| os sesamoideum | A bone formed in a tendon where it passes over a joint. Synonym: os sesamoideum. (05 Mar 2000) |
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| os sphenoidale | A bone of most irregular shape occupying the base of the skull; it is described as consisting of a central portion, or body, and six processes: two greater wings, two lesser wings and two pterygoid processes; it articulates with the occipital, frontal, ethmoid, and vomer, and with the paired temporal, parietal, zygomatic, palatine and sphenoidal concha bones. Synonym: os sphenoidale, sphenoid. (05 Mar 2000) |
| os subtibiale | An inconstant bone found very rarely in the distal articular end of the tibia. (05 Mar 2000) |
| os suprasternale | One of the small ossicles occasionally found in the ligaments of the sternoclavicular articulation. Synonym: Breschet's bones, episternal bone, suprasternal bone. (05 Mar 2000) |
| os sylvii | A knob at the tip of the long limb of the incus which articulates with the stapes. Synonym: processus lenticularis incudis, lenticular apophysis, lenticular bone, orbicular bone, orbicular process, orbiculare, os orbiculare, os sylvii. (05 Mar 2000) |
| os temporale | <anatomy> A large irregular bone situated in the base and side of the skull, consisting of three parts, squamous, tympanic and petrous. The bones are distinct at birth; the petrous part contains the vestibulocochlear organ; the bone articulates with the sphenoid, parietal, occipital, and zygomatic bones, and by a synovial joint with the mandible. Synonym: os temporale. (05 Mar 2000) |
| os tibiale posterius | Os tibiale posticum, a sesamoid bone in the tendon of the tibialis posterior muscle, occasionally fused with the tuberosity of the navicular. Synonym: tibiale posticum. (05 Mar 2000) |
| os trapezium | Origin: NL, fr. Gr. A little table, an irregular four-sided figure, dim. Of a table, for; (see Tetra-) + foot, akin to foot; hence, originally, a table with four feet. See Foot. 1. <geometry> A plane figure bounded by four right lines, of which no two are parallel. 2. <anatomy> A bone of the carpus at the base of the first metacarpal, or thumb. A region on the ventral side of the brain, either just back of the pons Varolii, or, as in man, covered by the posterior extension of its transverse fibres. Source: Websters Dictionary (01 Mar 1998) |
| os trapezoideum | A bone in the distal row of the carpus; it articulates with the second metacarpal, trapezium, capitate, and scaphoid. Synonym: os trapezoideum, lesser multangular bone, os multangulum minus, trapezoid. (05 Mar 2000) |
| os triangulare | An independent ossicle sometimes present in the tarsus; usually it forms part of the talus, constituting the lateral tubercle of the posterior process. Synonym: os triangulare, triangular bone. (05 Mar 2000) |
| os tribasilare | The single bone resulting from the fusion in infancy of the occipital and temporal bones at the base of the cranial cavity. (05 Mar 2000) |
| os trigonum | An independent ossicle sometimes present in the tarsus; usually it forms part of the talus, constituting the lateral tubercle of the posterior process. Synonym: os triangulare, triangular bone. (05 Mar 2000) |
| os triquetrum | A bone on the medial (ulnar) side of the proximal row of the carpus, articulating with the lunate, pisiform, and hamate. Synonym: os triquetrum, cubital bone, os pyramidale, os triangulare, pyramidal bone, pyramidale, three-cornered bone, triquetrum. (05 Mar 2000) |
| os unguis | An irregularly rectangular thin plate, forming part of the medial wall of the orbit behind the frontal process of the maxilla; it articulates with the inferior nasal concha, ethmoid, frontal, and maxillary bones. Synonym: os lacrimale, os unguis. (05 Mar 2000) |
| os uteri externum | The vaginal opening of the uterus. Synonym: ostium uteri, mouth of the womb, opening of uterus, orificium externum uteri, os uteri externum, ostium uteri externum. (05 Mar 2000) |