| medullary cords | Cord's of dense lymphoid tissue between the sinuses in the medulla of a lymph node. Synonym: lymph cords. (05 Mar 2000) |
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| medullary cystic disease | <disease> A rare hereditary kidney disease characterised by the gradual loss of kidney function due to the presence of cysts in the renal medulla. Symptoms include high urine output (cannot concentrate the urine), weakness, weight loss, nocturia, fatigue and headache. There is no cure and usually progresses from chronic renal failure to end stage renal disease. (27 Sep 1997) |
| medullary cystic kidney disease | <radiology> Mode of inheritance uncertain, usually affects young adults (early 20s), associated with red or blond hair (!!), causes salt wasting, polyuria, azotaemia, affects both kidneys, with progressive disease patients need dialysis or transplant (12 Dec 1998) |
| medullary folds | Synonym: neural folds. (05 Mar 2000) |
| medullary groove | The gutter-like groove formed in the midline of the embryo's dorsal surface by the progressive elevation of the lateral margins of the neural plate; the ultimate dorsal fusion of the margins results in the formation of the neural tube. Synonym: medullary groove. (05 Mar 2000) |
| medullary laminae of thalamus | Layers of myelinated fibres that appear on transverse sections of the thalamus; the lamina medullaris externa marks the ventral and lateral borders of the thalamus and delimits it from the subthalamus and reticular nucleus of thalamus; the lamina medullaris interna is interposed between the mediodorsal and ventral nuclei of the thalamus and encloses the intralaminar nuclei (centromedian, paracentral, and central lateral nuclei). Synonym: laminae medullares thalami, medullary layers of thalamus. (05 Mar 2000) |
| medullary layers of thalamus | Layers of myelinated fibres that appear on transverse sections of the thalamus; the lamina medullaris externa marks the ventral and lateral borders of the thalamus and delimits it from the subthalamus and reticular nucleus of thalamus; the lamina medullaris interna is interposed between the mediodorsal and ventral nuclei of the thalamus and encloses the intralaminar nuclei (centromedian, paracentral, and central lateral nuclei). Synonym: laminae medullares thalami, medullary layers of thalamus. (05 Mar 2000) |
| 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) |
| 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) |