Gestation and Birth

Question 1

What diffuses between mother and embryo?

Answer 1

• diffusion occurs at placenta
• O2
• H2O
• glucose
• amino acids
• inorganic salts

Question 2

Does maternal blood or fetal blood have a higher partial pressure of O2?

Answer 2

maternal blood (high partial pressure allows for diffusion to lower partial pressure found in fetal blood)

Question 3

Describe fetal hemoglobin (HbF)

Answer 3

• found in fetal blood cells

- have greater affinity for oxygen compared to maternal Hb

Question 4

Where does gas exchange/oxygenation occur in a fetus?

Answer 4

across the placenta because fetal lungs do not function until birth

Question 5

What is the function of the placental barrier?

Answer 5

-immune protection (fetus is immunologically naive but accident exposure to pathogens can happen in utero)

Question 6

What hormones are produced by the placenta?

Answer 6

• progesterone
• estrogen
• human chorionic gonadotropin (hCG)

Question 7

Describe the umbilicial arteries

Answer 7

• carries deoxygenated blood AWAY from the fetus and TOWARDS the placenta
• also carries waste products

Question 8

Describe the umbilical vein

Answer 8

carries oxygenated blood with nutrients TOWARDS the fetus and AWAY from the placenta

Question 9

What are some key differences between fetal circulation and adult circulation?

Answer 9

• lung and liver are not significant prior to birth
• gas exchange occurs at placenta rather than lungs
• detoxification and metabolism primarily controlled by mothers liver
• nutrient and waste exchange occurs at placenta
• fetal lungs and liver are underdeveloped and sensitive to high BP
• right side of fetal heart has a higher pressure than the left side of the heart (opposite in adults)

Question 10

What are shunts?

Answer 10

• developed by the fetus to direct blood away from fetal lungs and liver during development
• 3 shunts: foramen ovale, ductus arteriosus, ductus venosus

Question 11

What vessels/chambers does the foramen ovale connect?

Answer 11

• connects right atrium to the left atrium meaning that blood from the vena cava enters the right atrium and skips the right ventricle so blood is pumped thru aorta directly to systemic circulation
• allows the lungs to be bypassed

Question 12

What vessels/chambers does the ductus arteriosus connect?

Answer 12

• connects pulmonary artery to aorta

- allows the lungs to be bypassed

Question 13

What vessels/chambers does the ductus venosus connect?

Answer 13

• connects the umbilical vein to the inferior vena cava

- allows the liver to be bypassed

Question 14

What happens during first trimester?

Answer 14

• organogenesis occurs (development of heart, eyes, gonads, limbs, liver, brain)
• cartilaginous skeleton begins to harden into bone
• embryo is known as a fetus by the end of 8 weeks

Question 15

What happens during second trimester?

Answer 15

• fetus undergoes tremendous growth
• fetus begins to move within amniotic fluid
• face takes on a human appearance
• toes and fingers elongate

Question 16

What happens during third trimester?

Answer 16

• rapid growth and brain development continue

- transfer of antibodies to fetus

Question 17

What is parturition?

Answer 17

• vaginal childbirth

- accomplished by rhythmic contractions of uterine smooth muscle which is coordinated by prostaglandins and oxytocin

Question 18

Describe the 3 phases of birth

Answer 18

1. cervix thins out and amniotic sac ruptures
2. strong uterine contractions lead to birth of fetus
3. placenta and umbilical cord are expelled (afterbirth)