The Integumentary System

The Integumentary System

(Skin)

I. Introduction• The skin is like a coat for your body:

waterproof, stretchable, washable,

lasts a lifetime, and invisibly repairs

small cuts, rips, and burns

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II. Functions of SkinA. Protection

1. Mechanical damage - bumps, blows,

scrapes, cuts, etc.

2. Chemical damage - acidic or basic

substances

3. Thermal damage - heat or cold

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II. Functions of SkinA. Protection

4. UV radiation - produces melanin

5. Bacteria - barrier to germs

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II. Functions of SkinB. Body Temperature Regulation

1. Heat loss:

perspiration; dilation of

blood vessels near skin

2. Heat retention:

fat deposits; constriction of blood

vessels near skin

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II. Functions of Skin

C. Conservation of Body Water

*Keratin = waterproofing protein

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II. Functions of Skin

D. Excretion of Wastes

*Perspiration allows urea, uric acid,

sodium chloride, creatinine, lactic

acid, etc. to be released from the

body

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II. Functions of Skin

E. Receptors to Detect Outside Stimuli

*contains receptors that detect

temperature, pain, and pressure

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II. Functions of Skin

F. Vitamin Production

*contains sterols that convert to

Vitamin D when exposed to UV light

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III. Structure of the skin

III. Structure of the skin

A. Epidermis - outer skin layer composed

of stratified squamous epithelium

1. Sub-layers of the epidermis

III. Structure of the skin

a. Stratum corneum:

-top layer of the epidermis

-protective covering that contains

keratin

-barrier layer consisting of dead,

stratified squamous epithelium

III. Structure of the skin

b. Stratum lucidum:

-thin layer of clear cells

-contains eleidin (translucent

compound)

-found mainly in palms of hands and

soles of feet

III. Structure of the skin

c. Stratrum granulosum:

-consists of 3 - 5 layers of flattened

cells

-contains melanin

III. Structure of the skin

d. Stratum spinosum:

-consists of 8 - 10 layers of cells

-keratin is produced here

III. Structure of the skin

e. Stratum basale:

-deepest cell layer

-only cell layer in which cell division

occurs; receives nutrients from the

dermis

-most melanocytes found here

III. Structure of the skin

2. Why doesn’t a man bleed when he shaves, even though he is cutting off many cell layers?

- the epidermis is avascular

(no blood supply)

III. Structure of the skin

B. Dermis - dense connective tissue; “hide”, strong, stretchy layer that helps hold the body together

1. Sub-layers of the dermis

III. Structure of the skin

a. Papillary layer:

-outermost layer of dermis; attaches

epidermis to other skin layers

-has a blood supply

-contains fingerlike projections that

form ridges & bumps for traction

(fingerprints)

III. Structure of the skin

b. Reticular layer:

-deepest skin layer; makes up most of

the dermis and provides strength

“toughness”

-contains blood vessels, sweat & oil

glands, receptors, collagen & elastic

fibers

III. Structure of the skin

C. Hypodermis (subcutaneous tissue)

fatty layer that anchors skin to underlying organs; absorbs shock and insulates

IV. Skin Color

A. Three pigments contribute to skin color

1. Melanin - yellow to reddish brown

to black

2. Carotene

3. Hemoglobin

V. Appendages of the skin

A. Sebaceous (oil) glandsB. Sweat glands:

1. Eccrine - water; heat regulation 2. Apocrine - fats & proteins; puberty

C. HairD. Nails