs

Question 7

upon the first few breaths, sudden great increase in pulmonary blood flow increases venous return to the _____

Answer 7

Left atrium

Question 8

the foetal arterial circulation is a ____ ______ pathway whilst the pulmonary circulation is a ____ ______ pathway

Answer 8

low resistance

high resistance

Question 9

what are the two foetal extra-embryonic circulations

Answer 9

1. yolk sac (vitelline circulation)

2. allantoic/umbilical circulation

Question 10

what are the two foetal intra-thoracic circulations

Answer 10

3. systemic circulation

4. pulmonary circulation

Question 11

describe the pathway for the vitelline circulation

Answer 11

aorta –> yolk sac = omphalo-messenteric artery

yolk sac –> aorta = omphalo-messenteric vein, merge into common cardinal vein

Question 12

describe the pathway for the allantoic circulation

Answer 12

brnches of the dorsal aorta –> allantois = allantoic/umbilical artery
allantois –> heart = paired umbilical veins

Question 13

describe the pathway for the systemic circulation

Answer 13

heart –> embryonic body = paired ventral and dorsal aorta
embryonic body –> heart = paired cardinal veins 1. paired anterior cardinal, 2. paired posterior cardinal. both merge into common cardinal