1. A round area, organ, or band around a circular opening.
SEE: annulus
2. In chemistry, a collection of atoms chemically bound in a circle.

abdominal ring

Any of the deficiencies in the abdominal wall that forms the ends of the inguinal canal. The deep or internal inguinal ring is formed by an outpocketing of endoabdominal (transversalis) fascia; the external or superficial inguinal ring is formed by a split in the aponeurosis of the external oblique.

abdominal inguinal ring

Any of the deep or superficial openings of the inguinal canal.

benzene ring

A closed planar ring of six carbon atoms.

biofragmentable anastomosis ring

ABBR: BFR; BAR An absorbable, temporary surgical implant to join resected loops of bowel. The ring is composed of two parts polyglycolic acid (Dexon) and one part barium sulfate. It dissolves about 3 weeks after implantation when major tissue healing has occurred. The ring is easy to use. Postoperative complications may include leakage and, rarely, intestinal stricture.

Cabot rings

SEE: Cabot rings

Cannon ring

SEE: Cannon, Walter B.

capsular tension ring

A ring inserted into the capsule of the eye to maintain its shape or integrity, e.g., to compensate for zonular weakness or defects.

ciliary ring

SEE: Orbiculus ciliaris.

conjunctival ring

A narrow ring at the junction of the edge of the cornea with the conjunctiva.
SYN: SEE: anulus conjunctivae

constriction ring

A stricture of the body of the uterus; a circular area of the uterus that contracts around a part of the fetus.

cyclopentanoperhydrophenanthrene ring

The basic underlying structure of all steroid hormones.

deep inguinal ring

The opening of the inguinal canal deep inside the abdominal wall.

femoral ring

The superior aperture of the femoral canal, approx. 1 cm in diameter.

inguinal ring

The interior opening of the abdominal inguinal ring and the end of the subcutaneous inguinal ring.

Kayser-Fleischer ring

SEE: Kayser-Fleischer ring

Müller ring

SEE: Müller, Johannes P.

penile ring

A ring made of metal, plastic, or leather. When placed around the flaccid penis, it is small enough to prevent venous return. Use of the device assists in maintaining erection of the penis and in delaying orgasm.

physiologic retraction ring

SEE: retraction ring

retraction ring

A ridge sometimes felt on the uterus above the pubes, marking the line of separation between the upper contractile and lower dilatable segments of the uterus. If the ring is normal, as in a normal delivery, it is called the physiologic retraction ring; if the ring persists, as in prolonged labor, it is called the pathologic retraction ring.
SYN: SEE: Bandl contraction ring; SEE: Bandl ring

Schatzki ring

SEE: Schatzki ring

Schwalbe ring

SEE: Schwalbe, Gustav Albert

Soemmering ring

SEE: Soemmering, Samuel T. von

subcutaneous inguinal ring

SEE: Superficial inguinal ring.

superficial inguinal ring

The external/superficial opening of the inguinal canal formed from a deficiency in the external abdominal oblique muscle.
SYN: SEE: subcutaneous inguinal ring

teething ring

Any relatively soft object on which an infant may chew to relieve discomfort during the eruption of teeth. Teething rings and other teething devices small enough to be inhaled by an infant should never be used.

tonsillar ring

The almost complete ring of tonsillar tissue encircling the pharynx. It includes the palatine, lingual, and pharyngeal tonsils.

tympanic ring

A band of bone formed by three parts (squamous, petromastoid, and tympanic) that develops into the tympanic plate.

umbilical ring

The opening in the linea alba of the embryo through which the umbilical vessels pass.

vaginal ring

1. A flexible polymer impregnated with contraceptive hormones which a woman places inside her vagina and leaves in place for 21 or more days. When it is removed, withdrawal bleeding occurs. Side effects can include vaginitis or vaginal irritation. Like other forms of contraception, the ring increases a woman's risk of blood clotting. It should be avoided by smokers. It does not provide protection against sexually transmitted diseases.
2. A similar device, impregnated with menopausal hormones and used to treat hot flashes, night sweats, and other menopausal symptoms. Like other forms of menopausal hormone replacement, it increases the risk of stroke, heart attack, deep venous thrombosis, breast, and uterine cancers.

vascular ring

A congenital abnormality in which an arterial ring encircles the trachea and esophagus. This causes signs of compression of their structures. Surgery may be required to relieve the symptoms.