| Waldeyer's throat 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) |
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| common tendinous ring | A fibrous ring that surrounds the optic canal and the medial part of the superior orbital fissure; it gives origin to the four rectus muscles of the eye and is partially fused with the sheath of the optic nerve. Synonym: annulus tendineus communis, Zinn's ligament, Zinn's ring, Zinn's tendon. (05 Mar 2000) |
| M ring | <biology, microbiology> Innermost (motor) ring of the bacterial flagellar base, located in the outer leaflet of the plasma membrane. It is this ring that is linked to the hook region (and thus to the flagellum itself) and that rotates. Composed of 16 or 17 subunits (one more or less than the S ring). (13 Nov 1997) |
| wimberger ring | <radiology> Dense rim of demineralised epiphysis seen in scurvy (12 Dec 1998) |
| conjunctival ring | A narrow ring at the junction of the periphery of the cornea with the conjunctiva. Synonym: annulus conjunctivae. (05 Mar 2000) |
| constriction ring | The equatorial ring of microfilaments that diminishes in diameter probably both by contraction and disassembly as cytokinesis proceeds. (18 Nov 1997) |
| contractile ring | The equatorial ring of microfilaments that diminishes in diameter probably both by contraction and disassembly as cytokinesis proceeds. (18 Nov 1997) |
| polar ring | A thickened, electron-dense ring at the anterior end of certain stages of the Apicomplexa; part of the apical complex characteristic of these sporozoans. (05 Mar 2000) |
| crural ring | The superior opening of the femoral canal, bounded anteriorly by the inguinal ligament, posteriorly by the pectineus muscle, medially by the lacunar ligament, and laterally by the femoral vein. Passageway by which many lymphatics from lower limb pass to abdomen. Accommodates enlargement of femoral vein in Valsalva manoeuvre. Often occupied by a lymph node (Cloquet's) and is the site of femoral hernias. Synonym: annulus femoralis, crural ring. (05 Mar 2000) |
| P ring | <microbiology> One of the bushes at the base of the flagellum of gram-negative bacteria, anchoring it in the peptidoglycan layer of the cells wall. Lies below the L ring. (18 Nov 1997) |
| schatzki ring | <radiology> B ring of distal oesophagus, squamo-columnar junction, with or without hiatus hernia, intemittent symptoms if 13-20 mm, steakhouse syndrome, Treatment: balloon or bougie see: oesophageal webs and rings (12 Dec 1998) |
| schatzki's ring | A congenital anatomic narrowing in the lower 1/3 of the oesophagus that is the result of inappropriate embryological development of the oesophagus. Symptoms include difficulty swallowing and chest pain (under the sternum). Treatment involves the use of a fibreoptic endoscope using a dilator to open up the narrowed segment of the oesophagus. (27 Sep 1997) |
| heterocyclic compounds, 1-ring | A class of organic compounds containing a ring structure made up of more than one kind of atom, usually carbon plus another atom. The ring structure can be aromatic or nonaromatic. (12 Dec 1998) |
| heterocyclic compounds, 2-ring | A class of organic compounds containing two ring structures, one of which is made up of more than one kind of atom, usually carbon plus another atom. The heterocycle may be either aromatic or nonaromatic. (12 Dec 1998) |
| heterocyclic compounds, 3-ring | A class of organic compounds containing three ring structures, one of which is made up of more than one kind of atom, usually carbon plus another atom. The heterocycle may be either aromatic or nonaromatic (12 Dec 1998) |