ACCESSORY STRUCTURES OF THE SKIN
HAIR STRUCTURES
Hair are found everywhere on the body except the palms, the sides and soles of
the feet, the lips, and portions of the external genitalia.
The hair has two parts:
• Shaft: The part of the hair above the
surface of the skin
• Root: The part of the hair below the
surface
The structures associated to hair
Hair follicle
• Dermal and epidermal sheaths that
surround a hair root
Hair bulb
• Each hair bulb is tissue called hair papilla
concave at its end, and the concavity is occupied by vascular connective
Arrector pili muscle
• A smooth muscle, innervated by sympathetic nerve fibers
• Pulls hairs upright in the cold weather and when one is frightened
• The pull of the arrector pili muscle also causes dimpling of the skin surface, so-
called gooseflesh
HAIR STRUCTURES
Hair are found everywhere on the body except the palms, the sides and soles of
the feet, the lips, and portions of the external genitalia.
The hair has two parts:
• Shaft: The part of the hair above the
surface of the skin
• Root: The part of the hair below the
surface
The structures associated to hair
Hair follicle
• Dermal and epidermal sheaths that
surround a hair root
Hair bulb
• Each hair bulb is tissue called hair papilla
concave at its end, and the concavity is occupied by vascular connective
Arrector pili muscle
• A smooth muscle, innervated by sympathetic nerve fibers
• Pulls hairs upright in the cold weather and when one is frightened
• The pull of the arrector pili muscle also causes dimpling of the skin surface, so-
called gooseflesh
