It occupies the medial part of the base of the
posterior grey column and appears on the transverse section as a well-defined oval area. It begins caudally at the level of the second or third
lumbar nerve, and reaches its maximum size opposite the twelfth thoracic nerve. Above the level of the eight thoracic nerve its size diminishes, and the column ends opposite the last cervical or first thoracic nerve. It is represented, however, in the other regions by scattered cells, which become aggregated to form a cervical nucleus opposite the third cervical nerve, and a sacral nucleus in the middle and lower part of the sacral region. Nerve cells in the posterior thoracic nucleus are most abundant between the lower thoracic and upper lumbar segments. Cell bodies are of medium size and oval- or pyriform-shape. These cells characteristically present coarse Nissl granules and have characteristic eccentric nuclei. Axonal projections from neurons in this nucleus give rise to the dorsal
spinocerebellar tract which ascends ipsilaterally through the spinal cord and ends as
mossy fibers in the ipsilateral cerebellar cortex after passing through the inferior cerebellar peduncle. Axons originating from the posterior thoracic nucleus which ascend contralaterally through the
lateral funiculus of the
spinal cord are named
ventral spinocerebellar tract which cross over again within the white matter of the cerebellum, to ultimately end on its ipsilateral side. ==Function==