 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
yellow
up during jaundice, turns skin
 Below
epidermis
 Thicker
 Dense
tissue
connective
• 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
 Usually
growths
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