Cutaneous Autonomic Innervation

Publisher Summary Peripheral adrenergic and cholinergic fibers are present and provide innervation to a number of organelles in the skin including hair follicles, blood vessels, sweat glands and arrector pili muscles. Unmyelinated nociceptive C fibers pierce the basement membrane to innervate the epidermis from a subdermal plexus that runs just below the basement membrane. Clinical skin biopsies can be stained with the pan-axonal marker protein gene product (PGP) 9.5 and imaged by light microscopy to highlight the nerve fibers that surround the sweat gland tubules. The complexity of sweat gland innervation limits the utility of descriptive and semiquantitative methods for determining sudomotor density. Hair follicles extend from the deeper dermal tissue, through the basement membrane and epithelial layer and extend beyond the border of the skin. Arrector pili muscles anchor hair follicles by attaching the shaft of the hair follicle to the dermal tissue. Upon stimulation, the contracting muscles cause piloerection with the formation of cutis anseri, or goose bumps. The decline in both sudomotor and pilomotor nerve fiber density parallels overall neuropathy progression and is associated with longer duration of diabetes and higher glycosylated hemoglobin levels.