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 See also Dehiscence (botany), the opening of a plant structure, such as a fruit, anther, or sporangium, to release its contents