Placenta

Throughout pregnancy, the placenta serves as the fetus’s food source and guardian. It stands out because it is a temporary organ that develops along with the fetus throughout pregnancy before being expelled along with it at delivery.

• The placenta is occasionally referred to as the “afterbirth” since it is discharged vaginally after the fetus is delivered.
• Mammals have a temporary organ called the placenta that connects the mother’s uterus to the fetus during pregnancy.
• Only in the case of animals can it be found.
• Materials can be transported because of the umbilical cord’s connection between the placenta and the fetus.
• The uterus and placenta are typically connected at the top, bottom, side, front, or back.
• Placenta previa is a condition in which the placenta connects to the lower part of the uterus in extreme circumstances.

Types of Placenta

Depending on the Involvement of Embryo­nic Tissue

1. Yolk-Sac Placenta: The moment that the extraembryonic somatopleure and the midgut extension of the splanchnopleure encapsulating the yolk merge, allowing the embryo to make contact with the uterine wall. Examples: Mustelus.
2. Chorio-Allantok Placenta: In order to make touch with the uterine tissue, the extraembryonic somatopleure joins forces with the allantoic evagination of the hindgut. Examples include Eutherian animals and the Chalcides lizard.

Depending on the Distribution of Villi

1. Diffused Placenta: The villi are numerous and evenly dispersed over the entire chorion. Ungulates and Cetacea are two examples.
2. Cotyledonary placenta: In particular areas, the villi group together to create tiny tufts. Ruminants are an example.
3. Zonary Placenta: On the chorion, the villi are restricted to an annular zone. Examples include Carnivora (Pinnipedia).
4. Discoidal Placenta: Iruro-dents and insectivores can be seen with their villi constrained to a discoidal area. The placenta in humans and apes is of the metadiscoidal type.

Based on the Relationship of Villi with the Uterine Wall

1. Deciduate Placenta: The mucous membrane of the uterine wall, which emerges with the embryo at birth, develops an intimate connection with the villi.
2. Indeciduate or Adeciduate Placenta: The uterine walls, which detach from the uterus during birth, are weakly connected to the villi.

Based on the Degree of Involvement of Foetal and Maternal Tissues

1. Epitheliochortal Placenta: The uterine epithelium and the embryo’s chorion continue to be in simple apposition. Horse and pig, for instance.
2.  Syndesmochorial Placenta: The uterine epithelium vanishes, and the chorion makes direct touch with either the glandular epithelium or endometrium. Consider sheep.
3. Vasochorial or Endotheliochorial Placenta: The endometrium and glandular epithelium vanish, and the chorion makes direct contact with the uterine capillary endothelium. Dogs and cats are two examples.
4. Haemochorial Placenta: The endometrium, glandular epithelium, and endothelium of the capillaries vanish, and the chorion is drenched in flowing matern­al blood. Example: A man.
5. Haemoendothelial Placenta: The glan­dular epithelium, endometrium, and endothelium of the maternal blood capillaries vanish, much like that of a placenta of the hemochorial type. The fetal endothelium divides the maternal and fetal circulating bloodstreams as a result of the removal of these maternal structures, which also causes the trophoblastic epithelium (the outer layer of the blastocyst) of the fetus to dissolve. Examples: A lot of mice.

During pregnancy, one or more offspring develop (gestate) in the womb of the pregnant woman. Multiple pregnancies result in multiple births, including twins. Although getting pregnant through sexual activity is most usual, there are additional procedures using assisted reproductive technologies. Pregnancies can end in one of four ways: live birth, spontaneous miscarriage (also known as abortion), artificial abortion (sometimes known as induced miscarriage), or stillbirth. The gestational age is the amount of time following the beginning of the last menstrual period (LMP) when childbirth typically takes place.