| benzene ring | The closed-chain arrangement of the carbon and hydrogen atoms in the benzene molecule. See: cyclic compound. (05 Mar 2000) |
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| Bickel's ring | The broken ring of lymphoid tissue, formed of the lingual, faucial, and pharyngeal tonsils. Synonym: Bickel's ring, tonsillar ring, Waldeyer's throat ring. (05 Mar 2000) |
| Cabot's ring bodies | Ring-shaped or figure-of-eight structures that stain red with Wright's stain, found in red blood cells in severe anaemias, possibly a remnant of the nuclear membrane; a form of basophilic degenerative process. (05 Mar 2000) |
| Cannon's ring | The location in the mid-transverse colon at which innervation by superior and inferior mesenteric plexuses overlap at the junction of the primitive midgut and hindgut, frequently resulting in narrowing evident on barium enema. See: Cannon's ring. Synonym: Cannon's ring. (05 Mar 2000) |
| carcinoma, signet ring cell | A highly malignant, mucus-secreting tumour in which the mucus-secreting cells are anaplastic and appear rounded, with the nucleus displaced to one side by a globule of mucus in the cytoplasm. (12 Dec 1998) |
| cardiac lymphatic ring | A group of lymph nodes surrounding the cardia of the stomach. Synonym: annulus lymphaticus cardiae, cardiac lymphatic ring. (05 Mar 2000) |
| vascular ring | Anomalous arteries (aortic arches) congenitally encircling the trachea and oesophagus, at times producing pressure symptoms. (05 Mar 2000) |
| marginal ring ulcer of cornea | A slowly advancing intermittent ulcer involving the circumference of the corneal margin. (05 Mar 2000) |
| casting ring | A metal tube in which a refractory mold is made for casting metal dental restorations or appliances. Synonym: casting flask, casting ring. (05 Mar 2000) |
| Vieussens' ring | A muscular ring surrounding the fossa ovalis in the wall of the right atrium of the heart. Synonym: annulus ovalis, margin of fossa ovalis, Vieussens' annulus, Vieussens' isthmus, Vieussens' limbus, Vieussens' ring. (05 Mar 2000) |
| glaucomatous ring | A yellowish white ring surrounding the optic disk, indicating atrophy of the choroid in glaucoma. Synonym: glaucomatous ring. A halo surrounding lights, caused by corneal oedema in glaucoma. Synonym: rainbow symptom. (05 Mar 2000) |
| pathologic retraction ring | A constriction located at the junction of the thinned lower uterine segment with the thick retracted upper uterine segment, resulting from obstructed labour; this is one of the classic signs of threatened rupture of the uterus. Synonym: Bandl's ring, Baudelocque's uterine circle, Scanzoni's second os. (05 Mar 2000) |
| medial crus of the superficial inguinal ring | Portion of the external oblique aponeurosis which passes medial to the superficial inguinal ring forming the medial boundary of the ring. Synonym: crus mediale annuli inguinalis superficialis. (05 Mar 2000) |
| Vossius' lenticular ring | A ring-shaped opacity found on the anterior lens capsule after contusion of the eye, due to pigment and blood. (05 Mar 2000) |
| Graefenberg ring | An obsolete term for a silver or silkworm gut ring designed for insertion into the uterine cavity as a means of contraception. (05 Mar 2000) |