Implantation 6 Flashcards

List the gross and histologic features of a normal placenta.

1
Q

What are the major components of the placenta?

A
  • Membranes
  • Umbilical cord
  • Placental disc
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2
Q

What are the major membranes of the placenta?

A
  • Amnion
    • lines amniotic sac
    • single layer of cuboidal epithelium, basement membrane, and collagen layer
  • Chorion
    • fibrous chorion and a layer of extravillous trophoblast
    • lies deep to the amnion and has sparsely cellular collagen layer
  • Decidual layer
    • maternal in origin
    • contains decidualized maternal cells, vessels, fibrin
    • some degree of hemorrhage here
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3
Q

Describe the histology of the umbilical cord.

A
  • Single layer of cuboidal amniotic epithelium on the outer surface
  • Three vessels, 2 arteries and a veinembedded in a myxoid paucicellular matrix called Wharton’s gelly
    • proteoglycans with some fibroblasts and macrophages
    • vein carries nutrient rich blood to fetus
    • arteries carry deoxygenated blood and waste products back to placenta
  • Can show remnant blood vessels (vitelline) and epithelial remnants (omphalomesenteric and allantoic in origin
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4
Q

What are the major components of the placental disk?

A
  • Chorionic plate
  • Basal plate
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5
Q

Describe the histological features of the chorionic plate.

A
  • Single layer of cuboidal amniotic epithelium overlying a paucicellular collagenous matrix (fibrous chorion)
  • Below are fetal villi separated by blood containing spaces where maternal blood circulates around fetal villi (intervillous space)
    • stem villi - fetal vessels with smooth muscle layers
    • terminal villi - only have capillaries
    • outer layer of syncitiotrophoblast cells
      • true syncytium, no membranes separating nuclei
    • inner layer is cytotrophoblast cells that act as stem cells, become less numerous as development progresses
  • Macrophages (Hofbauer cells) and fibroblasts in cellular matrix of villi
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6
Q

Describe the histological features of the basal plate of the placental disk.

A
  • Extravillous trophoblast cells
  • Decidualized maternal cells
    • maternal endometrial stromal cells
    • form interface between fetal tissues and maternal myometrium
  • Two well defined fibrinoid layers
    • Rohr’s fibrinoid and Nitabuch’s fibrinoid (deeper layer)
  • Maternal vessels
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