Snake integumentary system — scales, ecdysis, and the spectacle
Overview of snake skin — scales as folds of one continuous epidermis, shedding of the whole outer layer in a single piece, and the transparent spectacle that replaces movable eyelids.
General educational reference only — not clinical or veterinary advice. Anatomy varies between individual animals; consult a licensed veterinarian for any health concern.
Scales and hinge skin
A snake's scales are not separate plates but thickened folds of one continuous epidermis, joined by thinner hinge skin that lets the body wall stretch around a large meal. The outer face of each scale is hardened with beta-keratin, the hinge with more pliable alpha-keratin. Dorsal scales may be smooth or keeled, and the ventral surface bears a single row of broad transverse scutes that engage the ground during locomotion.
Ecdysis as a whole-body event
Snakes renew the entire epidermis at once and shed it in a single continuous piece rather than in patches. A new epidermal generation forms beneath the old one, and fluid then separates the two along a cleavage zone, dulling the colors and clouding the eye for several days before it clears again. The snake loosens the old skin at the lips and snout and crawls forward out of it, turning it inside out.
The spectacle
Snakes have no movable eyelids. The embryonic lids fuse into a single transparent scale, the spectacle or brille, which covers the cornea and is part of the epidermis. Between it and the cornea lies a narrow subspectacular space filled with lacrimal fluid that drains through a duct into the roof of the mouth. Because the spectacle is skin, it is renewed and shed with the rest of the epidermis at every ecdysis.
