Two or more types of tissues grouped together, perform specialized functions

Largest organ?

Protective covering Regulates body temp Prevents water loss Sensory receptors Makes biomolecules Excretes waste Makes vitamin D

Epidermis, dermis, subcutaneous (hypodermis)

Outer layer Thin Made of stratified squamous

epithelial cells (no blood vessels) Constant cell division pushes older

cells upwards. Cells die off in 2-4 weeks

Keratin (protein) enters and hardens• Palms, soles of feet have lots!!

Skin color variations result from proteins in the epidermis

Melanin

Carotene

Hemoglobin

Bilirubin

Melanin: produced by melanocytes• Melanocytes about

equal in all people• Greater melanin

results in darker skin color

• Absence of melanin referred to as albinism

Carotene

• from beta-carotene

• Gives skin an orange-yellowish color

• Color lightens as carotene breaks down

Hemoglobin• Protein in blood• Capillaries in skin

dilate allowing more blood to flow to surface

• Gives skin a pinkish/reddish appearance

• Goes away when capillaries contract

Bilirubin

Builds up during jaundice, turns skin yellow

Below epidermis

Thicker

Dense connective tissue• Has projections

into epidermis to anchor it – causes spiraling patterns fingerprints

The dermis contains:

- nerve fibers - sensory fibers- hair follicles- sebaceous glands - sweat glands- blood vessels

Below dermis Binds skin to underlying organs Mostly adipose tissue

• Provides protection from shock• Insulation

Blood Vessels

*Not a true skin layer

-Interference with blood flow to the dermis can kill epidermal cells

-Lying in one position too long causes weight of body to block skin’s blood supply

-Treatment: shift patient, wound cleaning, massage

Hair• Grows from hair

follicle

• Arrector pili muscle makes hair “stand up” when cold

• Dead, keratinized, epidermal cells

Nailsstratified

squamous, keratinized, epithelial cells overlying the nail bed

the lunula is the most actively growing region of the nail root – (white section at proximal end of nail)

Sebaceous GlandsSecrete sebum (oil) into hair follicle

Lubricates and waterproofs hair and skin

Bacteria in follicle produces red pimple

Sweat GlandsTwo types -Eccrine: excrete sweat onto skin; respond primarily to body temp

-Apocrine: excrete sweat into hair; respond primarily to stress, also body temp and sexual arousal (become active during puberty)

Overactive sweat glands

-Hands-Feet-Armpits

Caused by overactive nervous system

Treatment:Antiperspirant

Iontophoresis Botox injections

Protection

Sensory reception- specialized cells embedded in skin detect hot, cold, pain, touch

Body temperature regulation –changes in blood vessel diameter and sweat gland production for hot/cold

Synthesis of Vitamin D• Molecules (dehydrocholesterol) exposed to

UV rays turn into vitamin D• Vitamin D converts into a hormone called

calcitronin in kidneys• Regulates calcium and phosphate levels• Prevents rickets• Promotes bone health

Non-pigmented epithelial cells

More common, slow growing

Light skinned people, over 40 years

Hard, dry, scaly growths

Usually surgically treated or with radiation

Malignant Melanoma• Serious- can lead to death

• Resembles a mole – dark spot

• Can be caused, by short, intermittent exposure to high intensity sunlight

• Any age

• First grows horizontal (surgically removed), then downward and can spread into deeper tissues

1st degree: only epidermis is affected

2nd degree: all of epidermis and part of dermis affected

3rd degree: all of the epidermis and dermis are destroyed

4th degree: reaches muscle or bone

Can go up to 5th degree

Body is divided into 11 sections• Each section takes about 9% of body’s

skin to cover it

Add up all areas of body that are burned badly enough to blister

Used in the field to determine where to take patient for treatment

•Subcutaneous: into subcutaneous layer; vaccines/flu shot insulin, morphine, penicillin

• Intradermal: into the dermis Local/regional anesthetics, allergy tests TB test

• Intramuscular: into the muscle Quick absorbtion; antibiotics, hormones, codeine, epinephrine, Botox

• Intravenous: into a vein Fluids, blood transfusions, lethal injections