| helicoid | Coiled, of a cymose inflorescence, branching repeatedly on the same side. (09 Oct 1997) |
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| helicoid choroidopathy | Bilateral acquired abnormality of retinal pigment epithelium and choroid in which irregular multiple progressive swelling is followed by atrophic scars in linear patterns. Synonym: helicoid choroidopathy, serpiginous choroidopathy. (05 Mar 2000) |
| helicoid ginglymus | A synovial joint in which a section of a cylinder of one bone fits into a corresponding cavity on the other, as in the proximal radioulnar joint. Synonym: articulatio trochoidea, helicoid ginglymus, lateral ginglymus, rotary joint, rotatory joint, trochoid articulation, trochoid joint. (05 Mar 2000) |
| helicoidal cell wall | Type of plant cell wall in which each wall layer contains parallel microfibrils, but in which the orientation of the microfibrils changes by a fixed angle from one layer to the next. Gives a characteristic herringbone pattern in transmission electron microscopy. A similar architecture of fibrillar material is seen in some insect exoskeletons. (18 Nov 1997) |