| ORANS | Oak Ridge Analytical System |
|---|---|
| ORNL | Oak Ridge National Laboratory |
| SAR | scatter/air ratio; seasonal allergic rhinitis; sexual attitude reassessment; slowly adapting recepto... |
| TRC | tanned red cell; therapeutic residential center; total renin concentration; total respiratory conduc... |
| 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 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) |
| alveolar ridge | That portion of bone in either the maxilla or the mandible which surrounds and supports the teeth. (12 Dec 1998) |
| alveolar ridge augmentation | Preprosthetic surgery involving rib, cartilage, or iliac crest bone grafts, usually autologous, or synthetic implants for rebuilding the alveolar ridge. (12 Dec 1998) |
| apical ectodermal ridge | The layer of surface ectodermal cells at the apex of the embryonic limb bud; considered to exert an inductive influence on the condensation of underlying mesenchyme. (05 Mar 2000) |
| basal ridge | That portion of bone in either the maxilla or the mandible which surrounds and supports the teeth. (12 Dec 1998) |
| buccocervical ridge | A convexity within the cervical third of the buccal surface of molars. (05 Mar 2000) |
| buccogingival ridge | A distinct ridge on the buccal surface of a deciduous molar tooth, approximately 1.5 mm from the crown-root junction. (05 Mar 2000) |
| bulbar ridge | One of two spiral subendocardial thickenings in the embryonic bulbus cordis; when they fuse, they divide the bulbus into the aorta and pulmonary artery. (05 Mar 2000) |
| bulboventricular ridge | An elevation on the inner surface of the embryonic heart at four to five weeks; it indicates the division between the developing ventricles and the bulbus cordis. (05 Mar 2000) |
| palatine ridge | A rather narrow, low elevation in the centre of the hard palate that extends from the incisive papilla posteriorly over the entire length of the mucosa of the hard palate. Synonym: raphe palati, palatine ridge. (05 Mar 2000) |
| ganglion ridge | A group of embryonic cells that separate from the neural plate during neurulation and migrate to give several different lineages of adult cells: the spinal and autonomic ganglia, the glial cells of the peripheral nervous system and nonneuronal cells, such as chromaffin cells, melanocytes and some haemopoietic cells. (18 Nov 1997) |
| mammary ridge | Bandlike thickening of ectoderm in the embryo extending on either side from just below the axilla to the inguinal region; in human embryos, the mammary glands arise from primordia in the thoracic part of the ridge, the balance of the ridge disappearing; in some lower mammals which give birth to a litter of young, several milk glands develop along these lines. Synonym: mammary fold, milk line, milk ridge. (05 Mar 2000) |