1 Anatomy of the Skin. 2 Most Important Function PROTECTION is the most important function of the integumentary system.

1

Anatomy of the Skin

2

Most Important Function

• PROTECTION is the most important function of the integumentary system

3

5 Major Functions

1. Serving as a barrier against infection and disease

2. Helping to regulate body temperature

3. Removing waste products from the body

4. Providing protection against Ultraviolet radiation from the sun

5. Producing vitamin D

4

Layers of Skin

• Epidermis• Dermis• Subcutaneous layer

• beneath dermis • not part of skin

5

Subcutaneous Layer

• hypodermis

• loose connective tissue

• adipose tissue

• insulates

• major blood vessels

6

Epidermis

• lacks blood vessels• keratinized• thickest on palms and soles (0.8-1.4mm)• melanocytes provide melanin• rests on basement membrane• stratified squamous

7

• Outermost layer of the skin• Its layers are made of Mostly DEAD CELLS. • Most of the cells of the epidermis undergo rapid

cell division (MITOSIS). • As new cells are produced, they push older cells to

the surface of the skin.  The older cells become flattened, lose their cellular contents and begin  making KERATIN.

Epidermis

8

• A TOUGH FIBROUS PROTEIN that FORMS THE BASIC STRUCTURE OF HAIR, NAILS, AND CALLUSES.

• Eventually, the Keratin-producing Cells (KERATINOCYTES) DIE AND FORM A TOUGH, FLEXIBLE WATERPROOF COVERING ON THE SURFACE OF THE SKIN.  Our thickest Epidermis is on palms of hands and soles of feet.

• OUTER LAYER OF DEAD CELLS IS SHED OR WASHED AWAY ONCE EVERY 14 TO 28 DAYS.

Keratin

9

Epidermis

Layers of Epidermis• stratum corneum• stratum lucidum• stratum granulosum• stratum spinosum• stratum basale

10

5 Layers of Epidermis• From superficial to

most deep• Stratum corneum• Stratum lucidum• Stratum granulosum• Stratum spinosum• Stratum basale

11

Dermis

• contains dermal papillae (fingerprints)

• binds epidermis to underlying tissues• irregular dense connective tissue

• on average 1.0-2.0mm thick

• muscle cells

• nerve cell processes• specialized sensory receptors

• blood vessels• hair follicles• glands

12

Hair Follicles

• epidermal cells

• tube-like depression

• extends into dermis

• hair root

• hair shaft

• hair papilla

• dead epidermal cells

• melanin• arrector pili muscle

13

Nails

• protective coverings

• nail plate

• nail bed

• lunula

14

Sebaceous Glands

• usually associated with hair follicles

• holocrine glands

• secrete sebum (oil)

• absent on palms and soles

15

Sweat Glands

• sudoriferous glands

• widespread in skin

• originates in deeper dermis or hypodermis

• eccrine glands

• apocrine glands

• ceruminous glands

• mammary glands

16

• Deep touch/pressure: Pacinian corpuscles

• Light touch/pressure: Meisner’s corpuscles

• Warm temperature: Free nerve endings

• Cold temperature: Free nerve endings

• Pain: Free nerve endings

Sensory structures of Dermis

17

Regulation of Body Temperature

18

Problems in Temperature Regulation

Hyperthermia – abnormally high body temperature

Hypothermia – abnormally low body temperature

19

Regulating body temperature

• The dermis helps us to control our body temperature:

• On a cold day when the body needs to conserve heat, the blood vessels in the dermis NARROW.

• On hot days, the blood vessels WIDEN, warming the skin and increasing heat loss.

• Tiny muscle fibers attach to hair follicles contract and pull hair upright when you are cold or afraid, producing what is commonly called Goose Bumps.

20

Skin Color

Genetic Factors• varying amounts of melanin• varying size of melanin granules• albinos lack melanin

Environmental Factors• sunlight• UV light from sunlamps• X rays• darkens melanin

Physiological Factors• dilation of dermal blood vessels• constriction of dermal blood vessels• accumulation of carotene• jaundice

21

Skin Color• The Epidermis contains MELANOCYTES, cells that

produce MELANIN, a dark brown pigment. • Both light skinned and dark skinned people have

roughly the same number of melanocytes, the difference in our skin color is caused by the amount of melanin the melanocytes produce and distribute.

• The amount of melanin produced in skin depends on TWO factors - Heredity and the Length of Time the Skin is Exposed to Ultraviolet Radiation (Tanning).

22

Skin Color

• Melanin is important for protection, by absorption of Ultraviolet Radiation from the sun.  All people, but especially people with light skin, need to minimize exposure to the sun and protect themselves from its Ultraviolet Radiation, which can damage DNA in skin cells and lead to deadly forms of skin cancer such as MELANOMA CANCER.

• THERE ARE NO BLOOD VESSELS IN THE EPIDERMIS, WHICH IS WHY A SMALL SCRATCH WILL NOT CAUSE BLEEDING.

23

Melanocyte

24

Melanocyte

25

Melanoma

26

Actinic Keratosis

Caused by sun damage. Can lead to squamous cell carcinoma.

27

EVOLUTION OF SKIN COLOR

• Balance between– Need for protection against UV radiation which

Causes skin cancer

Destroys folate (vitamin B)– Need for UV to produce vitamin D for calcium

absorption

28

Healing of Cuts

29

Healing of Burns

First degree burn – superficial partial-thickness

Second degree burn – deep partial-thickness-burns some dermis-fluid escapes from capillaries and builds up under epidermis causing blistering

Third degree burn – full-thickness• autograft (own skin transfer)• homograft (person to person [cadaver])• various skin substitutes

30

First Degree Burn

• Only the superficial epidermis is burned, and is painful but not blistered.

• Causes death of epidermal cells.

31

Second Degree Burn

• Deeper layers of epidermis are effected– And touches dermis

• Could have inflammation, blisters, and the burned skin is often painful.

32

Third Degree Burn• The entire epidermis is

charred or burned away, and the burn may extend into the dermis. 

• Often such a burn is not painful at first, if the receptors in the dermis have been destroyed.

33

Life Span Changes

• Skin becomes scaly• Age spots appear• Epidermis thins• Dermis becomes reduced• Loss of fat• Wrinkling• Sagging• Sebaceous glands secrete less oil

• Melanin production slows• Hair thins• Number of hair follicles decrease• Nail growth becomes impaired• Sensory receptors decline• Body temperature unable to be controlled• Diminished ability to activate Vitamin D

34

Clinical Application

Acne Vulgaris

•most common skin disorder•sebum and epithelial cells clog glands•produces whiteheads and blackheads •anaerobic bacteria trigger inflammation (pimple)•largely hormonally induced•androgens stimulate sebum production•treatments include antibiotics, topical creams, birth control pills

35

Common Skin Disorders

• If the Ducts of Oil Glands become clogged with excessive amounts of Sebum, Dead Cells, and Bacteria, the Skin disorder ACNE can result.

• When first wearing new shoes, the skin of the foot may be subject to friction.  This will separate layers of Epidermis, or separate the Epidermis from the Dermis, and tissue fluid may collect, causing a BLISTER.

• If the skin is subjected to pressure, the rate of mitosis will increase and create a thicker Epidermis; we call this a CALLUS.