Placentation

Placentation refers to the development and formation of the placenta in the uterus during pregnancy. It is a crucial process in the reproductive cycle of mammals, including humans, as it facilitates the exchange of nutrients, gases, and wastes between the mother and the fetus.

Types of Placentation

There are several types of placentation, each characterized by the arrangement of ovules within the ovary. These include:

• Axile Placentation: In this type, the placenta is formed along the central axis of the ovary, with the ovules attached to it. This is common in plants with a superior ovary, such as Primulaceae and Ranunculaceae.

• Parietal Placentation: Here, the ovules are attached to the outer wall of the ovary. This is common in plants with an inferior ovary, such as Brassicaceae.

• Free Central Placentation: In this type, the ovules are attached to a free-standing column in the center of the ovary. This is seen in plants like Primrose.

• Basal Placentation: Here, a single ovule is attached to the base of the ovary. This is seen in plants like Sunflower.

Placentation in Mammals

In mammals, placentation refers to the formation of the placenta, a vital organ that facilitates the exchange of nutrients, gases, and wastes between the mother and the fetus. The type of placentation varies among different species. In humans, it is classified as deciduous and hemochorial where the entire maternal endometrium is involved and the placental cells directly contact the mother's blood.

See Also

• Placenta
• Ovary
• Pregnancy

Placentation Resources
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