The<unk>  is the sac in which the fetus develops.
Some sources consider it to be equivalent to the amnion,, while other sources consider it to consist of the amnion and the chorion.
It is also called the<unk>  bubble because of its resemblance to a bubble.
When in the light, the<unk>  is shiny and very smooth, but too tough to pierce through.
Amniotic sac
Yolk sac
Fallopian tube
Spermatic cord
Endometrium
Umbilical cord
Decidua
Corpus luteum