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Opened amniotic sac in a 20-day-old and 2 mm large human embryo. The amniotic cavity surrounds the embryo, on which the primitive stripes and neural groove are clearly recognizable.
Translation of the inscription:
Yolk-sac = yolk sac
Neural groove = neural groove
Primitive streak = primitive streak
Neurenteric canal = neurenteric canal
body stalk = stalk
Fetus of a cat in the amniotic sac from its mother's uterus .
1 umbilical cord
2 amnion
3 allantois
4 yolk sac
5 marginal hematoma
6 the maternal part of the placenta
Scheme of a chicken egg
(9th day of development)

The amnion ( ancient Greek ἀμνίον amníon , German 'that belongs to the lamb' ), also called sheep skin , is the thin, transparent, vascularless inner egg skin and thus part of the amniotic sac containing the fetus in amniotes such as reptiles, birds and mammals. With them, the chorion ( villi skin ) forms the middle and the decidua (sieve skin) the outer membrane.

The cavity enclosed by the amnion, the amnion cavity , enlarges very quickly during the embryonic development and surrounds the human embryo with its umbilical cord on all sides as early as the fourth week of pregnancy . The fruit side, single-layer epithelial amnion secretes amniotic fluid as amniotic fluid into the amniotic sac. To win it for an examination requires an amniocentesis .



Amniotic membranes are transplanted to treat surface defects in the conjunctiva and cornea of the eye.

See also


  • Monika Kressin, Bertram Schnorr: Embryology of Pets. 5th edition. Enke-Verlag, Stuttgart 2006, ISBN 3-8304-1061-1 .