1. Types of placenta according to nature of fetal membrane:

A : Yolk sac placenta

Example: Kangaroo

B: Chorio allantoic placenta

Chorion + allantoic both involved in the formation of placenta

Example: Eutherian mammals

C: Chorionic placenta

Chorions form villi and villi form placenta.

Example: Humans

2.Types of placenta on the basis of histology:

A: Epitheliochorial placenta

In this type of placenta 6 barriers are present.

Example: Horse pig

B: Syndesmochorial placenta

5 barriers are present between the fetus and the uterus.

Uterine epithelium is absent .

Example: Cow, Sheep, Goat

C: Haemo_chorial placenta

All uterine tissue barriers are absent .

Uterine epithelium absent.

Uterine connective tissue absent.

D: Haemo_endothelial placenta

Three uterine barriers and two fetal barriers are absent only one barrier is present.

Example: Rabbit

3.Types of placenta on the basis of dates of placenta:

A: Non_decidual placenta

No part of uterine placenta is shed out after birth.

Example: 🐎 Horse

B: Deciduate placenta

Few parts of decidua shed out.

Example: Humans

C: Contra_deciduate placenta

Placenta is non decidual even fetal placenta is absorbed.

Example: Bendicoat

4.Types of placenta on the basis of villi of chorion:

A. Diffuse placenta

Villi are present all around the chorion.

Example: Pig Horse

B. Cotyledonary placenta

Two separate patches are present.

Example:Cow 🐄, Sheep 🐑

C. Intermediate placenta

Two separate patches are present with scatter.

Example: Camel 🐪

D. Zonary placenta

Form girdles.

Example: 🐈 cat , 🐕 dog

E. Decoidal placenta

Villi are present at one side of chorion.

Example: 🐀 rat

F. Metadiscoidal placenta

Villi are present first all around the chorion then disappear at one side.

Example: Humans