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Integumentary System
Anatomy & Physiology
Body Membranes
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Cover surfaces, line body cavities and form
protective sheets around organs
2 major groups
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Connective tissue membranes
Epithelial membranes
Connective Tissue Membranes
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AKA synovial membranes
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Made of connective tissue, no epithelial cells
Line fibrous capsules of synovial joints, bursae
and tendons
Secrete a lubricating fluid, providing a smooth
surface
Epithelial Membranes
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1. Mucous membranes
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Typically stratified squamos epithelium or simple
columnar epithelium
Epithelium resting on the lamina propria
(connective tissue sheet)
Many secrete a mucous
Lines all cavities open to the exterior; very moist
Functions in absorption and secretion
Epithelial Membranes
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2. Serous Membranes
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Layer of simple squamos epithelium laying on layer of
areolar tissue
Lines cavities closed to exterior
Occur in pairs
 Parietal layer lines the wall of the cavity
 Visceral layer lines the organ within that cavity
 Cavities separated by serous fluid
 Fluid allows for decreased friction between mobile organs
and cavity walls
Epithelial Membranes
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3. Cutaneous Membrane
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Aka the skin
Exposed to air and is a dry membrane
The Integumentary System
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The skin, hair, nails, sweat and oil glands
Mostly functions in protection but there are 6
separate functions of the skin
1.) Protection
2.) Body Temp. Regulation
3.) Cutaneous Sensation
4.) Metabolic Functions
5.) Blood Reservoir
6.) Excretion
Skin Functions
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1. Protection: 3 types of barriers
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A. Chemical barriers
 Includes skin secretions and melanin
 Acid mantle: kills bacteria on skin
B. Physical Barrier
 Provided by continuity of the skin and hardness of
keratinized cells
 Glycolipids: waterproof skin, blocking water & water soluble
substances
 Only lipid solubles can pass through
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CO2, O2, oleoresins, vitamins A,D,E & K
Skin Functions
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C. Biological Barrier
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Langerhan’s cells and macrophages
2.) Body Temp. Regulation
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Elevated: Blood vessels dilate & sweat glands
are stimulated
Lowered: Blood vessels constrict to conserve
body heat
Skin Functions
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3.) Cutaneous Sensation
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4.) Metabolic Functions
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Sunlight reacts with cholesterol in the body to form vitamin
D which helps to metabolize calcium
5.) Blood Reservoir
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Exteroreceptors respond to external stimuli
Holds large volumes of blood
6.) Excretion
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Wastes eliminated through sweat
Skin Regions
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Skin contains 2 major skin regions: dermis
and epidermis
1. Epidermis: thick, stratified squamos
epithelium
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Contains 4 different types of cells
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Keratinocytes
Melanocytes
Langerhans cells
Merkel cells
Epidermis Cell Types
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1.) Keratinocytes
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Makes keratin
Renews every 25-45
days
Found throughout
epidermis
Younger cells found in
deeper layers
Cells start to die as they
reach the surface
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2.) Melanocytes
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Makes the pigment
melanin
Accumulates on the
sunny side of the cell
Forms a pigment shield
against UV rays
Epidermis Cell Types
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3.) Langerhans
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From bone marrow
A type of macrophage
Activates immune
system
Can you break the word
macrophage down?
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4.) Merkel Cells
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Sensory receptors for
touch
Epidermal Skin Layers
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Thick skin: has 5 layers of skin
Thin skin: only has 4 layers of skin
Layers:
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Stratum Basale
Stratum Spinosum
Stratum Granulosum
Stratum Lucidum
Stratum Corneum
Stratum Basale
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The Basal Layer
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Deepest layer
Attached to dermis
Only 1 row of cells- the youngest keratinocytes
10-20% of melanocytes
Stratum Spinosum
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Prickly Layer
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Several layers thick
Has tension resistant filaments to toughen skin
Holds many langerhans, melanocytes and older
keratinocytes
Stratum Granulosum
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The Granular Layer
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3-5 cell layers thick
Contains flattened keratinocytes
Water proof glycolipids in extracellular space
Plasma membranes thicken
Stratum Lucidum
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The Clear Layer
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Present only in thick skin
Holds a few layers of clear, flattened, dead
keratinocytes
Stratum Corneum
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The Horny Layer
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Outermost layer
20-30 cell layers thick
Holds keratin and thickened plasma membranes
Glycolipids for water proofing
Remember….
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The epithelium is AVASCULAR so….
