Download Overview of Skin - OCPS TeacherPress

Integumentary System
OUR 1ST SYSTEM!
Integumentary system
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Includes skin, sweat glands, sebaceous (oil) glands,
hair, and nails
SKIN (or cutaneous membrane or integument)
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Largest organ
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Makes up 16% of total body mass.
0.5 (eyelids) to 4 (heels) mm thick
Mostly 1-2 mm
About 2 square meters in adults
Weighs about 10-11 lbs
Fun Facts
Don’t write
THE LAYERS OF SKIN
Epidermis
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Superficial layer
Keratinized stratified squamous epithelium
Avascular
Cells are continually replaced
• Old cells “keratinize”- harden
THICK SKIN- 5 layers (palms, fingers,
soles of feet)
THIN SKIN- 4 layers (rest of body)
Epidermis cont.
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90% of cells are keratinocytes:
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produce keratin – a protein - protects skin
from heat, microbes, and chemical.
Produce lamellar granules
• release a lipid that decreases water entry and
loss
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8% melanocytes  melanin
Epidermis Layers (from deep to
superficial)
1. Stratum Basale (Base layer)- firmly attached to
the dermis, cells rapidly divide
2. Stratum Spinosum – cells start to flatten and
appear spiny, produce keratin
3. Stratum Granulosum- cells are flat and start to
die
4. Stratum Lucidum present only in thick skin;
clear, flat, dead cells
5. Stratum Corneum- durable overcoat of dead
cells, thickest layer
Dermis
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Deep to epidermis
Dense irregular connective tissue and elastic
fibers
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gives skin toughness and elasticity
Rich nerve and blood supply
Contains hair follicles, sebaceous glands (oil), and
sweat glands.
Pain and touch receptors
“stretch marks” (striae) caused by small tears in
the dermis
Subcutaneous layer – technically not a
layer of skin
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Hypodermis
areolar and adipose tissue
Insulation, protection, and contains
major blood vessels.
Check for understanding
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4 - I can explain to my peers characteristics
of each of the major layers of the skin
3 - I understand characteristics of each of
the major layers of the skin
2 - I understand, but need to review my
notes.
1 - skin has layers???
Skin accessory structures
Hair
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Function: protects the body
• Scalp: also decreases heat loss
• Eyebrows/eyelashes/nostrils/external ear:
protect eyes/nose/ears from foreign
particles.
• Also function in sensing light touch.
Hair anatomy
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Made of column of dead, keratinized
cells bonded together by extracellular
proteins
Shaft: above skin
Root: deep into dermis
Bulb:
• base; blood vessels nourish
Make-up of shaft and root
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Medulla: can be lacking
Cortex:
Cuticle: made of single layer of thin , flat
cells that are keratinized; arranged like
shingles
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Arrector pili: muscle
pulls the hair shafts
perpendicular to the
skin
Occurs when
emotionally upset or
cold
Hair growth
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Visible hair is dead, but portion of its root
are alive
Goes through a growth stage and resting
stage (scalp hair: 2-6 years, 3 months)
Normal hair loss: 70-100 hairs a day
Can by altered by chemotherapy,
radiation, age, genetics, gender,
emotional stress, rapid weight loss,
childbirth.
Nails
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Tightly packed,
hard, dead,
keratinized
epidermal cells
Consists of a nail
body, free edge and
a nail root
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Most active growing
region is the lunula,
half moon shaped
area at the base of
the nail.
Nail slides forward
over the nail bed.
Nail growth
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Determined by rate of mitosis of cells
deep to nail root.
Affected by age, health, nutrition
Function: help grasp small objects,
protection for ends of digits, and allow us
to scratch various parts of the body.
Sebaceous Glands (oil)
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Epithelial tissue
Gland lies in dermis and opens into hair follicle
Not on palm and soles, varied sizes elsewhere
Secrete sebum (fatty material, protein, and salt).
Coats hair prevents drying
Prevents too much evaporation from skin, keeps
skin soft and pliable, inhibits growth of certain
bacteria.
