1. Integumentary Appendages

2. Hair Chief parts of a hair
Filamentous strands of dead keratinized cells produced by hair follicles
Contains hard keratin which is tougher and more durable than soft keratin of the skin
Chief parts of a hair
Root – imbedded in the skin
Shaft – projects above skin's surface

3. Hair Hair Shaft organized into three concentric layers
Medulla – central core
Cortex – surrounds medulla
Cuticle – outermost layer
Pigmented by melanocytes at the base of the hair

4. Cross Section of a Hair
Figure 5.7a, b

5. Hair Follicle
Root sheath extending from the epidermal surface into the dermis
Deep end is expanded forming a hair bulb
Papilla - nipple-shaped indentation with blood vessels and nerves   
Matrix - germinal layer of cells (actively dividing cells) right above the papilla
A knot of sensory nerve endings (a root hair plexus) wraps around each hair bulb
Bending a hair stimulates these endings, hence our hairs act as sensitive touch receptors
Arrector pili muscle - bundle of smooth muscle contracts to make hair stand erect

6. Longitudinal Section of Follicle
Figure 5.7c, d

7. Hair Follicles

8. Hair Function and Distribution
Functions of hair include:
Helping to maintain warmth
Alerting the body to presence of insects on the skin
Guarding the scalp against physical trauma, heat loss, and sunlight
Hair is distributed over the entire skin surface except
Palms, soles, and lips
Nipples and portions of the external genitalia

9. Sebaceous Glands (oil glands)
Occur over entire body - Except palms and soles
Simple alveolar glands
Holocrine secretion – entire cell breaks up to form secretion
Secretes an oily substance called sebum
Most are associated with a hair follicle
Functions of sebum
Softens and lubricates hair and skin
Skin waterproofing
Collects dirt

10. Sweat (Sudoriferous) Glands
Two types:
Eccrine (Merocrine)
Most abundant sweat gland
“True sweat”
99% water with some salts
Contains traces of metabolic wastes ~ 2% urea
Role in thermoregulation
Widely present in skin (up to 500/cm2)
Apocrine
Odorous secretion
Absent before puberty
Present in axillary, areolar, anal and genital areas

11. Eccrine (Merocrine) Gland
Figure 5.10b

12. Nails Scalelike modification of epidermis made of hard keratin
Parts of the nail
Free edge
Body - dense mass of keratinized cells
Root
Nail folds
Eponychium – cuticle