| primitive pit | The depression in the primitive node that serves to connect the notochordal canal with the surface ectoderm and the yolk sac. These connections are referred to as the neurenteric canal. (05 Mar 2000) |
|---|---|
| primitive reticular cell | A cell with processes making contact with those of other similar cell's to form a cellular network; along with the network of reticular fibres, the reticular cell's form the stroma of bone marrow and lymphatic tissues. (05 Mar 2000) |
| primitive ridge | One of the paired ridge's on either side of the primitive groove. (05 Mar 2000) |
| primitive streak | An ectodermal ridge in the midline at the caudal end of the embryonic disk from which arises the intraembryonic mesoderm; achieved by inward and then lateral migration of cells; in human embryos, it appears on day 15 and gives a cephalocaudal axis to the developing embryo. Synonym: germinal streak. (05 Mar 2000) |
| neuroectodermal tumour, primitive | A malignant brain tumour sharing common features and biologic properties with medulloblastoma. Some pathologists and clinicians use the terms interchangeably: they both can disseminate throughout the nervous system and, in some cases, systemically. most lesions arise from the posterior fossa in children under five years of age. The tumour often produces hydrocephalus and symptoms of increased intracranial pressure. Papilledema is often present. (12 Dec 1998) |
| acromioclavicular dislocation | <orthopaedics> Disruption of the normal articulation between the acromion process and the clavicle. The acromioclavicular joint (AC joint) is normally stabilised by several ligaments that can be torn in the process of dislocating the AC joint). See: acromioclavicular sprain. (27 Sep 1997) |
| patellar dislocation | <radiology> most common in young girls, (genu valgum, patella alta, quad mm deficiency more in girls), lateral dislocation, spontaneous reduction, recurrent dislocation, fracture associated in 5-10% (12 Dec 1998) |
| perilunar dislocation | Dislocation of carpal bones around the lunate, which remains in relation to the radius; distinguish from dislocation of lunate, Kienbock's dislocation. (05 Mar 2000) |
| perilunate dislocation | <radiology> Lunate remains aligned with radius, capitate dislocates (usually posteriorly), more common than lunate dislocation (radial-lunate ligaments stronger than lunate-capitate ligaments), associated with scaphoid fractures (75%) = transscaphoid perilunate dislocation (12 Dec 1998) |
| chopart fracture-dislocation | <radiology> A fracture-dislocation occuring through the hindfoot-midfoot joint (i.e., tarsonavicular and calcaneocuboid joints) (12 Dec 1998) |
| closed dislocation | A dislocation not complicated by an external wound. Synonym: simple dislocation. (05 Mar 2000) |
| compound dislocation | Synonym: open dislocation. (05 Mar 2000) |
| congenital hip dislocation | A malformation of the hip joint that is present at birth. Genetic factors likely play a role in this disorder. Features include hip dislocation, asymmetry of leg positions, asymmetric fat folds and diminished movement on the affected side. Some children will exhibit little or no features and must be diagnosed by physical examination of the hip joints. (27 Sep 1997) |
| wrist dislocation | <radiology> 10% of all carpal injuries due to fall on outstretched hand, perilunate dislocation (more common), lunate dislocation (12 Dec 1998) |
| hip dislocation | <radiology> Usually posterior, hip flexed, knee hits dashboard during deceleration, superior migration of femoral head, with or without acetabular fracture (12 Dec 1998) |