MH 086b Scalp

Hair Follicles

Only thin skin contains hair follicles and their associated sebaceous glands.

• Epidermis - stratified squamous keratinized epithelium
• Dermis - dense irregular connective tissue that supports the epidermis
  • Hair - shafts (which are absent in most follicles) are found at the center of hair follicles. The hair shaft contains a cortex and medulla surrounded by a thin cuticle (light pink).

• Root Sheaths -comprised of two parts:
  • Internal Root Sheath - extends from the hair bulb to the level of sebaceous glands. It is divided into Huxley's layer (inner layer of flattened cells) and Henle's layer (outer single layer of cuboidal cells).
  • External Root Sheath - layers of cells continuous with the epidermis
  • Glassy membrane - thick basement membrane that separates the hair follicle from the dermis

• Sebaceous Glands (#1,#2,#3,#4) - produce a lipid rich secretion called sebum that is released into the hair follicle. The clusters of cells have a clear cytoplasm because the lipid was extracted during tissue preparation.
• Eccrine Sweat Glands (#1,#2,#3) - coiled, tubular sweat-producing glands (lighter) and ducts (darker) with simple or stratified cuboidal epithelium
• Arrector Pili Muscles (arrows) - small muscles attached to hair follicles that cause hair to stand on end
• Hypodermis - loose connective tissue with adipose tissue