1. The first line of defense
Skin
The first line of defense

2. Functions Body temperature regulation Reservoir of blood
Protection from external environment
Cutaneous sensations
Excretion and absorption
Vitamin D synthesis

3. Epidermis Composed of: 1. Keratinocytes 2. Melanocytes
3. Langerhans’ cells
4. Merkel cells

4. Layers of epidermis Stratum basal (germinativum) 1. deepest layer
2. Cells are mitotic
3. contain melanocytes
4. usually one layer of simple columnar
epithelium

5. Stratum spinosum
1. Several layers thick
2. Cells are filling with keratin
3. Have melanin granules and
Langerhans’ cells

6. Stratum Granulosum
1. Cells flatten
2. nucleus and organelles
desentegrate
3. Lamellated granules coat cell
membranes
4. Cells die

7. Stratum Lucidum
1. Present only in thick skin
2. Cells become parallel

8. Stratum Corneum
1. Outermost cell layer
2. Cells are full of Keratin
3. Provides protection from
external environment
4. Flake off

9. Dermis Second major skin layer
Made of collegen and elastic connective tissue
Contains nerve fibers, blood vessels, and lymphatic vessels
Consists of two layers: Dermal papillae and reticular region

10. Dermal Papillae
Made of areolar connective tissue, collagen and elastin
Contain capillary loops
Form part of the dermal-epidermal junction
Contain corpuscles of touch (meissner)
Contain free nerve endings that sense: Pain, heat, tickling and itching
Form epidermal ridges that increase grip of hand and foot

11. Reticular Region Region deep to dermal papillae
Composed of dense irregular connective tissue with collagen and elastin interwoven
Contain a few cells between fibers: muscle fibers, sweat and oil glands, hair follicles, and Pacinian corpuscles

13. Skin Color Melanin 1. Polymer made of amino acid tyrosine
2. Range from yellow to reddish-brown to
black
3. Protects underlying tissues from UV light
Carotene
1. Yellow orange pigment
2. Most obvious where stratum Corneum is
Thickest
Hemaglobin
1. gives pinkish color to pale skin

14. Sudiferous glands Eccrine glands 1. Most numerous of sweat glands
2. secreting part found in dermis and
excretory part forms pore in skin
Apocrine glands
1. Found mainly in armpit and groin
2. secreting part found in subcutaneous
layer and excretory duct opens into hair
follicle
3. Do not function until puberty
4. Ceruminous (ear wax) and mammary glands

15. Sweat Hypotonic filtrate of blood
Contains water, salts, vitamin C, antibodies, urea, uric acid, amonia, and lactic acid
Regulated by sympathetic division of autonomic nervous system
Prevents overheating of the body

16. Sebaceous Glands
Connected to hair follicles with secreting portion in dermis
Secrete oily substance called sebum
Coats surface of hair to keep it from becoming dry and brittle
Keeps skin soft
Inhibits growth of some bacteria
Infections by bacteria that thrive on lipid rich sebum causes pimples

17. Hair

18. Hair structure Consists of dead keratinized cells
Shaft (superficial portion of hair)
Follicle (epidermal cells that grow down into dermis forming a tube)
Hair papilla (contains germinal layer of cells and blood vessels to nourish growing cells)
Root (developing hair that is contained in the follicle)
Follicle and dermal papillae attached by erector pili muscle

21. Hair growth
Germinal cells in the hair papilla reproduce, keratinize and die
Scalp hair grows for 2-6 years then rests for 3 months
When growth stage resumes old hair is shed

22. Nails Consist of hard keratinized cells that do not contain melanin
Nail body (visible part of nail)
Cuticle ( fold of skin that protects nail root)
Lanula (White part at base on nail)
Nail bed (epithelial cells that anchor nail body to finger tip
Root ( contain cells that reproduce mitotically to produce new cells