| 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) |
| abdominal internal oblique muscle | <anatomy, muscle> Origin, iliac fascia deep to lateral part of inguinal ligament, anterior half of crest of ilium, and lumbar fascia; insertion, tenth to twelfth ribs and sheath of rectus; some of the fibres from inguinal ligament terminate in the conjoint tendon; action, diminishes capacity of abdomen, flexes lumbar vertebral column (bends thorax forward); nerve supply, lower thoracic. Synonym: musculus obliquus internus abdominis, abdominal internal oblique muscle. (05 Mar 2000) |
| anterior intercostal branches of internal thoracic artery | One of the arteries supplying the anterior portions of the intercostal spaces of the thoracic wall. Anterior intercostal arteries 1-6 arise as branches of the internal thoracic artery; 7-11 arise as branches of the musculophrenic artery. Synonym: rami intercostales anteriores, rami intercostalis anteriores arteria thoracica interna. (05 Mar 2000) |
| anterior limb of internal capsule | The portion of the internal capsule between the head of the caudate nucleus and the putamen; it lies anterior to the genu of the internal capsule. Synonym: crus anterius capsulae internae. (05 Mar 2000) |
| aponeurosis of internal abdominal oblique muscle | <anatomy> Broad, flat tendinous portion of the internal abdominal oblique muscle. The fleshy fibres of the muscle end in the aponeurosis lateral to the semilunar line. The uppermost portion of the aponeurosis is attached to the outer surfaces and lower borders of the seventh to ninth costal cartilages. Of the portion extending between the costoxiphoid margin and the pubis, the upper two-thirds splits into anterior and posterior laminae at the lateral border of the rectus abdominis muscle to contribute to the anterior and posterior walls of the sheath of the rectus abdominis muscle as they extend to the midline linea alba. The lower third of the aponeurosis does not split but joins the aponeuroses of the external abdominal oblique and transversus abdominis muscles to form the anterior wall of the sheath of the rectus abdominis muscle. The fibres of the portion of the aponeurosis contributing to the rectus sheath decussate with those of the contralateral aponeurosis in the linea alba. The lowermost portion of the aponeurosis blends with the aponeurosis of the transversus abdominis muscle to form the conjoint tendon, attaching to the pubic crest and often the pecten pubis, thus forming the posterior wall of the inguinal canal at the superficial inguinal ring. See: cremasteric fascia, conjoint tendon, rectus sheath. (05 Mar 2000) |
| basal tentorial branch of internal carotid artery | <anatomy, artery> A small branch from the cavernous part of the internal carotid artery to the base of the tentorium. Synonym: ramus basalis tentorii arteriae carotidis internae. (05 Mar 2000) |
| ganglionic branch of internal carotid artery | <anatomy, artery> Branch to trigeminal ganglion; a small branch of the cavernous part of the internal carotid artery to the trigeminal ganglion. Synonym: ramus ganglii trigeminalis. (05 Mar 2000) |
| marginal tentorial branch of internal carotid artery | <anatomy, artery> A small branch from the cavernous part of the internal carotid artery to the free margin of the tentorium. Synonym: ramus marginalis tentorii arteriae carotidis internae. (05 Mar 2000) |
| genu of internal capsule | The obtuse angle, opening laterally in the horizontal plane, formed by the union of the two limbs (crus anterius and crus posterius) of the internal capsule. Synonym: genu capsulae internae. (05 Mar 2000) |
| carotid artery, internal | Branch of the common carotid artery which supplies the anterior part of the brain, the eye and its appendages, the forehead and nose. (12 Dec 1998) |
| vessels of internal ear | Blood vessels of the internal ear, consisting of the labyrinthine artery and its branches and the labyrinthine veins and their tributaries. Synonym: vasa auris internae. (05 Mar 2000) |