1. the innermost membrane that encloses the embryo or fetus of a mammal, bird, or reptile; the amniotic membrane.
Usage: anatomy, biology; also called amniotic membrane

Examples

• The amnios protects the developing fetus throughout pregnancy.
• During ultrasound, doctors can observe the amnios surrounding the baby.
• The amnios is filled with amniotic fluid that cushions the embryo.
• Damage to the amnios can pose risks to fetal development.
• The amnios forms early in embryonic development from the epiblast.