Innervation of the Skin
The sympathetic fibers returning from the sympathetic trunk ganglia into the spinal nerves run in the peripheral nerves to the skin, where they innervate vessels, sweat glands, and erector pili muscles (vasomotor, sudomotor, pilomotor functions) in the corresponding derma-tomes. Segmental loss of these func-tions is of diagnostic significance in injuries to the spinal cord.
Clinical Note: In specific skin regions, Head’s zones (zones of hyperalgesia) (B), disease of anorgan may give rise to pain or hypersensitivity, with each organ being represented in a specific zone: diaphragm (B7) (C4), heart (B8) (T3/4), esophagus (B9) (T4/5), stomach (B10) (T8), liver and gallbladder (B11) (T8 – 11), small intestine (B12) (T10), large intestine (B13) (T11), urinary bladder (B14) (T11 – L1), kidneys and testes (B15) (T10 – L1). The Head’s zones are of practical im-portance in the diagnosis.