Why does the size of the ventral horns of the spinal cord vary along its length?
a) the ventral horns contain both somatic motor and somatic sensory neurons.
b) the size of the ventral horns is influenced by the size of the cavity of the central canal of the spinal cord.
c) the ventral horns have the largest neurons in them.
d) the size of the ventral horns reflects the amount of skeletal musculature innervated at each level.

The size of the ventral horns reflects the amount of skeletal musculature innervated at each level.

Explanation:

The central nervous system consists of the brain and the spinal cord.

Both the brain and the spinal cord have white and gray matter present in them.

In the spinal cord, the arrangement is such that the gray matter is arranged on the outside whereas the white matter is arranged on the inside of the spinal cord.

The grey matter is itself arranged in sections which are known as horns and thus there are dorsal horns as well as ventral horns.

Amongst the ventral and dorsal horns the size of the ventral horns varies because of the variation in the amount of skeletal muscle that innervates at each level.