Chapter 5Skin Histology

Epidermal Derivatives

J.F. Thompson, Ph.D.

Hair Distribution Varies Over the

Body Surface

Hair Follicles

Hair Anatomy• Shaft

– medulla - inner layer– cortex - middle layer, pigments, air spaces– cuticle - outermost layer, hard keratin

• Root– similar to shaft, but within dermis

• Follicle - surrounds root

• Sheath - supports shaft & root

• Bulb - enlarged layered structure at base where hair is generated– papilla - areolar connective tissue, blood

vessels supply nutrients– matrix - germination layer of papilla

(stratum basale) builds hair shaft

• Sebaceous glands – release oil

• Arrector Pili – smooth muscle

Hairs & Lice

egg

headlouse

crab louse

Arrector Pili (smooth muscle)

Sweat Glands

Sebaceous Glands

Nails• tightly packed, hard,

keratinized cells• nail matrix - under root

of nail– site of nail growth– transforms normal skin

cells into nail cells which push forward

– 1mm/week in fingers; slower in toes

– the longer the finger the greater the growth rate

Nails• Tightly packed cells with

hard keratin

• Nail matrix - under root of nail– site of nail growth– transforms normal skin

cells into nail cells which push forward

– 1mm/week in fingers; slower in toes

– the longer the finger the greater the growth rate

Hypodermis

End Ch 5

Skin HistologyEpidermal Derivatives