Transition To Extrauterine Life

Question 1

What happens each week in fetal development?

Answer 1

Week1-zygote travels down Fallopian tube. Once zygote reaches the uterus it is termed ‘blastocyte’. It implants itself into the endothelial lining of the uterine wall.
Week2-implantation of blastocyte initiates placenta development
Week 3-angiogenesis begins
Week3-8-main embryonic period, major organ development
Week9-40-fetal period, period of maturation

Question 2

What are the 3 main fetal shunts?

Answer 2

1. Ductus venosous
2. Foramen ovals
3. Ductus arteriosis

Question 3

What is the process of fetal circulation?

Answer 3

1. Blood from umbilical vein splits between the liver and ductus venosous
2. Ductus venosous connects to IVC, mixes oxygenated blood and deoxygenated blood-goes into right atrium and deoxygenated blood from SVC
3. Due to increase pressure, blood shunted through foramen ovale into the left atrium-left ventricle-aorta
4. Most of blood bypasses lungs through ductus arteriosis-descending aorta-umbilical arteries-placenta

Question 4

Why is there high pulmonary vascular resistance and low systemic vascular resistance?

Answer 4

High PVR- nonareated lungs and decreased oxygen tension causes vasoconstriction
Low SVR- large volume of blood in placenta and due to the ductus arteriosis shunt

Question 5

What are the 5 phases of lung development?

Answer 5

1. Embryonic (week 6)
2. Pseudoglandular (week 7-16)
3. Canallcular (week 17-26)
4. Saccular (week 27-35/6)
5. Alveolar (week 36-term)

Question 6

When do the kidneys begin to produce urine?

Answer 6

Between 10-12th week of gestation

Question 7

Why are cortisol and thyroid hormone important leading up to and during labor?

Answer 7

Because they help regulate fluid absorption from the lungs. Cortisol levels are lower in preterm neonates/c-section

Question 8

What causes the baby to take its first breath?

Answer 8

Low O2, high CO2, low PH and a change in temp, stimulates respiratory center in brain.