The trophoblast is made up of an internal layer of cubical or prismatic cells, the cytotrophoblast or layer of Langhans, and an external layer of richly nucleated protoplasm devoid of cell boundaries, the syncytiotrophoblast.
The chorionic villi are at first small and non-vascular, and consist of the trophoblast only, but they increase in size and ramify, whereas the mesoderm, carrying branches of the umbilical vessels, grows into them, and, in this way, are vascularized.
Blood is carried to the villi by the branches of the umbilical arteries, and, after circulating through the capillaries of the villi, is returned to the embryo by the umbilical veins. Until about the end of the second month of pregnancy, the villi cover the entire chorion, and are almost uniform in size; but, after this, they develop unequally.
On the other hand, the villi on that part of the chorion which is in contact with the decidua placentalis increase greatly in size and complexity, and hence this part is named the chorion frondosum.
The predictors of retained products of conception following first-trimester pregnancy termination with manual vacuum aspiration
Jun 01, 2006; ABSTRACT Objective To identify the risk factors associated with retained products of conception (RPC) following first-trimester...