1 Chapter 6 Skin and the Integumentary System Composed of several tissues Maintains homeostasis Protective covering Retards water loss Regulates body temperature

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Chapter 6Skin and the Integumentary

System• Composed of several tissues• Maintains homeostasis• Protective covering• Retards water loss• Regulates body temperature• Houses sensory receptors• Contains immune system cells• Synthesizes chemicals• Excretes small amounts of waste

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• Regulate body temperature– Sweat & change of blood flow toward surface of skin

• Protection– From abrasions, bacteria, dehydration, and ultra violet

radiation

• Reception of Stimuli– Nerve endings specifically designed for pressure,

temperature, touch and pain

Physiology of Skin

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• Excretion– sweat helps reduce levels of water, salts, and other

organic compounds

• Synthesis of Vitamin D– Helps manufacture vitamin D

– Helps body absorb calcium and phosphorus from food

• Immunity– Certain cells help in your ability to produce antibodies

Physiology of Skin

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Skin Cells

• Help produce Vitamin D needed for normal bone and tooth development

• Some cells (keratinocytes) produce substances that simulate development of some WBCs

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Layers of Skin

• Epidermis• Dermis• Subcutaneous layer

• beneath dermis • not part of skin

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Subcutaneous Layer

• hypodermis

• loose connective tissue

• adipose tissue

• insulates

• major blood vessels

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Epidermis

• lacks blood vessels• keratinized• thickest on palms and soles (0.8-1.4mm)• melanocytes provide melanin• rests on basement membrane• stratified squamous

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• Keratinocyte– Produce keratin (protein)

• Melanocyte– Found at base of epidermis– Produces melanin

• Responsible for skin color and absorption of UV radiation

Epidermal Cells

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• Langerhan’s cells– Interact with helper T-cells of the immune

system

• Granstein cells– Resistant to UV radiation– Interact with other T-cells of immune system

Epidermal Cells

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Epidermis

Layers of Epidermis• stratum corneum• stratum lucidum• stratum granulosum• stratum spinosum• stratum basale

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• Stratum Basale– Deepest layer– Single layer of cells capable of continued cell

division– Also called the stratum germinativum– Cells may migrate to the dermis to become glands

and hair follicles– Areas with no hair contain nerve endings that are

sensitive to touch (tactile disc)

Epidermal Layers

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• Stratum Spinosum– 8 to 10 rows of close fitting cells– Surface of the cells contain spine-like projections

that help to join cells together

• Stratum Granulosum– 3 to 5 rows flattened cells that contain dark stained

granules of keratohyalin, which is involved in the first steps of keratin formation

– Cells start to die in this layer

Epidermal Layers

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• Stratum Lucidum– Found only in thick skin of palms, and the

soles of your feet– 3 to 5 rows of clear, flat, dead cells

• Stratum Corneum– 25 to 30 rows of keratinized cells– Continuously replaced and shed

Epidermal Layers

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Dermis

• contains dermal papillae

• binds epidermis to underlying tissues• irregular dense connective tissue

• on average 1.0-2.0mm thick

• muscle cells

• nerve cell processes• specialized sensory receptors

• blood vessels• hair follicles

• glands

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• Papillary Layer– Upper 1/5 of the dermis

– Dermal papillae• Finger-like projections that increase surface area

• Projections that extend into the epidermis and may contain blood vessels or

• Meissner’s corpuscles- endings that are sensitive to touch

• Cause ridges in the overlying epidermis (fingerprints)

Dermal Layers

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• Reticular layer– Formed by closely packed irregularly arranged

connective tissue– Glands, hair, and nerves fill spaces between– Provides the skin with its strength and elasticity– Attached to underlying organs by the subcutaneous

layer– Pacinian Corpuscles

• Located in the subcutaneous layer• Nerve endings that are sensitive to pressure

Dermal Layers

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Hair Follicles

• epidermal cells

• tube-like depression

• extends into dermis

• hair root

• hair shaft

• hair papilla

• dead epidermal cells

• melanin• arrector pili muscle

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• Protects, guards scalp from the sun, eyes from foreign particles

• Hair in the ear and nose protect these structures from foreign particles and insects that might be inhaled or crawl into the ear

Hair

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• Shaft– Superficial portion that most of which projects above

the skin– Made up of 3 parts

• Medulla– inner portion that contains air spaces

• Cortex– Middle portion that makes the majority of the hair shaft– Contains pigment granules of dark hair & mostly air in light hair

• Cuticle– Outer most layers– Cells heavily keratinized– Arranged like upside-down shingles

