operculum

• 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

• 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

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

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

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