what is a placenta

The placenta is a temporary embryonic and later fetal organ that develops in the uterus during pregnancy. It connects the developing baby to the mother through the uterine wall and is linked to the fetus by the umbilical cord. Its main functions are to provide oxygen and nutrients to the baby and to remove waste products from the baby's blood. The placenta acts as a critical interface for nutrient, gas, and waste exchange between the maternal and fetal blood circulations, without the two blood supplies mixing directly. It also has an important endocrine role, producing hormones that regulate both maternal and fetal physiology throughout pregnancy. Structurally, the placenta is generally flat and round, about 20-22 cm long and 2-2.5 cm thick in humans, weighing around 500 grams (about 1 pound). It has two sides: a maternal side attached to the uterine wall and a fetal side connected to the fetus via the umbilical cord. The umbilical cord contains blood vessels that transport oxygen-rich blood to the baby and carry waste-laden blood back to the placenta for disposal by the mother's body. The placenta begins forming soon after conception, starting from the blastocyst stage, and continues growing throughout pregnancy until delivery. After birth, the placenta is expelled from the uterus, sometimes referred to as the "afterbirth." In summary, the placenta is an essential organ for fetal development during pregnancy as it transports nutrients and oxygen to the fetus, removes waste, and produces hormones that support pregnancy and fetal growth. This organ is unique to mammals and some other species, and its name derives from Latin and Greek words meaning "flat, slab-like," reflecting its typical appearance.