peduncle (pe-dung´kl, pe´dung-kl)

1. In neuroanatomy, term loosely applied to a variety of stalklike connecting structures in the brain, composed either exclusively of white matter (e.g., cerebellar p.) or of white and gray matter (e.g., cerebral p. 2. pedicle (2) [Mod. L. pedunculus, dim. of pes, foot]
cerebral p. originally denoting either of the two halves of the midbrain (a relatively narrow "neck" connecting the forebrain to the hindbrain); this term has been variably used to designate only those large bundles of corticofugal fibers forming the crus cerebri, or to designate the crus cerebri plus the midbrain tegmentum; this latter more inclusive usage (crus cerebri and midbrain tegmentum) is preferred; the substantia nigra, while a part of the base of the p. (basis pedunculi), is considered a structure separating the midbrain tegmentum from the crus cerebri. See also crus cerebri.pedunculus cerebri [NA];
p. of corpus callosum subcallosal gyrus
p. of flocculus the bundle of afferent and efferent nerve fibers connecting the flocculus and the nodule of the cerebellum; part of its course is in the inferior medullary velum.pedunculus flocculi [NA];
inferior cerebellar p. large paired bundles of nerve fibers which develop on the dorsolateral surfaces of the upper medulla, extend under the lateral recesses of the rhomboid fossa and curve dorsally into the cerebellum medial to the middle cerebellar peduncle; composed of a larger (lateral) bundle, the restiform body, and a small (medial) bundle, the juxtarestiform body. Fibers forming this composite bundle originate from spinal neurons and medullary relay nuclei. The largest constituent (restiform body) is crossed fibers from the inferior olive; it also contains the dorsal spinocerebellar tract and cerebellar projections from the lateral reticular nucleus, the accessory cuneate nucleus, the paramedian reticular nuclei and the perihypoglossal nuclei. Vestibulocerebellar fibers are placed medially in the inferior cerebellar p. and are usually separately identified as the juxtarestiform body.pedunculus cerebellaris inferior [NA];
inferior thalamic p. a large fiber bundle emerging from the anterior part of the thalamus in the ventral direction, in part joining the medial fibers of the internal capsule, in other part curving laterally around the medial margin of the capsule into the innominate substance. Many of its fibers establish a reciprocal connection of the mediodorsal nucleus of the thalamus with the orbital gyri of the frontal lobe, but numerous other fibers constitute a conduction system from the amygdala and olfactory cortex to the mediodorsal nucleus. See also ansa peduncularis.pedunculus thalami inferior [NA];
lateral thalamic p. the massive group of fibers that emerges from the laterodorsal side of the thalamus to join the corona radiata; it reciprocally connects the lateral nucleus and the geniculate bodies of the thalamus with the corresponding regions of the cerebral cortex.pedunculus thalami lateralis;
p. of mamillary body a fascicle of nerve fibers passing to the mamillary body along the ventral surface of the midbrain; it consists of fibers that originate from the dorsal and ventral tegmental nuclei.pedunculus corporis mamillaris [NA], fasciculus pedunculomamillaris, pedunculomamillary fasciculus;
middle cerebellar p. the largest of three paired cerebellar p.'s, composed mainly of fibers that originate in the pontine nuclei, cross the midline in the ventral part of pons, and emerge on the opposite side as a massive bundle arching dorsally along the lateral side of the pontine tegmentum into the cerebellum; its fibers are distributed chiefly to the cortex of the cerebellar hemisphere.pedunculus cerebellaris medius [NA], brachium pontis;
olfactory p. olfactory tract
superior cerebellar p. a large bundle of nerve fibers that originate from the dentate and interpositus nuclei and emerges from the cerebellum in the rostral direction, along the lateral wall of the fourth ventricle. The bundle submerges from the dorsal surface of the brainstem into the mesencephalic tegmentum, where all of its fibers cross in the massive decussation of the superior cerebellar p.'s. Part of the bundle terminates in the contralateral red nucleus; the bulk of the fibers continue rostrally to parts of the ventral intermediate nucleus of thalamus, ventral posterolateral nucleus of thalamus, and central lateral nucleus of thalamus.pedunculus cerebellaris superior [NA], brachium conjunctivum cerebelli;
ventral thalamic p. the massive system of fiber bundles emerging through the ventral, lateral, and anterior borders of the thalamus to join the internal capsule and parts of the corona radiata; it contains the fibers reciprocally connecting the ventral thalamic nuclei with the precentral and postcentral gyri of the cerebral cortex.pedunculus thalami ventralis;


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