Implantation 4 Flashcards

Explain how the placenta can maintain extensive fetal growth in the third trimester despite only a relatively small increase in placental size.

1
Q

What happens to the placenta in the third trimester?

A

Weight will increase from about 300 grams at 28-30 weeks gestation to about 500 grams at term

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

How does the placenta provide adequate nutrition and gas exchange when the fetal mass is effectively outgrowing the placental mass in the third trimester of pregnancy?

A
  • Increased branching of the secondary and tertiary villi into smaller terminal villi at term
    • effectively increases surface area of the villi in contact with the maternal blood without having to increase overall placental mass
  • Within the terminal villi, fetal capillaries are essentially directly subadjacent to the syncytiotrophoblast layer
    • decreases diffusion distance
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

How will the placenta respond if the fetus experiences chronic hypoxia/ischemia in utero prior to term?

A
  • Villi will become smaller sooner
    • tries to increase surface area
    • leads to improper growth of the placenta
    • referred to as hypermature villi, distal villous hypoplasia, or Tenney-Parker change
  • Local ischemic/hypoxic change in the placenta results in clumping of the syncytiotrophoblast nuclei into “knots”
How well did you know this?
1
Not at all
2
3
4
5
Perfectly