Veterinary Gross Anatomy-II

Cerebral peduncles

CEREBRAL PEDUNCLES OR CRURA CEREBRI

• These are two broad bundles situated at the lower part of the midbrain and appear on the ventral face of the brain as two columns that emerge from under the pons and diverge forward to enter the cerebrum. At the point of disappearance, the optic tract winds obliquely across the peduncle.
• These contain the descending and ascending tracts of the spinal cord. Each peduncle consists of a dorsal part tegmentum, middle part the substantia nigra and the ventral part the crus cerebri.
• The crus cerebri consists of cortico-spinal, cortico-nuclear and cortico-pontine fibres. Substantia nigra is a layer of gray mater and composed of numerous deeply pigmented nerve cells and forming part of the extra-pyramidal system.
• At the dorsomedial aspect of each substantia nigra, an ovoid mass of nerve cells with pinkish tinge is seen.
• This is called as the red nucleus, which forms an important cell station in the extra pyramidal system and gives rise to the rubrospinal tract.
• The tegmentum is continuous with the pons and contains some fibre tracts.

• The inter penduncular fossa is a space formed between the cerebral peduncles optic tracts and chiasma.
• It accommodates a hollow tubercle known as tuber cinerium and small nodule like structure situated behind the tuber called mammillary body or corpus albicans.
•  Dorsally the tuber cinerium is connected with the third ventricle and ventrally with a conical tube the infundibulum.
• The infundibulum is attached to the pituitary gland.