a-short-review-of-histology

The Placenta:

The placenta is formed in pregnancy, mainly to provide a mechanism for the transfer of nutrients from mother to embryo/foetus
The development of the placenta, and its gross structure, are considered elsewhere
The transfer of nutrients is achieved largely by the development within the placenta of placental villi
Placental villi go through a number of developmental stages but the villi which are finally formed, and which are active participants in aiding maternal-foetal transfer of nutrients, are called tertiary villi
Tertiary villi are covered with a layer of syncytiotrophoblast
This syncytiotrophoblast is exposed to the maternal blood
Deep to the syncytiotrophoblast is a layer of cytortrophoblast but as pregnancy progresses this layer becomes thinner, incomplete and eventually disappears
Deep to the trophoblast layer(s) is connective tissue supporting a network of foetal capillaries
These capillaries receive the nutrients which pass across the trophoblast layer from the maternal blood
The foetal capillaries in the villi form part of the foetal blood circulation

Placenta: "Foetal" Aspect

The "foetal" aspect of the placenta showing the umbilical vessels that carry blood between the foetus and the placental villi

Placenta: "Maternal" Aspect