Placentation is the process by which the placenta, a vital organ in pregnancy, develops and functions in the womb of a pregnant mammal. The placenta serves several key roles, including:
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Nutrient Transfer: It facilitates the transfer of nutrients and oxygen from the mother to the developing fetus while removing waste products from the fetus’s blood.
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Hormone Production: The placenta produces hormones that are crucial for maintaining pregnancy, including human chorionic gonadotropin (hCG), progesterone, and estrogen.
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Immunological Protection: It helps protect the fetus from the mother's immune system, which would otherwise recognize the fetus as foreign tissue.
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Barrier Function: The placenta acts as a selective barrier to certain substances, allowing some (like antibodies) to pass through while keeping out others (like many pathogens).
Placentation can vary among different species, leading to different types of placentation patterns, such as:
- Deciduate: Where a significant portion of the maternal tissue is shed at birth (e.g., humans).
- Adeciduate: Where minimal maternal tissue is lost (e.g., pigs).
- Endotheliochorial: The chorion is in contact with the endometrium (e.g., dogs and cats).
- Epitheliochorial: The chorion is in contact with the uterine epithelium (e.g., pigs and horses).
The structure and type of placentation can play a significant role in the development of the fetus and the health of both the mother and child during pregnancy.