Annulus (or anulus) or annular indicates a ring- or donut-shaped area or structure. It may refer to:

Human anatomy

* ''

Anulus fibrosus disci intervertebralis An intervertebral disc (or intervertebral fibrocartilage) lies between adjacent vertebrae in the vertebral column. Each disc forms a fibrocartilaginous joint (a symphysis), to allow slight movement of the vertebrae, to act as a ligament to hold ...

'', spinal structure * Annulus of Zinn, a.k.a. annular tendon or ''anulus tendineus communis'', around the optic nerve * Annular ligament (disambiguation) * ''Digitus anularis'', a.k.a.

ring finger The ring finger, third finger, fourth finger, leech finger, or annulary is the fourth digit of the human hand, located between the middle finger and the little finger. Sometimes the term ring finger only refers to the fourth digit of a left-h ...

* ''Anulus ciliaris'', a.k.a.

ciliary body The ciliary body is a part of the eye that includes the ciliary muscle, which controls the shape of the lens, and the ciliary epithelium, which produces the aqueous humor. The aqueous humor is produced in the non-pigmented portion of the ciliar ...

* ''Anulus femoralis'', a.k.a. femoral ring * ''Anulus inguinalis superficialis'', a.k.a.

superficial inguinal ring The inguinal canals are the two passages in the anterior abdominal wall of humans and animals which in males convey the spermatic cords and in females the round ligament of the uterus. The inguinal canals are larger and more prominent in males. T ...

* ''Anulus inguinalis profundus'', a.k.a. deep inguinal ring * ''Anuli fibrosi cordis'', a.k.a. fibrous rings of heart * ''Anulus umbilicalis '', a.k.a. umbilical ring

Other

* Annulus (construction), outer gear ring in an

epicyclic gearing An epicyclic gear train (also known as a planetary gearset) consists of two gears mounted so that the center of one gear revolves around the center of the other. A carrier connects the centers of the two gears and rotates the planet and sun gea ...

* Annulus (botany), structure on fern and moss sporangia *

Annular lake An impact crater lake is a lake inside a depression caused by the impact of a meteor. It is also known as an annular lake in cases where the water body is shaped like a ring, as many impact crater lakes are. Examples One of the largest impac ...

, a ring-shaped lake caused by meteor impact * Annulus (mathematics), the shape between two concentric circles *

Annulus (mycology) An annulus is the ring-like or collar-like structure sometimes found on the stipe of some species of mushrooms. The annulus represents the remnants of the partial veil, after it has ruptured to expose the gills or other spore-producing surface. ...

, structure on mushroom *

Annulus (firestop) {{unreferenced, date=March 2015 The annulus, or annular space, is the space between a penetrant and whatever surrounds it, such as the sides of an opening or a sleeve A sleeve ( ang, slīef, a word allied to '' slip'', cf. Dutch ) is the pa ...

, site of construction issue * Annular piston, a ring-shaped piston *

Annulus (well) The annulus of an oil well or water well is any void between any piping, tubing or casing and the piping, tubing, or casing immediately surrounding it.SchlumbergeOilfield Glossary: Term 'annulus', retrieved 18 February 2010. It is named after ...

, void between concentric cylinders *

Annular blowout preventer A blowout preventer (BOP) (pronounced B-O-P, not "bop") is a specialized valve or similar mechanical device, used to seal, control and monitor oil and gas wells to prevent blowouts, the uncontrolled release of crude oil or natural gas from a ...

, device for sealing oil and gas wells *

Annulation In organic chemistry annulation (from the Latin ''anellus'' for "little ring"; occasionally annelation) is a chemical reaction in which a new ring is constructed on a molecule. : Examples are the Robinson annulation, Danheiser annulation and ce ...

, type of ring-producing chemical reaction

Human anatomy

Other

See also