Chapter 4Chapter 4Integumentary SystemIntegumentary System

Human Anatomy and Physiology

Integumentary SystemIntegumentary System

Composed of – skin – Sweat glands– Oil glands– Hairs– Nails

FunctionsFunctions

Protection against– Damage– Ultraviolet radiation– Desiccation (drying out)

Aids in temperature regulation Aids in excretion of urea and uric acid Synthesizes Vitamin D

Structure of SkinStructure of Skin Skin composed of two kinds of tissue that are firmly

connected to each other– Epidermis– Dermis

If these two layers separate, a blister forms. Deep to dermis is the subcutaneous tissue (hypodermis) –

not actually considered a layer of skin– Made of adipose tissue– Anchors the skin to underlying organs

Structure of SkinStructure of Skin

EpidermisEpidermis Made of stratified

squamous epithelium that can keratinize (become hard and tough)

Avascular – no blood supply of its own

Composed of five layers called strata– Stratum basale– Stratum spinosum– Stratum granulosum– Stratum lucidum– Stratum corneum

Layers of EpidermisLayers of Epidermis Stratum basale

– Deepest cell layer– Only epidermal cells that receive

adequate nourishment via diffusion of nutrients from the dermis

– Constantly undergoing cell division

Layers of EpidermisLayers of Epidermis

Cells move up to the next layer, Stratum Spinosum

Then, Stratum Granulosum where they start to become flatter, increasingly full of keratin and finally the cells die

Layers of EpidermisLayers of Epidermis

Stratum Lucidum– present where the skin

is hairless and extra thick, palms of hands and soles of feet

Layers of EpidermisLayers of Epidermis

Stratum Corneum– Outermost layer– 20-30 cell layers thick, ¾ of the epidermal thickness– Composed of dead cell remnants, completely filled

with keratin Keratin waterproofs skin

– Totally new epidermis every 25 to 45 days

MelaninMelanin Pigment that ranges in

color from yellow to brown to black

Produced by melanocytes found in the stratum basale

When skin exposed to sunlight, melanocytes produce more melanin and tanning occurs

MelaninMelanin

forms a protective umbrella over the cells’ nuclei which shields DNA from the damaging effects of the UV radiation

Freckles and moles are seen where melanin is concentrated in one spot

DermisDermis

Made of dense connective tissue

Two major regions:– Papillary layer– Reticular layer

Dermis – Papillary LayerDermis – Papillary Layer

– Upper layer– Contain dermal

papillae Uneven

fingerlike projections which indent the epidermis

Dermis – Papillary LayerDermis – Papillary Layer

Furnish nutrients to the epidermis

Provide fingerprints

Contain pain receptors: Meissner’s corpuscles

DermisDermis

Reticular layer– Deepest skin

layer

Dermis – Reticular LayerDermis – Reticular Layer

– Contains blood vessels, hair

follicles, sweat and oil glands

Rich nerve supplydeep pressure

receptors: Pacinian corpuscles

Dermis – Reticular LayerDermis – Reticular Layer

Contains:

–Collagen: responsible for toughness and attracts and binds water to help hydrate the skin

–Elastic fibers: give skin elasticity

• Decreases with age causing wrinkles

Dermis and Body Dermis and Body TemperatureTemperature

Blood vessels Sweat secretion

Skin ColorSkin Color Three pigments:

1. Melanin amount and kind – yellow, black, or brown

2. Carotene Orange-yellow pigment found in carrots and other

orange, deep yellow or leafy green vegetables

3. Amount of oxygen bound to hemoglobin Hemoglobin is the pigment in blood cells – gives

the crimson color – rosy glow

Appendages of the SkinAppendages of the Skin

Exocrine Glands– release secretions to

the skin surface via ducts

– Two groups: Oil glands

(sebaceous glands) Sweat glands

Hair and Hair Follicles Nails

Sebaceous GlandsSebaceous Glands

Oil glands Found all over skin

except palms and soles Produces sebum

– Lubricant that keeps skin soft and moist

– Contains chemicals that kill bacteria

Sebaceous Gland ProblemsSebaceous Gland Problems

Whitehead: blocked by sebumBlackhead: If sebum dries it darkensAcne: active infectionIncreased secretion during adolescence

cause skin problems

Sweat GlandsSweat Glands

More than 2.5 million per personTwo types:

