| 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) |
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| 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) |
| abdominal aorta | <anatomy> The largest arterial conduit below the diaphragm. This term refers to the portion of the aorta below the diaphragm to the bifurcation into the right and left common iliac arteries. It supplies blood to the abdominal viscera, pelvic organs and lower extremities. (20 Jun 2000) |
| abdominal part of aorta | <anatomy> The largest arterial conduit below the diaphragm. This term refers to the portion of the aorta below the diaphragm to the bifurcation into the right and left common iliac arteries. It supplies blood to the abdominal viscera, pelvic organs and lower extremities. (20 Jun 2000) |
| aorta | <anatomy> The largest artery in the body which has its origin at the heart. It gives off branches to the extremities, neck and major organs for the purpose of supplying oxygenated blood. (27 Sep 1997) |
| aorta abdominalis | <anatomy> The largest arterial conduit below the diaphragm. This term refers to the portion of the aorta below the diaphragm to the bifurcation into the right and left common iliac arteries. It supplies blood to the abdominal viscera, pelvic organs and lower extremities. (20 Jun 2000) |
| aorta angusta | Congenital narrowness of aorta. (05 Mar 2000) |
| aorta ascendens | The part of the aorta prior to the aortic arch from which arise the coronary arteries. Synonym: aorta ascendens, ascending part of aorta, pars ascendens aortae. (05 Mar 2000) |
| aorta descendens | A part of the aorta, further divided into the thoracic aorta and the abdominal aorta. Synonym: pars descendens aortae, aorta descendens, descending part of aorta. (05 Mar 2000) |
| aorta, thoracic | The portion of the descending aorta proceeding from the arch of the aorta and extending to the diaphragm. (12 Dec 1998) |
| aorta thoracica | The part of the descending aorta that supplies structures as far down as the diaphragm. Synonym: pars thoracica aortae, aorta thoracica, thoracic part of aorta. (05 Mar 2000) |
| arch of the aorta | The curved portion between the ascending and descending parts of the aorta; it begins as a continuation of the ascending aorta posterior to the sternal angle, runs posteriorly and slightly to the left as it passes over the root of the left lung, and becomes the descending aorta as it reaches and begins to course along the vertebral column; it gives rise to the brachiocephalic trunk, the left common carotid and left subclavian arteries. Any member of the several pairs of arterial channels encircling the embryonic pharynx in the mesenchyme of the brachial arches; there are potentially six pairs, but in mammals the fifth pair is poorly developed or absent. The first and second pairs are functional only in very young embryos; the third pair is involved in the formation of the carotids; the fourth arch on the left is incorporated in the arch of the aorta; the sixth pair forms the proximal part of the pulmonary arteries. A series of arterial channels encircling the embryonic pharynx in the mesenchyme of the branchial arch's. There are potentially six pairs, but in mammals the fifth pair is poorly developed or absent. The first and second pairs are functional only in very young embryos; the third pair is involved in the formation of the carotids; the fourth arch on the left is incorporated in the arch of the aorta; the sixth pair forms the proximal part of the pulmonary arteries. Synonym: arcus aortae. (05 Mar 2000) |
| arteria aorta | <anatomy> The largest artery in the body which has its origin at the heart. It gives off branches to the extremities, neck and major organs for the purpose of supplying oxygenated blood. (27 Sep 1997) |