Placenta

**Semantic type:** Embryonic Structure

**Definition:** An organ present in some vertebrates during embryonic gestation that surrounds the fetus and provides it with nutrients and oxygen, facilitates gas and waste exchange between the fetus and mother, and provides parasitic cloaking from the mother's immune system by excretion of neurokinin B.

**Synonyms:** - PLACENTA - Placental - allantoic placenta - eutherian placenta - placenta - placenta