| FI | fasciculus intrafascicularis; fever caused by infection; fibrinogen; fixed interval; flame ionizatio... |
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| FLM | fasciculus longitudinalis medialis |
| FR | failure rate; film-screen radiograph; fasciculus retroflexus; febrile reaction; feedback regulation;... |
| MLF | medial longitudinal fasciculus; morphine-like factor |
| riMLF | rostral interstitial median longitudinal fasciculus |
| pyramidal process | The portion of the palatine bone passing lateral and posterior from the angle formed by the vertical and horizontal plates. Synonym: processus pyramidalis. (05 Mar 2000) |
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| pyramidal radiation | Corticospinal fibres passing from the cortex into the pyramid. Synonym: radiatio pyramidalis. (05 Mar 2000) |
| pyramidal tract | A massive bundle of fibres originating from pyramidal cells of various sizes in the fifth layer of the precentral motor (area 4), the premotor area (area 6), and to a lesser extent from the postcentral gyrus. Cells of origin in area 4 include the gigantopyramidal cells of Betz. Fibres from these cortical regions descend through the internal capsule, the middle third of the crus cerebri, and the ventral part of the pons to emerge on the ventral surface of the medulla oblongata as the pyramis. Continuing caudally, most of the fibres cross to the opposite side in the pyramidal decussation and descend in the dorsal half of the lateral funiculus of the spinal cord as the lateral pyramidal tract, which distributes its fibres throughout the length of the spinal cord to interneurons of the zona intermedia of the spinal gray matter. In the (extremity-related) spinal cord enlargements, fibres also pass directly to motoneuronal groups that innervate distal extremity muscles subserving particular hand-and-finger or foot-and-toe movements. The uncrossed fibres form a small bundle, the anterior pyramidal tract, which descends in the anterior funiculus of the spinal cord and terminates in synaptic contact with interneurons in the medial half of the anterior horn on both sides of the spinal cord. Interruption of the pyramidal tract at or below its cortical origin causes impairment of movement in the opposite body-half, especially severe in the arm and leg; characterised by muscular weakness, spasticity and hyperreflexia, and a loss of discrete finger and hand movements. Babinski's sign is associated with this condition of hemiplegia. Synonym: tractus corticospinalis, tractus pyramidalis, corticospinal tract. (05 Mar 2000) |
| pyramidal tractotomy | May be mesencephalic (pedunculotomy or crusotomy), medullary (medullary pyramidotomy), or spinal (spinal pyramidotomy). (05 Mar 2000) |
| direct pyramidal tract | Uncrossed fibres forming a small bundle in the pyramidal tract. See: pyramidal tract. Synonym: tractus corticospinalis anterior, tractus pyramidalis anterior, anterior corticospinal tract, anterior pyramidal fasciculus, direct pyramidal tract, fasciculus corticospinalis anterior, fasciculus pyramidalis anterior, Turck's bundle, Turck's column, Turck's tract. (05 Mar 2000) |
| lateral pyramidal tract | Those fibres of the pyramidal tract that cross to the opposite side in the pyramidal decussation and descend in the dorsal half of the lateral funiculus of the spinal cord; they are distributed throughout the length of the spinal cord to interneurons of the zona intermedia of the spinal gray matter. See: pyramidal tract. Synonym: tractus corticospinalis lateralis, tractus pyramidalis lateralis, crossed pyramidal tract, fasciculus corticospinalis lateralis, fasciculus pyramidalis lateralis, lateral corticospinal tract, lateral pyramidal fasciculus. (05 Mar 2000) |
| adrenal medulla | The inner part of the adrenal gland; it synthesises, stores and releases catecholamines. (12 Dec 1998) |
| renal medulla | The centre portion of the kidney. (27 Sep 1997) |
| medulla | The inner portion of an organ. (09 Oct 1997) |
| medulla glandulae suprarenalis | It is composed principally of anastomosing cords of cells in the core of the gland; the cells display a chromaffin reaction because of the presence of epinephrine and norepinephrine in their granules. Synonym: medulla glandulae suprarenalis, medulla of adrenal gland. (05 Mar 2000) |
| medulla nodi lymphatici | The central portion of a node consisting of cordlike masses of lymphocytes, plasma cells, and macrophages in a stroma of reticular fibres separated by lymph sinuses; it reaches the surface of the node at the hilum. Synonym: medulla nodi lymphatici. (05 Mar 2000) |
| medulla of adrenal gland | It is composed principally of anastomosing cords of cells in the core of the gland; the cells display a chromaffin reaction because of the presence of epinephrine and norepinephrine in their granules. Synonym: medulla glandulae suprarenalis, medulla of adrenal gland. (05 Mar 2000) |
| medulla of hair shaft | The central axis of some hairs, containing a column of large vacuolated and keratinised cells; the medullary portion is surrounded by the cortex. (05 Mar 2000) |
| medulla of kidney | The centre portion of the kidney. (27 Sep 1997) |
| medulla of lymph node | The central portion of a node consisting of cordlike masses of lymphocytes, plasma cells, and macrophages in a stroma of reticular fibres separated by lymph sinuses; it reaches the surface of the node at the hilum. Synonym: medulla nodi lymphatici. (05 Mar 2000) |