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 t ...

'', spinal structure *

Annulus of Zinn The common tendinous ring, also known as the annulus of Zinn, or annular tendon, is a ring of fibrous tissue surrounding the optic nerve at its entrance at the apex of the orbit. It is the common origin of the four recti muscles of the group of ex ...

, a.k.a. annular tendon or ''anulus tendineus communis'', around the optic nerve *

Annular ligament (disambiguation) Annular ligament may refer to: * Zona orbicularis, Annular ligament of femur * Annular ligaments of fingers * Annular ligament of radius *Annular ligament of stapes (also known as the stapediovestibular joint) * Annular ligaments of trachea * Annul ...

* ''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-han ...

* ''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 The femoral ring is the opening at the proximal, abdominal end of the femoral canal, and represents the (superiorly directed/oriented) base of the conically-shaped femoral canal. The femoral ring is oval-shaped, with its long diameter being direc ...

* ''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. Th ...

* ''Anulus inguinalis profundus'', a.k.a.

deep 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. ...

* ''Anuli fibrosi cordis'', a.k.a.

fibrous rings of heart In cardiology, the cardiac skeleton, also known as the fibrous skeleton of the heart, is a high-density homogeneous structure of connective tissue that forms and anchors the valves of the heart, and influences the forces exerted by and through th ...

* ''Anulus umbilicalis '', a.k.a.

umbilical ring The umbilical ring is a dense fibrous ring surrounding the Navel, umbilicus at birth. At about the sixth week of embryological development, the midgut herniates through the umbilical ring; six weeks later it returns to the abdominal cavity and rot ...

Other

Annulus (construction) Annulus (or anulus) or annular indicates a ring- or donut-shaped area or structure. It may refer to: Human anatomy * ''Anulus fibrosus disci intervertebralis'', spinal structure * Annulus of Zinn, a.k.a. annular tendon or ''anulus tendineus com ...

, 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) {{Short description, A ring of specialized cells on the sporangium An annulus in botany is an arc or a ring of specialized cells on the sporangium. These cells are arranged in a single row, and are associated with the release or dispersal of spores. ...

, 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) In mathematics, an annulus (plural annuli or annuluses) is the region between two concentric circles. Informally, it is shaped like a ring or a hardware washer. The word "annulus" is borrowed from the Latin word ''anulus'' or ''annulus'' mean ...

, 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 part ...

, 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 w ...

, 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 cert ...

, type of ring-producing chemical reaction

Human anatomy

Other

See also