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Integumentary System
Functions
1. Covers and protects the body
What does the skin protect us from? Pathogens Injury Ultra-violet
radiation
Functions
2. Regulate body temperature
How does it regulate temperature?SweatingDilate/constrict
of blood vesselsGoose bumps
Functions
3. Excretes Waste
What
wastes are
excreted?
Urea
as sweat
subcutaneous
Functions
4. Reduces water loss
Keeps the body from drying out!
Functions
5. Houses sensory receptors
Mechano Chemo
Photo
Chemo
Mechano
Four basic types of integumentary tissue
Epithelium – epidermisConnective tissue - dermisMuscle tissueNervous tissue
There are 2 main layers of skin
I. Epidermis
II. Dermis
Epidermis
Keratinized stratified squamous epithelium Four types of cells
Keratinocytes – deepest, produce keratin (tough fibrous protein)
Melanocytes - make dark skin pigment melanin Merkel cells – associated with sensory nerve endings Langerhans cells – macrophage-like dendritic cells
Layers (from deep to superficial) Stratum basale or germinativum – single row of cells
attached to dermis; youngest cells Stratum spinosum – spinyness is artifactual;
tonofilaments (bundles of protein) resist tension Stratum granulosum – layers of flattened keratinocytes
producing keratin (hair and nails made of it also) Stratum lucidum (only on palms and soles) Stratum corneum – horny layer (cells dead, many layers
thick)(see figure on next slide)
Deadkeratinocytes
Lamellar granules
Keratinocyte
Langerhans cell
Melanocyte
Merkel cell
Tactile disc
Sensory neuron
Stratumcorneum
Stratumlucidum
Stratumgranulosum
Stratumspinosum
Stratumbasale
Dermis
Epidermis
Outer (surface) layers of skin10-30 cells thick
Two Parts:
Inner part composed of living cells
Outer part is of dead cells
Epidermis Inner layers
Lowest layer of cells reproduce and push older cells toward the surface.
As cells near the surface, they flatten and their organelle disintegrate
These cells also begin producing Keratin a tough, fibrous protein.
This replaces cytoplasm.
Epidermis Inner layers
Epidermis – Outer layers
The Keratin producing cells die as they move toward the surface.
Outer dead layer waterproofs and protects inner layers
It is shed continually and is completely replaced in 2 - 4 weeks
Epidermis
What do we find in the epidermis?Melanocytes
What are melanocytes?Cells that produce melanin.
What is melanin?A dark brown pigment
What does melanin do?Gives skin it’s colorProtects sensitive dermis from U-V radiation
Skin colorThree skin pigments
Melanin: the most importantCarotene: from carrots and yellow
vegiesHemoglobin: the pink of light skin
Melanin in granules passes from melanocytes (same number in all races) to keratinocytes in stratum basaleDigested by lysosomesVariations in colorProtection from UV light vs vitamin D?
Epidermis
Melanocytes
Do some people havemore melanocytesthan other people?
EpidermisSkin pigmentation is
due to the type and amount of melanin produced
Eumelanin produces darker pigments
Phaeomelanin produces lighter pigments and freckles
These often occur together in varying amounts
Dermis
Deeper layers of skin
10-20 times thicker
than epidermis.
Top layer arranged
In ridges.
Ridges help the
epidermis bind to the
dermis.
The uneven ridges
create fingerprints
Dermis
Accessory Organs of the Dermis1. Hair follicles – tube-like depression
where the hair develops
Hair and hair follicles: complexDerived from epidermis and dermisEverywhere but palms, soles, nipples, parts of genitalia
*“arrector pili” is smooth muscle
*
Hair papilla is connective tissue________________
Hair bulb: epithelial cells surrounding papilla
Functions of hairWarmth – less in man than other
mammalsSense light touch of the skinProtection - scalp
PartsRoot imbedded in skinShaft projecting above skin surface
Make up of hair – hard keratinThree concentric layers
Medulla (core)Cortex (surrounds medulla)Cuticle (single layers, overlapping)
Types of hair Vellus: fine, short hairs Intermediate hairs Terminal: longer, courser hair
Hair growth: averages 2 mm/week Active: growing Resting phase then shed
Hair loss Thinning – age related Male pattern baldness
Hair color Amount of melanin for black or brown; distinct
form of melanin for red White: decreased melanin and air bubbles in
the medulla Genetically determined though influenced by
hormones and environment
Accessory Organs of the Dermis2. Sebaceous glands – secret oily
sebum to soften and waterproof skin
Sebaceous (oil) glandsEntire body except palms and solesProduce sebum by holocrine secretionOils and lubricates
Accessory Organs of the Dermis3. Nails – protective covers of ends of
fingers and toes.
