-
Placenta
- 1/4 is maternal-fetal interface
- outermost cells of chorion laeve appose maternal decidua (3/4 interface)
- Maternal surface: basal plate; lobules= cotyledons, spiral arteries
- Fetal surface: beneath amnion is chorionic plate= layer of CT containing chorionic vessel (branced off umbilical vessels)
- Arteries over veins
-
Amnion
- very thin, tensile strength
- avascular
- covers placenta (fetal side) and umbilical cord
-
Chorion laeve (smooth chorion)
- derived from outerlayer of blasocyst= trophoblast
- multiple layer of trophoblast (cytotrophoblast)
- outermost cells appose maternal decidua (3/4 interface)
- Outer reflected fetal membrane
- thin, avascular
-
Placenta Villi
- close but separate
- bloods Villi extends from chorionic plate
- Intervillous space- maternal blood, bathes outside of villi
- branching of villi and fetal vessels inside of them
- anchoring villi- attached to maternal decidua
- Syncytiotrophoblast: no cell boundaries, come from fusion of cytotroph; bracnched microvilli
- Cytotrophoblast: innermost, stem cell of the lining
- macrophages
-
Villi
villi form all the way around, degenerate leaving multiple layers of cytotrophoblast = chorion laeve
-
Placental barrier
- Early (first trimester): syncytiotrophoblast, cytotrophoblast, mesenchyme, fetal endothelial cells
- As placenta grow, less cytotroph
- Late (third trimester): sycytiotrophoblast and endothelia cells
-
Maternal vascular adaptation
endovascular trophoblast invade spiral arteries, replace m, so can't react to vasoconstrictors, keeps wide open conduit of blood supply to placenta, prevetn hypertention
|
|
