What is Placenta? Definition, Types, & Examples

What is Placenta?

Placenta comes from a Latin word which means flat cake. In botany, placenta refers to the ovules which arises from the ovary in flowering plants and in non-flowering plants it refers to spores.

In zoology, it refers to an organ which is present in female mammals, during offspring generation and through this organ the nutrition and necessary requirements reaches the fetus from the mother and it also excretes out waste substances.

Placenta is an organ, which is seen in mammals during gestation, when a mother keeps her child within her womb. Through this organ, mother and the fetus are connected and endocrine secretion as well as transfer of substances and fluids takes place through the uterine opposition and the vascularized trophoblastic parts.

Diffuse, zonary, discoid, cotyledonary and diffuse are the variants of vascular apposition and the apposition nature could be villious or labyrinthine, whereas the apposition closeness depends on the layers which are lost between the blood of mother and fetus.

Placenta weighs around 600 gram is of 2 cm in thickness with a diameter of 16cm. from the allantois or the yolk, chorion may obtain blood vessels, and while giving birth, chorion may drop off with the uterine lining or might remain as well as separate itself.

Thus, placenta can be villious, chorioallantoic, haemochorial or discoid. To the intervillious space, which consist of the maternal blood the chorionic villi fuses. The side facing the outer part of the uterus consist of 20 bumps on placenta which occurs due to grouping up of villi and forming cotyledons.

The part facing the fetus, which is the inner lining is smooth and coated with amnion, which is a thin layer, lining the chorion as well as the corners excluding the umbilical cord and this chord connects to the placenta at the center but may also come in contact from non-placental chorion edges.

The vital function is to provide food and oxygen and the fetus waste as well is transferred from the chord. From the mother’s blood supply, the nourishment reaches due to the formation of the structure on the wall of uterus. In botany, placenta refers to the ovules which arises from the ovary in flowering plants and in non-flowering plants it refers to spores.

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