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
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