– Eccrine glands– Apocrine glands

Eccrine Sweat GlandsEccrine Sweat Glands

More numerous Found all over body Produce sweat that

pours through pores Regulate body heat

SweatSweatSweat is a clear secretion that is made of

– water– salts– vitamin C– traces of metabolic wastes like ammonia, urea, uric acid,

and lactic acid (lactic acid attracts mosquitos)

Acidic (pH 4 to 6 )– Inhibits growth of bacteria

Apocrine sweat glandsApocrine sweat glands

Located mostly in axillary and genital areasDucts empty into hair folliclesBreakdown of secretion by skin bacteria

produces musky odor.

HairsHairs

Millions all over bodyServe protective functionHairs lost most of usefulness because we

have other means of keeping warm unlike the early humans.

Hair AnatomyHair Anatomy

Produced by hair follicle

Flexible epithelial surface

Root: part of hair enclosed in the follicle

Shaft: part of hair projecting from the surface

Why do my hairs stand on end?Why do my hairs stand on end?

Arrector pili – Muscles that connect

each side of the hair follicle to the dermal tissue

– When these muscles contract, the hair is pulled upright, causing “goose bumps”

NailsNails

Visible part is called nail body

Root is hidden by cuticle

Nail bed changes color with blood flow change

Tissue RepairTissue Repair

Tissue injury stimulates inflammatory response.

Wound healing (tissue repair) occurs two ways– Regeneration– Fibrosis

RegenerationRegeneration

Replacement of destroyed tissue by the same kind of cells

FibrosisFibrosis

Repair by dense connective tissue by the formation of scar tissue

Overview of Steps for Tissue Overview of Steps for Tissue RepairRepair

1. blood escapes from dermal blood vessels, and blood clot soon forms

2. blood clot and dried tissue fluid form a scab protecting the area blood vessels send out

3. branches and fibroblasts migrate into the area

4. fibroblasts produce new connective fibers, scab sloughs off

Steps of tissue healingSteps of tissue healing

Capillaries allow fluid rich in clotting proteins and other substances to seep into injured area from the bloodstream.

Leaked clotting proteins construct a clot, which stops loss of blood, holds wound together. This prevents bacteria from spreading to surrounding tissues.

Clot exposed to air, dries and hardens, forming scab

Steps of Tissue HealingSteps of Tissue Healing

Granulation tissue forms– Delicate pink tissue composed largely of

capillaries that grow into damaged area from undamaged blood vessels.

– Contain phagocytes that dispose of blood clot and fibroblast (connective tissue cells) that make collagen fibers (scar tissue) to permanently bridge the gap.

Steps of Tissue HealingSteps of Tissue Healing

Surface epithelium begins to regenerate and makes its way across the granulation tissue just beneath the scab, which then detaches.

Final result : fully regenerated surface epithelium that covers the scar.

Scar can be visible or invisible.

Keloid ScarsKeloid Scarsresult of an overly

aggressive healing process

extend beyond the original injury

may affect mobilityPossible treatments

include surgical removal, or injections with steroids

Contracture scarsContracture scars If your skin has been

burned, you may have a contracture scar, which causes tightening of skin that can impair your ability to move; additionally, this type of scar may go deeper to affect muscles and nerves.

Hypertrophic scarsHypertrophic scars

Raised and red scars that are similar to keloids, but do not breach the boundaries of the injury site.

Possible treatments can include injections of steroids to reduce inflammation.

Acne ScarsAcne Scars If you've had severe

acne, you probably have the scars to prove it.

FYI……FYI……

Epithelial Tissue regenerate easily.Connective tissue including bone regenerate

easily as well.Skeletal Muscle regenerates poorly, if at all.Cardiac Muscle and Nervous tissue are

replaced only by scar tissue.

