| helix (snails) | A genus of chiefly eurasian and african land snails including the principal edible snails as well as several pests of cultivated plants. (12 Dec 1998) |
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| smaller muscle of helix | <anatomy> A band of oblique fibres covering the crus of the helix of the auricle. Synonym: musculus helicis minor, smaller muscle of helix. (05 Mar 2000) |
| DNA helix | The helical structure assumed by two strands of deoxyribonucleic acid, held together throughout their length by hydrogen bonds between bases on opposite strands, referred to as Watson-Crick base pairing. See: base pair. Synonym: DNA helix, double helix, twin helix. (05 Mar 2000) |
| double helix | <molecular biology> Conformation or shape that two linear strands of DNA assume when bonded together and become twisted into a helix. (10 Nov 1998) |
| tail of helix | A flattened process terminating the cartilage of the helix of the ear, posteriorly and inferiorly. Synonym: cauda helicis. (05 Mar 2000) |
| triple helix | The superhelix formed (right-handed) from three individual collagen helices (each being left-handed). (05 Mar 2000) |
| twin helix | The helical structure assumed by two strands of deoxyribonucleic acid, held together throughout their length by hydrogen bonds between bases on opposite strands, referred to as Watson-Crick base pairing. See: base pair. Synonym: DNA helix, double helix, twin helix. (05 Mar 2000) |
| 3.613 helix | The helical (commonly right-handed) form present in many proteins, deduced by Pauling and Corey from X-ray diffraction studies of proteins such as alpha-keratin; the helix is stabilised by hydrogen bonds between, e.g., ==C==O and HN== groups (symbolised by the centre dot in ==CO-HN==) of different eupeptide bonds. In a true a helix, there are 3.6 amino acid residues per turn of the helix. Synonym: 3.613 helix, Pauling-Corey helix. Collagen helix, an extended left-handed helix resulting from the high levels of glycine, l-proline, and l-hydroxyproline present in the collagens. There are 3.3 amino acids per turn of the helix. Three of those left-handed helices form a triple superhelix that is right-handed. (05 Mar 2000) |
| large muscle of helix | <anatomy> A narrow band of muscular fibres on the anterior border of the helix of the auricle arising from the spine and inserted at the point where the helix becomes transverse. Synonym: musculus helicis major, large muscle of helix. (05 Mar 2000) |
| fossa of helix | 1. The longitudinal furrow between the helix and the antihelix of the auricle. Synonym: fossa of helix, scaphoid fossa. 2. Obsolete term for scaphoid fossa. Origin: L. Fr. G. Skaphe, skiff (05 Mar 2000) |
| limb of helix | A transverse ridge continuing backward from the helix of the auricle, dividing the concha into an upper portion (cymba) and a lower portion (cavity of concha). Synonym: crus helicis, crista helicis, limb of helix. (05 Mar 2000) |
| alar spine | A posterior and downward projection from the greater wing of the sphenoid bone on either side, located posterolateral to the foramen spinosum, so-named for its proximity to the sphenoidal spine; gives attachment to the sphenomandibular ligament. Synonym: processus spinosus, spina ossis sphenoidalis, alar spine, angular spine, spina angularis, spinous process. (05 Mar 2000) |
| angular spine | A posterior and downward projection from the greater wing of the sphenoid bone on either side, located posterolateral to the foramen spinosum, so-named for its proximity to the sphenoidal spine; gives attachment to the sphenomandibular ligament. Synonym: processus spinosus, spina ossis sphenoidalis, alar spine, angular spine, spina angularis, spinous process. (05 Mar 2000) |
| anterior inferior iliac spine | Spine on the anterior border of the ilium between the anterior superior iliac spine and the acetabulum; site of origin for the direct head of the rectus femoris muscle. Synonym: spina iliaca anterior inferior. (05 Mar 2000) |
| anterior nasal spine | A pointed projection at the anterior extremity of the intermaxillary suture; the tip, as seen on a lateral cephalometric radiograph, is used as a cephalometric landmark. Synonym: spina nasalis anterior. (05 Mar 2000) |