Unit 4 – The Integumentary System. Integumentary System Also known as the Integument ◦ Accounts...
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Transcript of Unit 4 – The Integumentary System. Integumentary System Also known as the Integument ◦ Accounts...
Unit 4 – The Unit 4 – The Integumentary SystemIntegumentary System
Integumentary SystemIntegumentary SystemAlso known as the Integument
◦Accounts for 16% of your body weight
◦First line of defense◦Almost 2m2
Consists of 2 major components◦Cutaneous membrane◦Accessory structures
Integumentary SystemIntegumentary SystemCutaneous membrane has two
layers◦Epidermis◦Dermis
Accessory structures include:◦Hair◦Nails◦Exocrine glands
Integumentary SystemIntegumentary SystemBlood vessels and nerves are
found in the dermis
Deep to the dermis, is the subcutaneous layer (hypodermis)
Integumentary SystemIntegumentary SystemFunctions of skin and
subcutaneous layer:◦Protection◦Excretion◦Maintenance of body temperature◦Synthesis if vitamin D◦Storage of fats◦Detection of touch, pressure, pain,
temperature
THE EPIDERMISTHE EPIDERMISIntegumentary System
The EpidermisThe EpidermisStratified squamous epithelial tissue
◦Mostly keratinocytes (contains keratin)Is comprised of several layers (deep
to superficial) Stratum germinativum Stratum spinosum Stratum granulosum Stratum lucidum Stratum corneum
Thin Skin – covers most of your body
Thick skin – palms of hands, soles of feet
Epidermal LayersEpidermal LayersStratum germinativum
◦Deepest layer◦Attached to basal lamina◦Has epidermal ridges
Extend into dermis to strengthen bond between epidermis and dermis
Pattern of ridges are revealed in fingerprints◦Dominated by basal cells (germinative)
Stem cells that replace lost superficial cells◦Contains melanocytes – cells that make
melanin
Epidermal LayersEpidermal LayersStratum spinosum
◦8-10 layers of cells◦Made of freshly divided basal cells
Epidermal LayersEpidermal LayersStratum granulosum
◦“grainy layer”◦3-5 layers of cells pushed
superficially from stratum spinosum◦Make large amounts of keratin
Basis of hair and nails in humans Makes skin waterproof
◦Cells die in this layer
Epidermal LayersEpidermal LayersStratum lucidum
◦Found in the palms of your hands and soles of your feet
Epidermal LayersEpidermal LayersStratum corneum
◦The exposed surface of the skin◦15-30 layers of keratinized cells
It takes 15-30 days for cells to move from the stratum germinativum to the stratum corneum
Cells spend about 2 weeks in the stratum corneum before being shed
Epidermal LayersEpidermal LayersStratum corneum (con’t)
◦Is water resistant, but not waterproof Water evaporates at a rate of about
500ml/day Called insensible perspiration
Sweat glands produce sensible perspiration
◦Blisters are formed when the connections between superficial and deeper layers are damaged. Fluid collects between layers
THE DERMISTHE DERMISIntegumentary System
The DermisThe DermisLies between the epidermis and
the subcutaneous layerTwo major components
◦Superficial papillary layer◦Deeper reticular layer
The Papillary LayerThe Papillary LayerSuperficial portion of dermisAreolar tissueContains capillaries, lymphatics,
and sensory neurons that supply the surface of the skin
Contain dermal papillae that interlock with the epidermal ridges
Reticular LayerReticular LayerDeeper portion of dermisDense irregular connective tissue
◦Collagen and elastic fibersContains all cells of connective
tissue properAlso contains blood vessels,
lymph vessels and nerve fibers
Dermal Strength and Dermal Strength and ElasticityElasticityDermis contains both collagen and
elastic fiber◦Allows dermis to tolerate limited
stretching
Water also helps with flexibility and resilience◦Pinch test for dehydration
Aging, hormones, UV radiation damages elastic fibers◦Leads to wrinkles and sagging skin
Dermal Strength and Dermal Strength and ElasticityElasticityExtensive stretching of dermis can
exceed the elastic capabilities of the skin◦Complete recoiling of fibers is
prevented◦Result is stretch marks
Retin-A (derivitave of Vitamin A) can help repair the dermis and can lessen appearance of wrinkles and stretch marks.
Lines of CleavageLines of CleavageThe collagen and elastic fibers in
the dermis are usually arranged in parallel bundles◦Arranged to resist forces during
normal movement◦The pattern forms lines of cleavage
Lines of CleavageLines of CleavageWhy are the lines important?
◦Cuts parallel to the lines of cleavage will remain closed and heal with minimal scarring
◦Cuts perpendicular to the lines will be pulled open by the recoiling elastic fibers and will result in greater scarring.
THE SUBCUTANEOUS THE SUBCUTANEOUS LAYERLAYER
Integumentary System
The Subcutaneous LayerThe Subcutaneous LayerAlso known as the hypodermisConsists of areolar and adipose
tissue◦Very elastic
Superficial region contains blood vessels
Subcutaneous fat serves as an insulator and a major energy reserve for the body.
