membrana

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A membrane, especially a biomembrane.

Pl. membranae [L.] membrane.

• m. granulosa — the layer of small, actively mitotic cells in the wall of the ovarian follicle.
• m. nictitans — a fold of conjunctiva supported by a T-shaped cartilage and attached at the medial canthus of the eye; the so-called third eyelid in animals. In most animal species, it moves across the cornea when the upper and lower eyelids are closed. Prolapse of the membrane so that it is held in position halfway across the eye when the eyelids are open is a nonspecific sign of ill health in cats. Spasm of the membrane so that it is drawn smartly across the eye with a slow return to a normal position is a diagnostic sign of tetanus in all species. See also nictitating membrane, third eyelid.