Maternal Placenta || Types of Placentations
Maternal Placenta
The maternal tissues forming the decidua basalis is composed of two layers of progravid endometrium. One of these layers is compact and other is of loosely arranged cells making it spongy layer. The spongy layer is stretched out at later stages of pregnancy forming horizontal clefts. The compact layer is closely incorporated with the placenta and it is also called the basal plate. The basal plate is composed of fibrinoid tissue and the trophoblast of the anchoring villi Some of the trophoblast form the peripheral shell which makes union with the eroding endometrium At earlier stages, the trophoblast covers the basal plate and becomes discontinuous as pregnancy is prolonged. The basal plate is provided with a number of uterine arteries which are highly branched. The blood vessels lose their necessary coating when they pass obliquely through the basal plate.
There exists a number of different placentae in different groups of mammals. They may be headed as follows:
(1) Yolk sac placenta
(ii) Allantoic placenta
(iii) Indeciduate placenta
(iv) Deciduate placenta
Post a Comment