| third peroneal muscle | <anatomy, muscle> Origin, in common with musculus extensor digitorum longus; insertion, dorsum of base of fifth metatarsal bone; nerve supply, deep branch of peroneal; action, assists in dorsiflexion and eversion of foot. Synonym: musculus fibularis tertius, musculus peroneus tertius, third peroneal muscle. (05 Mar 2000) |
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| third sound | Occurs in early diastole and corresponds with the end of the first phase of rapid ventricular filling; normal in children and younger people but abnormal in others. Synonym: third sound. (05 Mar 2000) |
| third stage of labour | The part of labour from the birth of the baby until the placenta (afterbirth) and foetal membranes are delivered. The third stage of labour is also called the placental stage. (12 Dec 1998) |
| third temporal convolution | A sagittal convolution on the inferolateral border of the temporal lobe of the cerebrum, separated from the middle temporal gyrus by the inferior temporal sulcus. On the inferior surface of the temporal lobe it is separated from the medial occipitotemporal gyrus by the occipitotemporal sulcus. It includes the lateral occipitotemporal gyrus. Synonym: gyrus temporalis inferior, inferior temporal convolution, third temporal convolution. (05 Mar 2000) |
| third tonsil | A collection of more or less closely aggregated lymphoid nodules on the posterior wall and roof of the nasopharynx, the hypertrophy of which constitutes the morbid condition called adenoids. Synonym: tonsilla pharyngealis, tonsilla adenoidea, Luschka's gland, Luschka's tonsil, third tonsil. (05 Mar 2000) |
| third trochanter | An occasional process at the proximal end of the lateral lip of the linea aspera of the femur, about on a level with the lesser trochanter, giving insertion to the greater part of the gluteus maximus muscle. See: gluteal tuberosity. (05 Mar 2000) |
| third ventricle | A narrow, vertically oriented, irregularly quadrilateral cavity in the midplane, extending from the lamina terminalis to the rostral opening of the mesencephalic aqueduct. This ventricle communicates at its rostrodorsal corner with each of the two lateral ventricles through the left and right interventricular foramen of Monro. Its narrow roof is formed by the tela choroidea which is attached on either side to the tenia thalami; its lateral wall by the medial surface of the thalamus and, below the hypothalamic sulcus, by the hypothalamus which also forms its floor. In lateral profile, the third ventricle exhibits a number of recesses: in its floor, from before backward, 1) the preoptic recess in the acute angle between the base of the lamina terminalis and the dorsum of the optic chiasm, 2) the infundibular recess extending ventrally into the infundibulum but (in humans) not into the hypophysial stalk, and 3) the mamillary or inframamillary recess caused by the protrusion of the mamillary bodies into the ventricle. From its dorsocaudal corner, the pineal recess extends caudally into the pineal stalk. Synonym: ventriculus tertius, diacele, ventricle of diencephalon. (05 Mar 2000) |
| third ventriculostomy | An operation to establish an opening from the third ventricle to the prechiasmal and interpeduncular cisterns (Stookey-Scarff operation) or from the third ventricle to the interpeduncular cistern (Dandy operation). (05 Mar 2000) |
| bone within a bone | <radiology> STOP heavy metal, S: sickle cell disease, T: Thorotrast, O: osteopetrosis, P: Paget's disease, heavy metals, hypervitaminosis D (12 Dec 1998) |
| acute reflex bone atrophy | Atrophy of bones, commonly of the carpal or tarsal bones, following a slight injury such as a sprain. See: causalgia, reflex sympathetic dystrophy. Synonym: acute reflex bone atrophy, posttraumatic osteoporosis, Sudeck's syndrome. Origin: L. English sweat (05 Mar 2000) |
| air-bone gap | The difference between the threshold for hearing acuity by bone conduction and by air conduction. (05 Mar 2000) |
| Albrecht's bone | A small bone between the basioccipital and basisphenoid. (05 Mar 2000) |
| allogeneic bone marrow transplant | <haematology, procedure> A bone marrow transplant using marrow collected from a matched healthy donor, usually a brother or sister. The risks associated with the transplant increase with age and 50 years of age is generally regarded as the upper limit. (13 Nov 1997) |
| alveolar bone | That portion of bone in either the maxilla or the mandible which surrounds and supports the teeth. (12 Dec 1998) |
| alveolar bone loss | The resorption of bone in the supporting structures of the maxilla or mandible as a result of periodontal disease. (12 Dec 1998) |