| vascular circle | The circle around the mouth formed by the inferior and superior labial arteries. Synonym: areolar venous plexus. (05 Mar 2000) |
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| vascular circle of optic nerve | <anatomy, nerve> A network of branches of the short ciliary arteries on the sclera around the point of entrance of the optic nerve. Synonym: circulus vasculosus nervi optici, circulus arteriosus halleri, circulus zinnii, Haller's circle, Zinn's corona, Zinn's vascular circle. (05 Mar 2000) |
| Ramsden circle | <microscopy> The circular spot of light formed at that distance above the eyepiece where the chief image forming rays cross, the back focal plane of the eyepiece. The objective back focal plane is in conjugate focus in this same plane. In visual microscopy, the point where the pupil of the eye is placed. (05 Aug 1998) |
| venous circle of mammary gland | areolar venous plexus |
| Carus' circle | An imaginary curved line obtained from a mathematical formula, supposed to indicate the outlet of the pelvic canal. Synonym: Carus' circle. (05 Mar 2000) |
| vicious circle | The mutually accelerating action of two independent diseases or phenomena, or of a primary and secondary affection, the passage of food, after a gastroenterostomy, from the artificial opening through the intestinal loop by antiperistaltic action and back into the stomach again by the pyloric orifice, or the reverse. (05 Mar 2000) |
| Ridley's circle | Dural venous formation which surrounds the hypophysis, composed of right and left cavernous sinuses and the intercavernous sinuses. Synonym: circulus venosus ridleyi, Ridley's circle. A venous sinus at the periphery of the placenta. Synonym: sinus venosus sclerae. (05 Mar 2000) |
| rolling circle | A mechanism for the replication of circular DNA. (05 Mar 2000) |
| rolling circle mechanism | <molecular biology> A mechanism of DNA replication in many viral DNAs, in bacterial f factors during mating and of certain DNAs in gene amplification in eukaryotes. DNA synthesis starts with a cut in the + strand at the replication origin, the 5' end rolls out and replication starts at the 3' side of the cut around the intact circular DNA strand. Replication of the 5' end (tail) takes place by the formation of Okazaki fragments. (18 Nov 1997) |
| circle | 1. A ring-shaped structure or group of structures. 2. A line or process with every point equidistant from the centre. Synonym: circellus. Origin: L. Circulus (05 Mar 2000) |
| circle absorption anaesthesia | Inhalation anaesthesia in which a circuit with carbon dioxide absorbent is used for complete (closed) or partial (saemiclosed) rebreathing of exhaled gases. (05 Mar 2000) |
| closed circle | A circuit for administration of an inhalation anaesthetic in which there is complete rebreathing with carbon dioxide absorption. (05 Mar 2000) |
| condenser circle | <microscopy> The image of the aperture iris diaphragm of the substage condenser as seen in the back focal plane of the objective. (05 Aug 1998) |
| Haller's circle | <anatomy, nerve> A network of branches of the short ciliary arteries on the sclera around the point of entrance of the optic nerve. Synonym: circulus vasculosus nervi optici, circulus arteriosus halleri, circulus zinnii, Haller's circle, Zinn's corona, Zinn's vascular circle. (05 Mar 2000) |
| semi-closed circle | A circuit for administration of an inhalation anaesthetic in which partial rebreathing with carbon dioxide absorption is combined with loss from the circuit of a portion of respired gases through valves. (05 Mar 2000) |