In the human embryo, the earliest stages of the formation of the amnion have not been observed; in the youngest embryo which has been studied the amnion was already present as a closed sac, and appears in the inner cell-mass as a cavity.
Najraniji stadiji oblikovanja amniona kod čovječjeg zametka još nisu bili promatrani; kod najmlađeg zametka čiji se amnion proučavao, amnion je bio već bio prisutan kao zatvorena vreća i nalazio se u unutarnjoj staničnoj masi kao šupljina.