Anatomy of the Hair

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• Root– Portion that penetrates the dermis and even the

subcutaneous layer– Contains the 3 portions like the shaft

• Hair follicle– Surrounds the root– Continuation of the stratum basale and stratum

spinosum layers of the epidermis– Base of each follicle enlarges and looks like an onion

shaped bulb

Anatomy of the Hair

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• Papillae of the hair– Indentation of the bulb that is filled with

loose connective tissue and many blood vessels

Anatomy of the Hair

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• Sebaceous (oil) glands– Found in association with hair follicles except on the

lips and eyelids– Secrete sebum

• Mixture of fats, cholesterol, proteins, and inorganic salts

– Function• Prevents hair from becoming brittle• Forms a film that prevents excess evaporation of water

from the skin• Keeps the skin soft and flexible• Inhibits the growth of certain bacteria

Associates of the Hair Complex

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• usually associated with hair follicles

• holocrine glands

• secrete sebum

• absent on palms and soles

Sebaceous Glands

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• Blackheads– Sebaceous glands enlarge due to

accumulated sebum

– Color of blackhead is due to melanin and oxidized oil, not dirt

Clinical Application: Sebaceous Glands

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• Sudoriferous Glands– Divided on basis of structure and location– 3 types

• Apocrine– Located in axilla and pubic region– Excretory duct open to hair follicles– Start to function at the onset of puberty– Emit an odor

• Eccrine– More common– Ducts open to the surface of the skin


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• Both Apocrine and Eccrine glands secrete:– Perspiration

• mixture of water, salts (NaCl), urea, uric acid, amino acids, ammonia, sugar, lactic acid and ascorbic acid

• Function:– Reduces body temperature by evaporation

– Elimination of waste


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• sudoriferous glands

• widespread in skin

• originates in deeper dermis or hypodermis

Sweat Glands

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• Mammary glands– Modified sudoriferous glands– Reproductive unit

• Ceruminous glands– Found in external auditory meatus – Produce ear wax that protect your ears from

foreign particles


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Nails

• protective coverings

• nail plate/nail body

• nail bed

• lunula

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• Average growth is about 1 mm per week• Protect the end of the digits and aid the

manipulation of small objects• 4 parts of the nail

– Free edge- extends past distal end of the digit– Body- majority of the visible nail

• Lunula- semilunar white part of the body

– Nail Root- hidden part of the nail that lies above the nail matrix

– Nail Matrix- functions to bring the growth of nails• when superficial cells become nail cells, push the whole

nail across the nail bed

Nails

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Regulation of Body Temperature

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Problems in Temperature Regulation

Hyperthermia – abnormally high body temperature

Hypothermia – abnormally low body temperature

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Skin Color

Genetic Factors• varying amounts of melanin• varying size of melanin granules• albinos lack melanin

Environmental Factors• sunlight• UV light from sunlamps• X rays• darkens melanin

Physiological Factors• dilation of dermal blood vessels• constriction of dermal blood vessels• accumulation of carotene• jaundice

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Skin Color

• Melanin– Pigment found primarily in the basale and

spinosum epidermal layers– Varies skin color from yellow to black– Number of melanocytes about the same for

all races– Skin color due to amount of pigment

melanocytes produce

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• Albinism– inability to produce melanin

• Vitiligo– loss of melanocytes from an area of skin

• Freckles– patches of melanin

• Tanning– Also associated with the melanin– Ultra-violet radiation increases melanocyte activity

Skin Conditions

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• Carotene– Found in the stratum corneum– People of Asian origin have carotene in fatty

areas of the dermis– Gives a yellowish hue to the skin

• Capillaries– cause the skin to have a pink appearance

Skin Color

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• Common skin wounds– Abrasions

• portions of the skin has been scraped away

– Laceration• irregular tear of the skin

– Puncture• hole “popped” through the skin

– Incisions• clean out through the skin

– Contusion (bruise)• Tissue below skin damaged• skin is not broken

Epidermal Wound Healing

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• Superficial Wound Healing1. Basale cells in the area of the wound break

contact with the basement membrane that connects the epidermis to the dermis

2. Basale cells enlarge and migrate across the wound


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3. Contact inhibition stops the migrating cells and turns cells in a new direction continues until cells are surrounded by similar cells

– Malignant (cancer) cells don’t follow the same rules

• continue to spread and invade other areas


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4. When the “floor” of the wound is covered• Cells divide to form new strata (layers)

• This thickens the epidermis and fills in the wound from the bottom upward

5. If a scab was formed, it will fall off when the new epidermis is thick enough to protect itself


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Healing of Cuts

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• When the injury extends past the epidermis

