Placenta

Question 1

What are the two main components of the placenta?

Answer 1

Decidua basalis - (MATERNAL COMP)

** also decidua parietalis (opp side of uterus) and decidua capsularis which fuse near end of pregnancy as amniotic cavity takes up whole uterus

Chorion frondosum - FETAL COMP)

Question 2

3 Types of Trophoblasts that Differentiate

Answer 2

• 1- Villous syncytiotrophoblasts - hormonally active
• 2- Anchoring trophoblasts - columns of cells that make direct contact w/ decidua for anchoring placenta into uterus
• 3- Extravillous trophoblasts - go out into endometrium to remodel uterine vasculature; remove and remodel smooth muscle of spiral arteries; now dilated and lined w/ these trophoblasts that act as new endothelium of arteries
  
  • In direct contact w/ maternal blood

Question 3

What are placental villi? How do they change throughout pregnancy?

Answer 3

• Site of exchange b/n maternal and fetal blood
• Maternal blood comes in thru spiral arteries and is dumped into blood pools that surround the villi
• The villi themselves contain fetal capillaries (branch off umbilical arteries and vein)
• Progression w/ Pregnancy (cont inc surface area)
  - Primary Villi - simple; mainly syncytiotrophoblasts
  - Secondary Villi - add mesoderm layer too
  - Tertiary Villi - now much less syncytiotrophoblast layer; much smaller diffusion barrier b/n maternal and fetal blood
• Vessels torn at birth BUT firm uterine contraction prevents postpartum hemorrhage

Question 4

Cotyledons

Answer 4

Functional Unit

• Ea has own blood flow; redundancy so okay even if some infarct
• Formed by invaginations of decidua forming individual cotyledon units

Question 5

4 Types of Placental Transport (examples of ea)

Answer 5

1- Passive - O2 (fetal Hb has greater affinity), CO2, electrolytes, fat-soluble vitamins

2- Facilitated Diffusion - glucose (GLUT1 and GLUT3); crosses freely if glucose gradient

3- Active Transport - AA (multiple transporters), Ca, iron, iodine, phosphate, water-soluble vitamins
- Compromise of AA transporters - restricts fetal growth

4- Receptor Endocytosis - IgG, FAs, LDL

Question 6

Hormones Prod by Syncytiotrophoblasts (3)

Answer 6

• hCG
• Estrogen / Progesterone
• Human placental lactogen

Question 7

Hormones Prod by Decidua (5)

Answer 7

• Prolactin
• Relaxin (cervical changes and ligaments and renal changes early in pregnancy)
• Prostaglandins
• Cortisol
• VEGF