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

TRACTS IN DORSAL WHITE COLUMN

• Fasciculus gracilis
• Comma tract
• Fasciculus cuneatus.
• The first two are ascending tracts conveying the same types of sensations.
• Fasciculus gracilis conveying impulses from the posterior parts of the body (posterior thoracic, lumbar, sacral and coccygeal) and the Fasciculus cuneatus conveying impulses from the anterior half (anterior cervical and thoracic).
• Both are in the dorsal white column, the F. gracilis being medial. The fibres in these tract are derived from the dorsal root of spinal nerves (without synapses in the dorsal gray column neurons) pass on the same side to the medulla oblongata, where they end in the gracile and cuneate nuclei.
• Fibres from these nuclei form the internal arcuate fibres curve towards the median line decussate and then continue as the medial lemniscus to terminate in the sensory nuclei in the thalamus. From here, the impulses are relayed to the sensory area in the cerebral cortex through the internal capsule.
• Both the tracts convey proprioceptive and discriminative touch or tactile sensations.