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
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