placenty

Placenty is the fetal–maternal organ that forms during pregnancy in mammals to connect the developing fetus to the uterine wall. It mediates nutrient and gas exchange, removes fetal waste, and produces hormones that support gestation. The placenty consists of fetal tissues, including the chorion and placental villi, and maternal tissues, notably the decidua. The key exchange interface is the network of villous trees in which fetal blood vessels come into close proximity with maternal blood within intervillous spaces.

Development and structure begin shortly after implantation. Trophoblast cells differentiate to create the chorionic villi, which invade the maternal decidua and become vascularized. Depending on species, the placenta may present different architectures (for example, discoidal and cotyledonary forms in different mammals) but all share the basic function of fostering directed exchange between blood supplies. The placental barrier is relatively thin, allowing efficient transfer of nutrients such as glucose, amino acids, and fatty acids, as well as oxygen, while enabling removal of carbon dioxide and other wastes.

Hormonal and endocrine roles are central to placenty function. In humans and some other mammals, placental hormones (including human chorionic gonadotropin, progesterone, estrogens, and placental lactogen) help maintain pregnancy, regulate fetal growth, and prepare the mother for birth and lactation.

Clinical relevance includes a range of placental conditions that can affect pregnancy outcomes, such as abnormal placental implantation (placenta accreta spectrum), placenta previa, placental abruption, infection (chorioamnionitis), and disorders like preeclampsia or fetal growth restriction. Variation in placenty structure and function is a key factor in reproductive biology across mammal species.