| LOT | lateral olfactory tract; left occipitotransverse [fetal position] |
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| LST | lateral spinothalamic tract; left sacrotransverse [fetal position]; life-sustaining treatment |
| LVST | lateral vestibulospinal tract |
| ALS | acute lateral sclerosis; advanced life support; afferent loop syndrome; amyotrophic lateral sclerosi... |
| LGN | lateral geniculate nucleus; lateral glomerulonephritis |
| medullary membrane | <anatomy> The layer of vascular connective tissue lining the medullary cavities of bone. Origin: NL, fr. Gr. + a bone. Source: Websters Dictionary (01 Mar 1998) |
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| medullary nephrocalcinosis | <radiology> Primary hyperparathyroidism, renal tubular acidosis more than 70%, medullary sponge kidney, hypercalcaemia, hypercalcuria, sarcoidosis, bony metastases, Paget's disease, hypervitaminosis D, milk-alkali syndrome, Williams syndrome (in kids), idiopathic, oxalosis (with or without completely opaque kidneys; younger age) see also: renal calcification (12 Dec 1998) |
| medullary plate | <embryology> A region of embryonic ectodermal cells, called neuroectoderm, that lie directly above the notochord. During neurulation, they change shape, so as to produce an infolding of the neural plate (the neural fold) that then seals to form the neural tube. (04 Jul 1999) |
| medullary pyramid | One of a number of pyramidal masses seen on longitudinal section of the kidney; collectively, they constitute the renal medulla, and contain part of the secreting tubules and the collecting tubules. Synonym: pyramis renalis, malpighian pyramid, medullary pyramid. (05 Mar 2000) |
| medullary ray | The centre of the renal lobule, which has the shape of a small, steep pyramid, consisting of straight tubular parts; these may be either ascending or descending limbs of the nephronic loop or collecting tubules. Synonym: pars radiata lobuli corticalis renis, Ferrein's pyramid, processus ferreini. (05 Mar 2000) |
| medullary sarcoma | <tumour> A soft, extremely vascular sarcoma. (05 Mar 2000) |
| medullary sheath | <anatomy, neurology> An insulating layer surrounding vertebrate peripheral neurons, that dramatically increases the speed of conduction. It is formed by specialised Schwann cells, that can wrap around neurons up to 50 times. The exposed areas are called nodes of Ranvier: they contain very high densities of sodium channels and action potentials jump from one node to the next, without involving the intermediate axon, a process known as saltatory conduction. (18 Nov 1997) |
| medullary space | The central cavity and the cellular intervals between the trabeculae of bone, filled with marrow. (05 Mar 2000) |
| medullary spinal arteries | A large caliber spinal or radicular artery which courses centrally along a dorsal or ventral root, perhaps supplying it and the surrounding meninges in the fashion of any spinal/radicular artery, but which continues on to reach and anastomose with the anterior or posterior (longitudinal) spinal artery. Only 4-9 of the spinal arteries are medullary spinal arteries, found mainly in the lower cervical, lower thoracic and upper lumbar levels, the largest of which is the great radicular artery. (05 Mar 2000) |
| medullary sponge kidney | <radiology> Renal tubular ectasia, dilatation and cyst formation of collecting tubules in renal pyramids, Calcium most likely to be medullary nephrocalcinosis, not hereditary; males (2:1), usually bilateral associated with, renal tubular acidosis (RTA), Caroli disease, parathyroid adenoma, hypertrophic pyloric stenosis, Ehlers-Danlos syndrome, ipsilateral hemihypertrophy (12 Dec 1998) |
| medullary striae of fourth ventricle | Slender fascicles of fibres extending transversally below the ependymal floor of the ventricle from the median sulcus to enter the inferior cerebellar peduncle. They arise from the arcuate nuclei on the ventral surface of the medullary pyramid. Synonym: striae medullares ventriculi quarti, acoustic striae, auditory striae, Bergmann's cords, medullary teniae, teniae acusticae. (05 Mar 2000) |
| medullary stria of thalamus | A narrow, compact fibre bundle that extends along the line of attachment of the roof of the third ventricle to the thalamus on each side and terminates posteriorly in the habenular nucleus. It is composed of fibres originating in the septal area, the anterior perforated substance, the lateral preoptic nucleus, and the medial segment of the globus pallidus. Synonym: stria medullaris thalami, stria fornicis, stria ventriculi tertii. (05 Mar 2000) |
| medullary substance | The lipid material present in the myelin sheath of nerve fibres. Synonym: Schwann's white substance. (05 Mar 2000) |
| medullary teniae | Slender fascicles of fibres extending transversally below the ependymal floor of the ventricle from the median sulcus to enter the inferior cerebellar peduncle. They arise from the arcuate nuclei on the ventral surface of the medullary pyramid. Synonym: striae medullares ventriculi quarti, acoustic striae, auditory striae, Bergmann's cords, medullary teniae, teniae acusticae. (05 Mar 2000) |
| medullary tube | <embryology> The progenitor of the central nervous system. See: neural plate, neurulation. (18 Nov 1997) |