MH 087b Scalp

Hair Follicles

Thin skin with longitudinal sections of hair follicles.

• Hair Follicle - longitudinal section.

• Hair Shaft - cells grow from the hair bulb, die and lose their cellular detail. The cortex is composed of keratinized cells with melanin, while the medulla contains vacuolated cells.
• Cuticle - squamous cells form the outermost layer of hair.
• Internal Root Sheath - only extends from the hair bulb to the level of sebaceous glands. The cellular detail also becomes less defined.
  • Huxley's Layer - single or double layer of flattened cells.
  • 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.

• Hair Bulb - contains a layer of basal epithelial cells that produce the cells that become the hair shaft and the inner root sheath. The epithelium is invaginated by a papilla of connective tissue that brings nutrients to the growing epithelium.
• Arrector Pili Muscles - small muscles attached to hair follicles that cause hair to stand on end.
• Sebaceous Glands - produce a lipid rich secretion called sebum that is released into the hair follicle. Large cells with a central nucleus and a foamy appearing cytoplasm.
• Eccrine Sweat Glands - coiled, tubular sweat-producing glands and ducts with simple or stratified cuboidal epithelium.