Oversecretion (due to hormones) causes acne due
to bacteria
Sudoriferous Glands (sweat)
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Epithelial tissue
Each gland is a tiny tube that starts as
a coil shaped ball
Two types:
• Eccrine – thermal regulation
• Apocrine – “cold sweat”: stimulated during
emotional stress and sexual excitement
1. Eccrine Glands
• Most numerous
• Active from birth
• Common on forehead, back, neck
• Originates in dermis
• Empties into pores on surface of skin
• Secrete: water, ions, urea, uric acid,
ammonia, amino acids, glucose, and lactic
acid.
• Function: regulate body temperature
through evaporation.
2. Apocrine Glands
• Found mainly in axillary and
inguinal regions.
• Originates in hypodermis
• Empties through a duct into hair follicle
• Same components of eccrine sweat plus
lipids and protein
• Stimulated during emotional stress and
sexual excitement
• Begin functioning at puberty
• Commonly called “cold sweat”
SKIN COLOR
What influences our
appearance?
Pigments:
1. melanin
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Produced from melanocytes of
epidermis
Varies by
• Color: yellow-brown-black
• amount
Freckles/moles
Natural “shield”
2. hemoglobin
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RBCs; carry O2
Hidden by melanin
3. carotene
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Yellow-orange pigment
From diet
Skin color as a diagnostic clue
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Cyanotic (bluish):
Jaundice (yellowish):
Erythema (red):
Pallor (paleness):
Functions of skin
1. Regulation of Body Temp.
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HOT
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COLD
• Blood rushes to skin – heat released
• Sweat- evaporation cools
• Blood moves to vital organs
• Goose bumps
2. protection
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1. keratin protects underlying tissues from
microbes, abrasion, heat, chemicals
2. Lipids: guards against dehydration
3. Sebum (oil): prevents skin and hairs from
drying and kills surface bacteria
4. Acidic pH of sweat inhibits growth of
bacteria
5. Melanin: shield against UV light.
3.
Cutaneous sensations
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Tactile: touch, pressure, vibration,
Thermal
Pain
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4. Excretion and absorption
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Excretion: sweat removes water and
small amounts of salts, carbon dioxide,
ammonia and urea
Absorption of some lipid-soluble
materials:
• Fat-soluble vitamins (ex. A, D, E,K)
• Lead, mercury
• Chemical in poison ivy
Medical application
of this function:
transdermal drug
administration (a
patch):
examples:
nicotine, hormones
to prevent
contraception
5. Synthesis of vitamin D
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UV activates a molecule to turn into
vitamin D (a hormone that aids in the
absorption of calcium from intestines into
the blood)
SKIN CANCER
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Cause: sun
Types:
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basal cell carcinoma
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Squamous cell carcinomas
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• 78% of all, from stratum basale, rarely metastasize
• 20% of all, squamous cells of epidermis, some tendency
to metastasize
Malignant melanomas
• 2% of all, from melanocytes, metastasize and kill rapidly
• Early detection: ABCD
RISK FACTORS
1.
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Skin type
Sun exposure
Family history
Age
Immunological status
Risk doubled in last 20 years: ozone
depletion and more time in sun/tanning
beds
Wound healing
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Repairs skin to normal (or near normal)
structure and function
2 types
1. Epidermal wound healing
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Center may penetrate dermis, edges
involve only slight damage to superficial
epidermal cells
Basal cells divide and migrate across
wound until they encounter basal cells
from the other side.
2. Deep wound healing
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Injury to dermis and subcutaneous layer.
Phases:
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Inflammatory phase: formation of blood clot
in wound; vasodilation enhances delivery of
helpful cells
Migratory phase: scab, epithelial cells migrate
beneath to bridge wound, scar tissue starts
(collagen fibers), blood vessel regrowth
• Proliferative phase: much growth of scar
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tissue, blood vessels, and epithelial cells
beneath scab
Maturation phase: scab sloughs off
(scar tissue: more collagen fibers densely
packed, less elasticity, fewer blood vessels,
may not have same # of hairs, glands or
sensory structures as undamaged skin)