• Placenta
    • a barrier that prevents blood exchange between mother and fetus but allows exchange of oxygen, carbon dioxide, and nutrients
    • composed of two components
      • fetal
      • maternal
Fetal component
  • Tertiary Chorionic Villi
    • villi that grow from the chorion to increase the surface area for exchange
    • villi that have grown in size, branched, and vascularized
    • inner layer derived from cytotrophoblast
    • outer layer derived from syncytiotrophoblast
      • secretes hCG to maintain the production of progresterone from the corpus luteum during the 1st trimester
      • hCG is a heterodimer that has the same alpha subunit as FSH, LH, and TSH, but beta subunit is what differentiates the hormones 
Maternal component
  • Decidua basalis
    • derived from the endometrium of the uterus
    • shed from mother after birth
    • mother's blood fills the lacunae and gas and nutrient exchange occurs across the fetal portion of the placenta
Placental complications
  • Normal
    • attaches in superior posterior part of uterus 
  • Placenta previa
    • attaches in inferior part of uterus covering internal os, leading to bleeding as uterus dilates during pregnancy
  • Placenta
    • accreta
      • attaches deep in uterus and invades into myometrium but not entirely
    • increta
      • invades entire thickness of myometrium
    • percreta
      • penetrates entire thickness of myometrium and into serosa of uterus leading to possible attachment to bladder or rectum
  • Placenta abruptio
    • prematurely detaches from uterus, associated with maternal hypertension
  • Preeclampsia
    • sudden development of the following after week 20 of gestation
      • maternal hypertension greater than 160/110 mm Hg
      • proteinuria
      • can progress to eclampsia (above conditions plus seizures)

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