Operculum

Operculum may refer to:

Human biology

 * Operculum (brain), the part of the brain covering the insula
 * Operculum (dentistry), a small flap of tissue which may cover an erupting or partially erupted molar
 * Cervical mucus plug, the cervical mucus plug that blocks the cervix of the uterus after conception

Animal biology

 * Operculum (animal), a structure resembling a lid or a small door that opens and closes
 * Operculum (bird), a structure which covers the nares of some birds
 * Operculum (bryozoa), a lid on the orifice of some bryozoans
 * Operculum (fish), a flap covering the gills of bony fish
 * Operculum (gastropod), a sort of trapdoor used to close the aperture of some snails
 * Operculum papillare, the iris found in the eyes of elasmobranchs (skates, sharks, and rays)
 * The anterior end of the puparium in some insects, through which the adult emerges; for example the wasp Stenogastrinae

Botany

 * Operculum (botany), various lids and flaps pertaining to plants, algae, and fungi