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Nutrients diffuse into epidermis from dermis
Layers above the granulosum too far away to
receive nutrients from diffusion
Dead cells shed from scalp and skin ~ 40-50
pounds in one lifetime
Dermis
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The second major skin region
Made of flexible connective tissue
Functions to bind body together
Holds sensory receptors, blood vessels,
lymphatic vessels, hair follicles, oil & sweat
glands
Has different cell types and 2 major layers
Dermal Cell Types
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Fibroblasts
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Macrophages
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For renewal
For protection
White Blood Cells
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For protection
Dermal Skin Layers
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Papillary Layer
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Thin and superficial
Holds many blood vessels
Holds dermal papillae: small projections with
nerve endings, capillary loops and touch
receptors
Papillae enhance gripping ability on palms and
soles
Dermal Skin Layers
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Reticular Layer
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80% of dermis
Made of dense, irregular connective tissue
Bundled collagen fibers-run in many directions
Collagen gives skin strength and prevents cuts
Elastin fibers provide stretch and recoil
Hypodermis
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The “other” skin layer
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Not a major skin region
Subcutaneous tissue deep to skin
Made of areolar and adipose tissues
Stores fat, anchors skin to muscles
Shock absorption & insulation
Skin Markings
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Dermal Tearings
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Extreme stretching of
skin
Appear as silvery, white
scars
AKA Striae: stretch
marks
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Blister
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Separation of epidermal
& dermal layers by a fluid
filled pocket
Flexure Lines
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Dermal modifications
Skin attached to deeper
structures to allow joint
movements
Skin Color
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1.) Melanin: only pigment made in skin
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Ranges from yellowish-red to brown to black
Amount and shade varies
The number of melanocytes relatively the same among
people
2.) Carotene
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Yellow to orange pigment
Found in plant products
Accumulates in stratum corneum and hypodermis
Skin Color
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Hemoglobin
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Pinkish hue of fair skin
Oxygen carrying protein
in skin
Red in oxygenated blood
Cyanosis
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Bluish tint due to low
oxygen levels
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Redness/Erythema
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Embarrassment, fever,
inflammation or allergy
Jaundice
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Yellow cast
Signifies liver problems
Skin Color
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Black and Blue Marks
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Contusions or bruises
Broken capillaries
causes blood to leak
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Pale skin
Emotional stress
Low blood pressure
Impaired blood flow
Skin Appendages
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3.
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Sweat glands
Sebaceous glands
Hair
Nails
Sweat Glands
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AKA Sudoriferous Glands
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Located everywhere except nipples & external
genitalia
Over 25 million glands/person
4 types
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Eccrine
Apocrine
Ceruminous
Mammary
Eccrine Glands
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Most abundant gland, especially palms, soles
& forehead
Pores connect ducts to skin surface
Releases sweat: 99% water, salt, vitamin C,
antibodies, wastes (urea), lactic acid
Unable to control
Assists thermoregulation
Eccrine Glands
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Heat induced sweat
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Starts on forehead and spreads inferiorly
Emotionally induced sweat
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Begins on palms, soles and armpits, then spreads
Apocrine Glands
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Larger glands and ducts
Empty into hair follicles
Same composition as eccrine sweat +
proteins and fatty substances
Viscous, milky/yellow color
Odorless, but bacteria decomposes it on skin
creating B.O.
Apocrine Glands
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Starts functioning @ puberty
Activated during pain and stress
Analogous to pheromones in animals
Sweat Glands Continued
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Ceruminous
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In the ear
Releases wax to deter
insects & block entry of
foreign materials
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Mammary glands
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Specialized sweat glands
Secretes milk
Sebaceous Glands
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Oil Glands
Located everywhere EXCEPT palms and
soles
Secretes SEBUM via hair follicles or skin
pores
Softens, lubricates hair and skin
Stimulated by hormones activated @ puberty
Glands involved in acne
Hair and Hair Follicles
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Function:
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Detects stinging insects
Guards head from physical trauma, heat loss &
sunlight
Eyelashes shield eyes
Filters particles & insects from air inhaled through
nose
Hair and Hair Follicles
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Structure
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Made of hard keratin
Stronger, more durable
Doesn’t flake like soft
keratin of skin
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Regions:
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Root: embedded in the
skin
Shaft: projects from skin
Shape of shaft
determines hair type
 Flat, ribbon-like
 Oval
 Round
Hair Layers
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Hair made of keratinized cells
1. Medulla: central core of hair; large cells
separated by air spaces
2. Cortex: bulky layer; surrounds medulla
with several layers of flattened cells
3. Cuticle: single layer of overlapping cells;
most heavily keratinized
Hair Structure
Hair Parts
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Hair Follicle
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Extends from epidermal
surface into the dermis
Root Hair Plexus
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Hair Bulb
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Expanded part of deep
end of follicle
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Knot of sensory nerve
endings wrapped around
hair bulb
Hair Matrix
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Actively dividing area of
new hair cells; older cells
have more keratin
Hair Parts
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Arrector Pili Muscle
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Small muscle cells
Contraction pulls hair follicle to upright position &
dimples skin surface
In response to fear and cold
Hair Extras
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Split Ends: an
abrasion causing
cuticle to wear away,
allowing cortex and
medulla to “frizz out”
Hair color: pigment
made by melanocytes
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Gray and white hairs due
to decreased melanin
production
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Vellus hair: body hair
of kids and adult
females; pale and fine
Terminal hair: coarser
and longer; darker;
grows in response to
hormones
Hair Extras
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Rate of growth:
varies, but on average
2mm/week
Growth cycles: has
active and resting
stages
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Hair life span:
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Scalp: active for ~4
years; inactive for ~2
months
Lose ~ 90 scalp
hairs/day
Eyebrows active for 3-5
months
Nails
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Structure:
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Scale-like modifications of the epidermis
Contains hard keratin
Functions:
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Used as tools
Same growth pattern as hair and skin
Skin Development
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Lanugo: downy hair “cloak” covering fetus
body, shed at birth
Vernix caseosa: white substance made by
sebaceaous glands to protect skin in womb
Baby’s skin: thin and transparent, thickens
and moistens with age
Skin Development
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Adolescence: oily, acne
Prime time for skin in 20’s-30’s
Visual changes occur due to abrasion,
chemicals, wind and sun, air pollutants and
bacteria
Old age: skin thins; decreases elasticity
Prevention: good diet, fluids, cleanliness,
sun avoidance