Trophoblast

Source: Wikipedia, the free encyclopedia.
Trophoblast
Blastocyst with an inner cell mass and trophoblast.
Details
Days6
Gives rise tocaul
Identifiers
Latintrophoblastus; massa cellularis externa
MeSHD014327
TEE6.0.1.1.2.0.2
FMA83029
Anatomical terminology

The trophoblast (from

egg to become extraembryonic structures that do not directly contribute to the embryo. After blastulation, the trophoblast is contiguous with the ectoderm of the embryo and is referred to as the trophectoderm. [4] After the first differentiation, the cells in the human embryo lose their totipotency because they can no longer form a trophoblast. They become pluripotent
stem cells.

Structure

Image showing trophoblast differentiated into the two layers of cytotrophoblast and syncytiotrophoblast during implantation

The trophoblast proliferates and differentiates into two cell layers at approximately six days after fertilization for humans.

Layer Location Description
Cytotrophoblast The inner layer A single-celled inner layer of the trophoblast.
Syncytiotrophoblast The outer layer A thick layer that lacks cell boundaries and grows into the
stroma. It secretes hCG in order to maintain progesterone
secretion and sustain a pregnancy.
Intermediate trophoblast (IT) The implantation site, chorion, villi (dependent on subtype) An anchor placenta (implantation site IT).

Function

Trophoblasts are specialized cells of the placenta that play an important role in embryo implantation and interaction with the decidualized maternal uterus.[5] The core of placental villi contain mesenchymal cells and placental blood vessels that are directly connected to the fetus’ circulation via the umbilical cord. This core is surrounded by two layers of trophoblasts, the cytotrophoblast and the syncytiotrophoblast. The cytotrophoblast is a layer of mono-nucleated cells that resides underneath the syncytiotrophoblast.[6] The syncytiotrophoblast is composed of fused cytotrophoblasts which then form a layer that covers the placental surface.[6] The syncytiotrophoblast is in direct contact with the maternal blood that reaches the placental surface. It then facilitates the exchange of nutrients, wastes and gases between the maternal and fetal systems.

In addition, cytotrophoblasts in the tips of villi can differentiate into another type of trophoblast called the

spiral arteries as they remodel these vessels into wide bore conduits that are independent of maternal vasoconstriction. This ensures that the fetus receives a steady supply of blood, and the placenta is not subjected to fluctuations in oxygen that could cause it damage.[7]

Clinical significance

The invasion of a specific type of trophoblast (extravillous trophoblast) into the maternal

placenta percreta
.

Gestational trophoblastic disease is a pregnancy-associated concept, forming from the villous and extravillous trophoblast cells in the placenta.[8]

Choriocarcinoma are trophoblastic tumors that form in the uterus from villous cells.[8]

Trophoblast stem cells (TSCs) are cells that can regenerate and they are similar to embryonic stem cells (ESCs) in the fact that they come from early on in the trophoblast lifetime.[9] In the placenta, these stem cells are able to differentiate into any trophoblast cell because they are pluripotent.[9]

Additional images

  • Blastodermic vesicle of Vespertilio murinus.
    Blastodermic vesicle of Vespertilio murinus.
  • Section through embryonic disk of Vespertilio murinus.
    Section through embryonic disk of Vespertilio murinus.
  • Transverse section of a chorionic villus.
    Transverse section of a chorionic villus.
  • Scheme of placental circulation.
    Scheme of placental circulation.
  • The initial stages of human embryogenesis
    The initial stages of
    human embryogenesis
  • Histopathology of a chorionic villus, in a tubal pregnancy, with labeled cytotrophoblasts and syncytiotrophoblasts.
    Histopathology of a
    tubal pregnancy
    , with labeled cytotrophoblasts and syncytiotrophoblasts.

See also

References

  1. S2CID 208378249
    .
  2. ISBN 978-0-12-815145-7
    .
  3. PMID 28110754
    .
  4. PMID 19299251
    .
  5. PMID 28110755
    .
  6. ^ a b "The trophoblast". Archived from the original on 15 December 2007.
  7. PMID 17288592
    .
  8. ^
    PMID 31001418
    .
  9. ^
    PMID 24220516
    .

External links
Retrieved from "https://en.wikipedia.org/w/index.php?title=Trophoblast&oldid=1175838729"