Imbalances of the SkinImbalances of the Skin

Infections and Allergies– Athlete’s Foot– Boils and Carbuncles– Cold Sores– Contact dermatistis– Impetigo– Psoriasis

Burns– 1st degree– 2nd degree– 3rd degree

Skin Cancer– Basal cell carinoma– Squamous cell carcinoma– Malignant melanoma

ABCD RULE

Other Disorders– Erythema– Pallor– Jaundice– Decubitus ulcer– bruises

Infections and AllergiesInfections and Allergies Athlete’s Foot:

– itchy fungal infection of the toes

Infections and AllergiesInfections and Allergies

Boils and Carbuncles: – inflammation of hair

follicles and sebaceous glands

Infections and AllergiesInfections and Allergies

Cold Sores: – fever blisters; small

fluid filled blisters that itch an sting, caused by herpes simples infection

Infections and AllergiesInfections and Allergies

Contact dermatitis: – itching, redness, and

swelling of the skin, progressing to blistering

– Caused by exposure of the skin to chemicals like poison ivy that provoke allergic responses

Infections and AllergiesInfections and Allergies

Impetigo– Pink, water-filled raised

lesions that develop a yellow crust and eventually rupture

– Causes by a highly contagious staphylococcus infection

Infections and AllergiesInfections and Allergies Psoriasis

– Chronic condition characterized by reddened epidermal lesions covered with dry, silvery scales

BurnsBurns

Tissue damage and cell death caused by intense heat, electricity, UV radiation (sunburn), or certain chemicals (acids)

When the skin is burned, two life threatening problem result:

1. Dehydration

2. Infection

11stst threat: Dehydration threat: Dehydration

The body loses fluids containing proteins and electrolytes

This can lead to a shutdown of the kidneys and circulatory shock

22ndnd threat: Infection threat: Infection

Leading cause of deathBurned skin is sterile for about 24 hours,

but after that pathogens easily invade and multiply rapidly

Rule of NinesRule of Nines Divides the body area into 11 areas, each accounting

for 9 percent of the total body surface, plus 1% surrounding the genitals

BURNS

BurnsBurns

1st degree– Only the epidermis is

damaged– Becomes red and

swollen– Not usually serious and

generally heal in two to three days without any special attention

– sunburn

BurnsBurns 2nd degree

– Involve injury to the epidermis and the upper region of the dermis

– Skin is red and painful and blisters appear

– Re-growth of the epithelium can occur

– No permanent scars result if care is taken to prevent infection

BurnsBurns 3rd degree

– Destroy the entire thickness of the skin

– Appears gray-white or blackened

– Nerve endings are destroyed so the burn is not painful

– Regeneration is not possible

– Skin grafting must be done to cover the underlying exposed tissues

BurnsBurns

Considered critical if any of the following conditions exists:– 1. Over 25 % of the body has 2nd degree burns– 2. Over 10% of the body has 3rd degree burns– 3. Any third-degree burn of the face, hands, or

feet

Skin CancerSkin Cancer

Most skin tumors are benign and do not spread

Some are malignant (cancerous) and tend to invade other parts of the body

Skin cancer is the most common type of cancer in the body

Basal Cell CarcinomaBasal Cell Carcinoma Least malignant and most

common Full cure rate in 99% of

patients

Squamous Cell CarcinomaSquamous Cell Carcinoma

Believed to be sun-induced

If it is caught early and removed surgically, good chance of complete cure

Malignant MelanomaMalignant Melanoma Cancer of the melanocytes Accounts for 5% of skin cancers Often deadly – 50% survival rate Usually appears as a spreading

brown to black patch that metastasizes rapidly to surrounding lymph and blood vessels

ABCD RuleABCD Rule

Asymmetry: the two sides of the pigmented spot of mole do not match

Border Irregularity: The borders of the lesion are not smooth but exhibit indentations

Color: the pigmented spot contains areas of different colors

Diameter: the spot is larger than 6 mm in diameter (size of pencil eraser)

JaundiceJaundiceAn abnormal yellow

skin tone usually indicates a liver disorder in which excess bile pigments are absorbed into the blood, circulated throughout the body, and deposited in body tissues.

Decubitus ulcerDecubitus ulcer

Restriction of blood supply to the skin results in cell death, and if severe or prolonged, ulcers.

Occur in bedridden patients who are not turned regularly

BruisesBruises

Reveal sites where blood has escaped from the circulation and has clotted in the tissue spaces

Hematoma: clotted blood massAn unusual tendency to bruising may

signify a deficiency of vitamin C in the diet or hemophilia