What is the correct definition of a dermatome?

• A. Area of skin innervated by multiple dorsal nerve roots.
• B. Area of skin innervated by a single dorsal nerve root, individualized per person, regions can overlap.
• C. Area of skin with no sensory innervation.
• D. Area of skin innervated by ventral nerve roots.

Answer: (B)

Dermatomes are patches of skin that receive sensory input from a single spinal nerve root through the dorsal (sensory) root. Each spinal nerve carries afferent fibers for touch, pain, and temperature from its specific skin area to the spinal cord. Because this sensation comes from the dorsal root, a dermatome is tied to one nerve root rather than multiple ones, and ventral roots are responsible for motor signals, not sensory innervation. In addition, the exact borders between dermatomes can overlap, and the map can vary from person to person. So the correct definition is an area of skin innervated by a single dorsal nerve root, individualized per person, with possible overlap.