Indeciduate Placenta || Types || Diffuse || Cotyledonary || Intermediate

Diffuse type

        The example of diffuse indeciduate placenta comes from the horse, the pig and some other ungulates. The chorionic villi are uniformly distributed all over the surface of blastocyst but are absent at the extreme end of the blastodermic pit. The blastocyst is enclosed within the elongated uterus like the inner tube present a bicycle type. So the uniform distribution of villi is of great advantage and a contact between foetal tissue and maternal tissue is maintained throughout the surface of blastocyst.

Cotyledonary type

        In cotyledonary indeciduate placenta, the distribution of villi is not uniform but the villi are confined to particular tufts or bunches so that only some part of surface is provided with villi. These groups of villi are called the cotyledons and hence the placenta is named as cotyledonary placenta. The uterus is also developed in the same way so that the cotyledons establish a contact with uterine wall. This type of adaptation is encountered with the cow where the uterus is thickened at places and in these the cotyledons of the blastocyst fit properly. [Such thickenings of uterine wall are called caruncles. The caruncles present many crypts or depressions which accommodate all the villi of the cotyledons. The cotyledonary indeciduate placenta occurs in mammals like cow, sheep and deer.

Intermediate type

        The third form of indeciduate placenta, the intermediate type is not much common as the other two are. As the name suggests, it is an intermediary between the diffuse and cotyledonary indeciduate placenta. Here cotyledons are present on the surface of blastocyst but between the two cotyledons are type of placenta is present in the embryo of giraffe.