Trophoblast

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Chorionic villi are part of a normal pregnancy. They are derived from the conceptus, i.e. NOT maternal.

Tumours arising from the trophoblast are dealt with in gestational trophoblastic disease.

Chorionic villi 101

  • Maternal blood is around villi.
  • Fetal blood (nucleated (fetal) RBCs) in the villi.

Basic histology

  • Outer layer of villus: syncytiotrophoblasts.
  • Beneath syncytiotrophoblast (and closer to fetus) cytotrophoblasts.

Chorionic villi 102

  • Syncytiotrophoblasts (eosinophilic cytoplasm with vacuoles (contain hCG), multiple hyperchromatic nuclei).
    • Large + many irreg. or lobular hyperchromatic nuclei.
    • Eosinophilic vacuolated cytoplasm (contains hCG).
    • Closest to mom - covers cytotrophoblast.[1]
  • Cytotrophoblasts (polygonal shape, distinct borders, clear cytoplasm, in cords, single nucleus).
    • Polygonal shaped cells in cords/masses.
    • Distinct cell borders.
    • Covered by syncytiobrophoblast[2] - closer to fetus than syncytiotrophoblasts.
    • Clear cytoplasm.
    • Single uniform nucleus.

Age of villi

Young villi

Old villi

  • Blood vessels present and at the periphery of villus - contain nucleated (fetal) RBCs.
  • Syncytial knots.

See also

References