Implantation 5

Question 1

What happens to the maternal spiral arteries in the first tirmester?

Answer 1

Invaded by extravillous trophoblast cells top open them up and widen their lumens joining into the sinusoidal intervillous spaces

Question 2

Why must the maternal spiral arteries become eroded and invaded by cytotrophoblasts?

Answer 2

• When not pregnant, these vessels are reactive to cytokines, especailly when hypoxic/ischemic
  
  • constrict to divert blood away from the uterus
• During pregnancy, don’t want the fetus to be deprived of oxygen
  
  • Outer smooth muscle is replaced by extravillous trophoblast cells that function as the endothelium during pregnancy
• Effectively diminishes artery reactivity and helps maintain uterine circulation even when hypoxic/ischemic
• Early on, trophoblastic cellular plugs occlude vessels to create hypoxic environment
  
  • thought to facilitate placental growth and differentiation through vasculogenesis and angiogenesis
  • plugs broken down when remodeling is complete