Placentar

Placentar is a verb occasionally used in discussions of embryology to denote the action of forming or developing the placenta during pregnancy. In standard medical terminology, the process is usually called placentation, and in Spanish-speaking contexts it is often referred to as placentación. The term placentar may appear in educational texts as an inflected form, but it is not common in clinical practice.

Placentation begins after the embryo implants into the uterine lining and involves the coordinated interaction between fetal trophoblast cells and maternal tissue. The placenta develops as fetal membranes invade the maternal endometrium and establish blood vessels to enable the transfer of substances between mother and fetus. In humans, the placenta is discoid and hemochorial, meaning fetal blood is in direct contact with maternal blood through the chorionic villi, though placentation differs among species in structure and degree of invasion.

Functions of the placenta include the exchange of gases (oxygen and carbon dioxide) and nutrients, removal of wastes, and the production of hormones that support pregnancy. Hormones such as progesterone and estrogens help maintain the gestational environment, and other placental hormones contribute to metabolic and immune regulation. The placenta also serves as a barrier between maternal and fetal circulations and participates in immune modulation.

Variation exists across mammals in placentation type, reflecting differences in how many maternal tissue layers separate the fetal and maternal blood. Abnormal placentation can be associated with pregnancy complications, including growth restriction, preeclampsia, and placenta previa or abruption.

See also: placentation, placenta, gestation.