African pygmy hedgehog integumentary system — spines, mantle, and the orbicularis muscle
Overview of hedgehog skin — spines that are modified hairs set in a mobile skin mantle, and the circular orbicularis muscle that draws the mantle closed when the animal rolls up.
General educational reference only — not clinical or veterinary advice. Anatomy varies between individual animals; consult a licensed veterinarian for any health concern.
Spines are modified hairs
A hedgehog's spines are hairs: each is a single keratinized shaft grown from an ordinary follicle and thickened into a stiff, pointed structure. A spine is hollow and braced inside by longitudinal partitions, making it rigid for very little weight. Near the skin the shaft narrows into a flexible neck and ends in a bulb seated in the dermis, so a spine pressed from the tip bends and buckles at the neck rather than being driven back into the body.
The mantle and the orbicularis muscle
Spines cover the back and flanks in a mobile sheet of skin called the mantle, attached loosely to the body beneath. Around the rim of the mantle runs a large circular muscle, the orbicularis, which acts like a drawstring: as it contracts the edge of the spiny skin is pulled inward over the head, limbs and belly, while a broad muscular sheet beneath the skin draws the body up. The result is a sphere presenting spines on every surface.
Haired skin and spine replacement
The face, throat, belly and legs bear no spines; they carry coarse ordinary hair over thin skin. Spines are shed and regrown individually rather than in a synchronized molt, so the covering is renewed continuously. Newborn hedgehogs carry a first set of soft spines lying beneath swollen skin, which emerge within hours of birth and are later replaced by the adult set.
