The innermost membrane of the fetal membranes of reptiles, birds, and mammals; the sac in which the embryo is suspended.
A microscopic double layer of lipids and proteins forming the boundary of cells or organelles.
A flexible or semiflexible covering or waterproofing whose primary function is to exclude water.
A mechanical, thin, flat flexible part that can deform or vibrate when excited by an external force.
A piece of parchment forming part of a roll.