| C4 | fourth cervical nerve; fourth cervical vertebra; fourth component of complement |
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| CIV | fourth cranial nerve |
| C5 | fifth cervical nerve; fifth cervical vertebra; fifth component of complement |
| CV | fifth cranial nerve |
| C6 | sixth cervical nerve; sixth cervical vertebra; sixth component of complement |
| tracheal ring | The 16 to 20 incomplete rings of hyaline cartilage forming the skeleton of the trachea; the rings are deficient posteriorly for from one-fifth to one-third of their circumference. Synonym: cartilagines tracheales, tracheal ring. (05 Mar 2000) |
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| tympanic ring | In the foetus, a more or less complete bony ring at the medial end of the cartilaginous external acoustic meatus, to which is attached the tympanic membrane. Synonym: annulus tympanicus, tympanic bone. (05 Mar 2000) |
| external inguinal ring | The slit-like opening in the aponeurosis of the external oblique muscle of the abdominal wall through which the spermatic cord (round ligament in the female) and inguinal hernias emerge from the inguinal canal. See: aponeurosis of external abdominal oblique muscle. Synonym: annulus inguinalis superficialis, external inguinal ring, subcutaneous ring. (05 Mar 2000) |
| UDPglucose-flavonol-ring-B-O-glucosyltransferase | <enzyme> Transfers glucose from udpg to positions 2' or 5' of partially methylated flavonols Registry number: EC 2.4.1.- Synonym: flavonol-ring-b o-glucosyltransferase, flavonol rbo glucosyltransferase, flavonol ring-beta-o-glucosyltransferase (26 Jun 1999) |
| Kayser-Fleischer ring | A greenish yellow pigmented ring encircling the cornea just within the corneoscleral margin, seen in hepatolenticular degeneration, due to copper deposited in Descemet's membrane. Synonym: Fleischer-Strumpell ring. (05 Mar 2000) |
| umbilical ring | An opening in the linea alba through which pass the umbilical vessels in the foetus; in young embryos it is relatively nearer to the pubis, but gradually ascends to the centre of the abdomen; it is closed in the adult, its site being indicated by the umbilicus or navel. Synonym: annulus umbilicalis, canalis umbilicalis. (05 Mar 2000) |
| Zinn's 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) |
| femoral 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) |
| fibrocartilaginous ring | Of tympanic membrane, the thickened portion of the circumference of the tympanic membrane that is fixed in the tympanic sulcus. Synonym: annulus fibrocartilagineus membranae tympani, Gerlach's annular tendon. (05 Mar 2000) |
| fibrous ring | One of four fibrous rings that surround atrioventricular and arterial orifices of the heart, providing attachment for the valve leaflets and maintaining patency of the orifice. As part of the fibrous skeleton of the heart, the fibrous rings also provide origin and insertion for the myocardium. Synonym: annulus fibrosus cordis, annulus fibrosus, coronary tendon, fibrous ring, Lower's ring. (05 Mar 2000) |
| fibrous ring of heart | One of four fibrous rings that surround atrioventricular and arterial orifices of the heart, providing attachment for the valve leaflets and maintaining patency of the orifice. As part of the fibrous skeleton of the heart, the fibrous rings also provide origin and insertion for the myocardium. Synonym: annulus fibrosus cordis, annulus fibrosus, coronary tendon, fibrous ring, Lower's ring. (05 Mar 2000) |
| fibrous ring of intervertebral disc | The ring of fibrocartilage and fibrous tissue forming the circumference of the intervertebral disc; surrounds the nucleus pulposus, which is prone to herniation when the annulus fibrosus is compromised. Synonym: annulus fibrosus disci intervertebralis, annulus fibrosus, fibrous ring of intervertebral disc, fibrous ring. (05 Mar 2000) |
| Fleischer's ring | An incomplete ring often present at the base of the keratoconus cone; it may be yellow or greenish from deposition of haemosiderin. (05 Mar 2000) |
| Fleischer-Strumpell ring | A greenish yellow pigmented ring encircling the cornea just within the corneoscleral margin, seen in hepatolenticular degeneration, due to copper deposited in Descemet's membrane. Synonym: Fleischer-Strumpell ring. (05 Mar 2000) |
| Flieringa's ring | A stainless steel ring sutured to the sclera to prevent collapse of the globe in difficult intraocular operations. (05 Mar 2000) |