Nails
Of hard keratinCorresponds to hooves and clawsGrows from nail matrix
Accessory Organs of the Dermis4. Sweat glands:
secrete waste regulate heatproduces ear waxproduces milk during lactation
Sweat glands
Entire skin surface except nipples and part of external genitalia
Prevent overheating
500 cc to 12 l/day! (is mostly water)
Humans most efficient (only mammals have)
Produced in response to stress as well as heat
Types of sweat glands
Eccrine or merocrine Most numerous True sweat: 99% water, some salts, traces of
waste Open through pores
Apocrine Axillary, anal and genital areas only Ducts open into hair follices The organic molecules in it decompose with
time - odorModified apocrine glands
Ceruminous – secrete earwax Mammary – secrete milk
Types of sweat glands
Eccrine or merocrine Most numerous True sweat: 99% water, some salts, traces of
waste Open through pores
Apocrine Axillary, anal and genital areas only Ducts open into hair follices The organic molecules in it decompose with
time - odorModified apocrine glands
Ceruminous – secrete earwax Mammary – secrete milk
Accessory Organs of the Dermis5. Blood vessels – to nourish skin cells
Accessory Organs of the Dermis6. Nerves – to send and receive
messages
Subcutaneous
Accessory Organs of the Dermis7. Erector pilli muscle
-smooth muscle
-causes
“goosebumps”
-causes
hair to
stand erectsubcutaneous
Subcutaneous layer – connective tissueAnchors dermis to the body
Contains fat
cells to
protect
and cushion
Subcutaneous layer
Some disorders of the integumentary systemBurns
Threat to life Catastrophic loss of body fluids Dehydration and fatal circulatory shock Infection
Types First degree – epidermis: redness (e.g.
sunburn) Second degree – epidermis and upper dermis:
blister Third degree - full thickness
InfectionsSkin cancer
Disorders of the integumentary systemBurns
Threat to life Catastrophic loss of body fluids Dehydration and fatal circulatory shock Infection
Types First degree – epidermis: redness (e.g.
sunburn) Second degree – epidermis and upper dermis:
blister Third degree - full thickness
InfectionsSkin cancer
Interesting Tidbits
Your body is composed of approximately 100 Trillion cells
About 16% of your body weight is skinThe skin is completely renewed every 27
daysYou will make almost 1000 new skins in a
lifetime If all the layers of your skin were laid out
on the ground, it would cover about 20 m2 or 2 parking spaces
Interesting Tidbits
A fingernail or toenail takes about 6 months to grow from base to tip
Fingernails grow faster than toenails
An average human scalp has 100,000 hairs
We lose between 40 and 100 hairs per day
Blondes have more hair than brunettes
Interesting TidbitsFingerprints provide traction for grasping
objectsEven identical twins have different
fingerprintsEvery square inch of dermis contains
twenty feet of blood vesselsSkin on our hands and feet is thicker.
When we bathe, skin takes on water and swells slightly.
In the thicker areas, increased surface area creates crowding. The skin must wrinkle to accommodate the changes
Interesting TidbitsFriction of the epidermis causes cell
division to increase.This outward thickening is called a
callous.Sometimes growth is inward, creating a
corn.Humans shed about 600,000 particles of
skin per hour – about 1.5 pounds per year.
At age 70, you will have lost about 105 lbs of skin.