Chapter 5: The Integumentary System
•skin is the largest organ
•Functions of the skin:
1. Protection
- chemical
- physical
- biological
2. Body Temperature Regulation
vasodilate
vasoconstrict
3. Cutaneous sensations
4. Metabolic functions
5. Storage & Blood reservoir
6. Excretion
Insensible vs. sensible perspiration
Two layers of the skin:
Epidermis: surface layer
Dermis: deep layer
-hypodermis
A. Epidermis:
- stratified squamous
- avascular
- 4-5 layers deep
Cells of epidermis
1. Keratinocytes: produce
-keratin
-connected by desmosomes
-begin
2. Melanocytes: pigment melanin
- spider shaped
- found in
-melanin is formed in the cell & moved out towards processes
-melanin accumulates on the top of the nucleus
-all people have the same # of cells but differ in skin color due to difference in
melanocyte activity.
3. Langerhans cells
-formed in bone marrow &
-are star shaped macrophages
4. Merkel cells
-present in small numbers at the epidermis/dermis junction
-associated w/ a disc like ending of a sensory nerve
-merkel disc = merkel cell + dendrite
Layers of the epidermis: thicker skin has 5 layers (strata)
1. stratum germinativum (basal layer)
-deepest epidermal layer
-firmly attached to dermis
-consists mostly of
2. stratum spinosum (spiney layer)
-several layers thick
-melanin granules present here
-Langerhans cells
3. stratum granulosum (granular layer)
-thin zone
-keratin and keratohyalin
4. stratum lucidum (clear layer)
-consists of a few rows of flattened dead keratinocytes
-present only
5. stratum corneum (horny layer)
-outermost layer; protect against abrasion and penetration
- cell layers thick
-held tightly together by desmosomes
Carotene, Melanin and Dermal Circulation
Epidermis and Steroid Production

Vitamin D3 (cholecalciferol)
Epidermal Growth Factor (EGF)
B. Dermis
•cells found here are those typically found in connect. tissue
•gel-like matrix heavily embedded w/ collagen, elastin, & reticular fibers
•dermis is your "hide"
•richly supplied with
•Two layers
1. papillary layer: lots of blood vessels
-contain dermal papillae, Meissner's corpuscles
-epidermal ridges on ventral surface of hands & feet along with dermal papillae
arranged in patterns create
2. reticular layer
-80% of the thickness of dermis
-contains bundles of collagen fibers
-cleavage or tension lines in the skin
-stretch marks
-blister:
Subcutaneous Layer (hypodermis)
Hair:
•only hairless skin:
•primary function:
•3 layers: medulla, cortex, cuticle
1. medulla:
2. cortex:
3. cuticle: outermost
•hair grows as result of mitotic activity of epidermal cells at the bottom of the hair follicle
-hair growth is cyclic
-follicles extend from dermis --> epidermis
-portion of dermis protrudes into bottom of follicle forming a papilla which contains
•root:
•shaft:
•each follicle has a Sebaceous gland
 hair color determined by melanin
 arrector pili: smooth muscle
 Vellus hair vs. Terminal hair
Nails:
-thick, heavy keratinized cells
-Three regions
-lunula:
Sebaceous (Oil) glands

Sebum

Sebaceous follicles
Sweat (Sudoriferous) Glands:
- distributed all over the skin

Merocrine (Eccrine)

Apocrine

Ceruminous
Injury Response (figure 5-13)

Aging and the Integument pg 173
Skin cancers, Melanomas, Sunblocks pg 160
Burns and Grafts pg 172