VAN 121: Veterinary Gross Anatomy-II (2+2)

HIND BRAIN

Dissection 

• The Pons, a transverse prominence on the ventral aspect of the brain stem between the cerebral peduncles and the medulla oblongata should be studied now.
• Cut the cerebellar peduncles, remove the cerebellum and make a transverse or horizontal section. Note the central gray substance in the centre of the white matter.
• Study the Arbor vitae - the tree like branching of the white matter in the sagittal section of brain.
• The medulla oblongata is now completely exposed.
• The dorsal surface form a greater part of the fourth ventricle and the restiform bodies diverge from the dorsal median position to form the lateral well of the posterior part of the fourth ventricle and then disappear into the cerebellum at its posterior peduncle.
• On the ventral surface of the medulla oblongata note the ventral median fissure of the spinal cord ending in a depression – the Foramen Caecum and behind the pons is another transverse prominence - the Corpus trapezoideum. On either side of the ventral median fissure are the pyramids.
• The fourth ventricle is bounded laterally by the brachium conjuctiva in front and by the restiform bodies behind.
• The dorsal face of the pons and medulla oblongata forms its floor. It communicates with the central canal of spinal cord at the Calamus scriptorius and with the third ventricle through the cerebral aqueduct.
• The cerebellum consists of a median lobe - the vermis and two lateral hemispheres and overlies the pons and the greater part of medulla oblogata, forming the roof of the fourth ventricle.
• The anterior medullary velum is thin lamina of white matter extending from the anterior extremity of the cerebellum to the midbrain.
• The cerebellum is connected to the other part of brain by the three pairs of peduncles, the anterior or brachium conjunctivum, the middle or the brachium pontis and the posterior or the restiform body.