 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

 Nails stratified 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 Glands  Secrete sebum (oil) into hair follicle  Lubricates and waterproofs hair and skin  Bacteria in follicle produces red pimple

 Sweat Glands  Two 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

 1 st degree: only epidermis is affected  2 nd degree: all of epidermis and part of dermis affected  3 rd degree: all of the epidermis and dermis are destroyed  4 th degree: reaches muscle or bone  Can go up to 5 th 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