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The cerebral crus (crus cerebri. crus means ‘leg’ in Latin.) is the anterior portion of the cerebral peduncle which contains the motor tracts, traveling from the cerebral cortex to the pons and spine. The plural of which is cerebral crura. In some older texts, this is called the cerebral peduncle, but presently, it is usually limited to ...
The region includes the tegmentum, crus cerebri and pretectum. By this definition, the cerebral peduncles are also known as the basis pedunculi, while the large ventral bundle of efferent fibers is referred to as the cerebral crus (crus means ‘leg’ in Latin.) or the pes pedunculi (pes means 'foot' in Latin.).
All the fibers from the corticopontine system terminate in the pontine nuclei.The fibers descend through the sublenticular and retrolenticular of internal capsule, then traverse the midbrain through the basis pedunculi (i.e. ventral part of cerebral peduncle) to reach the pontine nuclei and synapse with neurons that give rise to pontocerebellar fibers.
The cerebral peduncles each form a lobe ventrally of the tegmentum, on either side of the midline. Beyond the midbrain, between the lobes, is the interpeduncular fossa, which is a cistern filled with cerebrospinal fluid [citation needed]. The majority of each lobe constitutes the cerebral crus.
The retrolenticular part contains fibers from the optic system, coming from the lateral geniculate nucleus of the thalamus. More posteriorly, this becomes the optic radiation . Some fibers from the medial geniculate nucleus (which carry auditory information) also pass in the retrolenticular internal capsule, but most are in the sublenticular part.
The corticobulbar (or corticonuclear) tract is a two-neuron white matter motor pathway connecting the motor cortex in the cerebral cortex to the medullary pyramids, which are part of the brainstem's medulla oblongata (also called "bulbar") region, and are primarily involved in carrying the motor function of the non-oculomotor cranial nerves, like muscles of the face, head and neck.
Cerebral peduncle. Crus cerebri; Mesencephalic cranial nerve nuclei. Oculomotor nucleus (III) Edinger-Westphal nucleus; Trochlear nucleus (IV) Mesencephalic duct (cerebral aqueduct, aqueduct of Sylvius)
From this nucleus the fibers pass forward through the tegmentum, the red nucleus, and the medial part of the substantia nigra, forming a series of curves with a lateral convexity, and emerge from the oculomotor sulcus on the medial side of the cerebral peduncle.