| pyramidal muscle | <anatomy, muscle> Origin, crest of pubis; insertion, lower portion of linea alba; action, makes linea alba tense; nerve supply, subcostal. Synonym: musculus pyramidalis, pyramidal muscle. (05 Mar 2000) |
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| pyramidal muscle of auricle | <anatomy> An occasional prolongation of the fibres of the tragicus to the spina helicis. Synonym: musculus pyramidalis auriculae, Jung's muscle, pyramidal muscle of auricle. (05 Mar 2000) |
| 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) |
| 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 fasciculus | 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) |
| 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) |
| apophysial fracture | Separation of apophysis from bone. (05 Mar 2000) |
| articular fracture | A fracture involving the joint surface of a bone. (05 Mar 2000) |
| atlas fracture | <radiology> Incidence: 4% of cervical spine injuries, site: posterior arch, anterior arch, massa lateralis, Jefferson fracture associated with: fractures of C7 (25%), fractures of C2 pedicle (15%), extraspinal fractures (58%) (12 Dec 1998) |
| avulsion fracture | A fracture that occurs when a joint capsule, ligament, or muscle insertion of origin is pulled from the bone as a result of a sprain dislocation or strong contracture of the muscle against resistance; as the soft tissue is pulled away from the bone, a fragment or fragments of the bone may come away with it. (05 Mar 2000) |
| axis fracture | <radiology> Incidence: 6% of cervical spine injuries, associated with atlas fractures in 8%, hyperflexion injury: odontoid fracture, type I avulsion of tip of odontoid (5-8%) difficult to detect, type II fracture through base of dens (54-67%) complication: nonunion, type III subdental injury (30-33%) prognosis: good, Differential diagnosis: os odontoideum, ossiculum terminale, hypoplasia/aplasia of dens, hyperextension injury: hangman's fracture (12 Dec 1998) |
| barton fracture | <radiology> Intra-articular fracture of distal radius, dorsal displacement of separated fragment, due to fall on outstretched hand see: wrist fractures (12 Dec 1998) |