• Commonly due to accidental lacerations of surgical incisions

• Scar formation will occur

• Repair more complex (4 stages)

Deep Wound Healing

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1. Inflammatory phase– Inflammation-vascular

and cellular response to rid wound of dirt, infection, etc

– Blood clot forms to keep the edges of the wound close together

– Epidermal cells start to migrate

– Vasodilation floods the areas with phagocytic cells and fibroblast

Deep Wound Healing

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2. Migratory phase• Clot becomes scab and

epithelial cells continue migrating to bridge the wound

• Fibroblast synthesize scar tissue

• Damaged blood vessels begin to re-grow

Deep Wound Healing

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3. Proliferative Phase– Epithelial cells grow

under the scab

– Collagenous scar tissue is deposited

– Continued blood vessel growth

Deep Wound Healing

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4. Maturation Phase• Scab falls off• Collagenous fibers

become more organized• Blood vessels restored to

normal• Scar tissue• Dense blood vessels• May not contain hair,

glands, or sensory receptors

Deep Wound Healing

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• First degree burn – superficial partial-

thickness

– Dermal blood vessels dilate causing skin to warm and redden

– Mild edema (swelling)

– Surface layer sometimes shed

– Heals in a few days to 2 weeks

Healing of Burns

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• Second degree burn – deep partial-thickness

– Damages epidermis and some dermis

– Fluid escapes damaged capillaries causing blisters

– Healing depends on stem cells derived from epidermis but located deep within dermis

Healing of Burns



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• Third degree burn – full-thickness– Skin becomes dry, leathery– Red, black, white color– autograft

• Thin layer of skin taken from unburned area & transplanted– homograft

• Cadaver skin used to cover burn• Temporary for protection of underlying tissue and prevents infection

– various skin substitutes• Amniotic membrane• Artificial membranes composed of silicone, polyurethane, or nylon• Cultured epithelial cells

Healing of Burns

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Healing of Burns



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• Divides skin surface into regions, each accounting for 9% (or some multiple of 9%) of the total surface area

• Important for planning to replace body fluids and electrolytes

Rule of Nines

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Rule of Nines

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Life Span Changes

• Skin becomes scaly• Age spots appear• Epidermis thins• Dermis becomes reduced• Loss of fat• Wrinkling• Sagging• Sebaceous glands secrete less oil

• Melanin production slows• Hair thins• Number of hair follicles decrease• Nail growth becomes impaired• Sensory receptors decline• Body temperature unable to be controlled• Diminished ability to activate Vitamin D

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• Maglignant Melanoma– Cancer of the melanocytes

– Often caused from overexposure to ultra-violet light of the sun

– Most tumors involve basale cells, so they can be removed surgically

Clinical Application

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• Malignant Melanoma– Best treatment is prevention– Examine your skin for moles that develop

irregular appearance– Uneven surfaces or a mixture of colors or

change in size or start to bleed– Many of these may be a sign of developing

melanoma


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• Wrinkles– Collagen fibers

• stiffens, break apart and form a shapeless tangle

– Elastic Fibers• some elasticity, thicken

and fray

– Subcutaneous• decreases

– Sebaceous glands• atrophy leads to dry,

cracked skin




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• Melanocytes– Decrease of functioning melanocytes lead to gray

hair and atypical skin pigmentation

– Increase of size of some melanocytes can cause liver spots

– Older skin is more susceptible to pathological conditions like cancer and senile pruritis (itching)


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Acne Vulgaris

•most common skin disorder•sebum and epithelial cells clog glands•produces whiteheads and blackheads (comedones)•anaerobic bacteria trigger inflammation (pimple)•largely hormonally induced•androgens stimulate sebum production•treatments include antibiotics, topical creams, birth control pills

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• Cystic Acne– Scarring as a result of

severe acne

– Surrounding epidermal cells might be replaced by connective tissue

– Squeezing, pinching or scratching the lesion will increase the chance of developing cystic acne


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• Psoriasis– Symptoms are distinct,

reddish, small round skin elevations covered with scales

– Caused by abnormally high rate of epidermal cell mitosis

– Trauma, infection, stress, seasonal or hormonal changes can irritate

– Treatments include steroid ointments and natural sunlight (ultra-violet light)




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• Sunburn– Dead layers of cells

peel off and leave unprotected layers of cells

– Ultra-violet rays of sunlight damage the cells’ DNA and RNA




Documents

1 Chapter 6 Skin and the Integumentary System Composed of several tissues Maintains homeostasis Protective covering Retards water loss Regulates body temperature