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Noun, pl. opercula

1. A covering flap or lidlike structure in plants and animals, such as a gill cover. (

2. A lid or cover becoming detached at maturity by abscission, in eucalyptus (for example), a cap covering the bud and formed by fusion or cohesion of perianth parts. (

(Human Anatomy)
1. (In pregnancy), the cervical mucus plug that blocks the cervix of the uterus after conception.

2. (Brain), the part of the brain covering the insula.

3. (Dentistry), a small flap of tissue which may cover an erupting or partially erupted molar.

(Animal Biology)
1. (Animal), a structure resembling a lid or a small door that opens and closes.

2. (Fish), a flap of the bony fish covering the gills.

3. (Gastropod), a lid on the shell of some gastropods.

4. (Bird), a structure which covers the nares of some birds.

5. (Bryozoa), a lid on the orifice of some bryozoans.

6. The anterior end of the fruit fly puparium, through which the adult fly emerges.

1. Various lids and flaps pertaining to plants, algae and fungi.

Word origin: From Latin operculum “cover, lid,” from operire “to cover, close.”

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