The Subcutaneous LayerThe Subcutaneous LayerAt puberty, distribution of fat
starts to differ between the sexes◦Men tend to store fat at the neck,
arms, low back, and buttocks◦Women tend to store fat at the
breasts, buttocks, hips and thighs◦Both can accumulate fat in the
abdominal region
ACCESSORY ACCESSORY STRUCTURESSTRUCTURES
Integumentary System
Hair and Hair FolliclesHair and Hair FolliclesHair – cover almost every surface
of your skin◦Exceptions are sides and soles of
feet, palms of hands, sides of toes and fingers, lips, portions of external genitalia
Body has 2.5 million hairs 75% NOT on your head
Hair is a nonliving structure produced by hair follicles◦Made of the protein keratin
Hair and Hair FolliclesHair and Hair FolliclesFunction of hair on head
◦Protect from UV radiation◦Cushion light blows to head◦Insulate skull
In nostrils and ear:◦Prevent entry of foreign particles
All hair serve as sensory receptors
Hair and Hair FolliclesHair and Hair FolliclesHave arrector pili muscles
attached to hair follicle◦When contracted, makes hair stand
up From emotions, cold (goose bumps) In furry mammals, this will increase
insulation, but doesn’t have that effect in humans
Hair and Hair FolliclesHair and Hair FolliclesHair will grow for 2-5 years
before being shed◦Grows about 0.33mm each day
While growing, the follicle will incorporate nutrients/chemicals into the hair shaft◦Can be useful for detecting disorders
or drugs.◦Can be used for DNA fingerprinting if
hair contains nucleated cells
Hair and Hair FolliclesHair and Hair FolliclesHair coloration is from the
melanocytes producing varying amounts of melanin in the hair follicle
Different forms of melanin will give hair a dark brown, yellow-brown, or red appearance
Glands In the SkinGlands In the SkinSebaceous (Oil) GlandsCan secrete oil from hair follicle
or directly onto skinThe secreted material is called
sebum◦Made of fatty acids, cholesterol,
proteins, and electrolytes◦Inhibits bacteria growth, lubricates
and protects hair, and conditions surrounding skin
Glands In the SkinGlands In the SkinSebaceous (Oil) Glands (Con’t)
◦Sebaceous follicles Glands NOT associated with hair follicles Discharge sebum directly onto epidermis Located on face, back, chest, nipples,
external genitalia Very active just before birth and during
puberty
Glands In the SkinGlands In the SkinSweat Glands
◦Also known as sudoriferous glands◦Two types
Apocrine sweat glands Found in armpits, around nipples, and pubic
region Secrete sweat into hair follicles Sticky, cloudy, odorous secretion Begin secreting at puberty This sweat is a nutrition source for bacteria,
which intensifies odor
Glands In the SkinGlands In the SkinSweat Glands (Con’t)
◦Two types Merocrine sweat glands
Discharge secretion directly onto surface of skin More numerous (2-5 million) than apocrine
glands Palms and soles have highest number
3000 per square inch Secretion is 99% water with some electrolytes
(mainly sodium chloride)
Glands In the SkinGlands In the Skin
NailsNailsProtect exposed dorsal surfaces of
the tips of the fingers and toesParts:
◦Nail body – visible portion of nail◦Nail bed – lies under nail body◦Lateral nail grooves – lateral borders of
nail body◦Lateral nail folds – portion of skin
overlapping lateral portion of nail body◦Free edge – distal portion extending past
nail bed
NailsNailsParts (con’t):
◦Hyponychium – thickened skin at distal end of nail bed
◦Nail root – forms the nail◦Eponychium (cuticle) – skin flap
covering proximal nail body◦Lunula – pale crescent at proximal end
of nail body
INJURY RESPONSEINJURY RESPONSEIntegumentary System
Injury ResponseInjury ResponseExcellent regeneration
capabilities and response to stresses.
Calluses form when repeated stresses from manual labor are placed on the skin◦The stem cells of stratum
germinativum divide more rapidly, thickening the skin in that area
Injury ResponseInjury ResponseThe process of injury repair can be
slow
Infection and fluid loss can complicate repair
The type of injury also determines rate of repair◦Thin, straight cut (incision) will generally
heal more quickly than a scrape (abrasion) because of the relative surfaces involved
Injury ResponseInjury ResponseBleeding occurs when the
damage extends into the dermis. Why?◦No vessels in epidermis
Injury ResponseInjury ResponseSteps to injury response
Step 1Bleeding occurs and mast cells
trigger the inflammatory response
Injury ResponseInjury Response
Step 2Blood clot (scab) forms
Restores integrity of epidermis Restricts microorganisms from entering area
Stratum germinativum cells migrate along edges of wound
Divide rapidly to replace epidermal cells
Macrophages patrol area collecting debris and pathogens
Injury ResponseInjury Response
Step 2 (con’t)Increased capillary formation
enhances blood flowCombination of blood clot,
fibroblasts, and new capillary network is called granulation tissue
Injury ResponseInjury Response
Step 3Over time, deeper portion of clot
dissolvesNumber of capillaries declineFibroblast activity leads to
increase in collagen fibers and ground substance
Epidermal cells have migrated over the network of collagen fibers
Injury ResponseInjury ResponseStep 4After several weeks, the scab is shedThe repairs do not restore the
integument to its original condition◦Dermis will contain abnormally large
numbers of collagen fibers, and few capillaries
Severely damaged hair follicles, glands, muscle and nerve cells are seldom repaired◦Replaced by fibrous tissue (Scar)
AGINGAGINGIntegumentary System
Aging and the IntegumentAging and the IntegumentEffects of aging on the integument
◦Thinning epidermis◦Decreased vitamin D production
Muscle and bone weakness
◦Decreased melanocyte activity More sensitive to sun
◦Decline in glandular activity Dry, scaly skin. Less perspiration means
increased overheating
◦Reduced blood supply to dermis
Aging and the IntegumentAging and the IntegumentEffects of aging on the integument
◦Hair follicles stop functioning Thinner, finer hair
◦Dermis thins Sagging and wrinkling occur
◦Decrease in sex hormones Hair characteristics and fat distribution change People of both sexes age 90-100 tend to look
alike◦Skin repairs more slowly
Repairs can take twice as long as a young adult
Recurring infections may result