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Chapter 6 Skin 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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Physiology of Skin Regulate body temperature Protection
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
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Physiology of Skin Excretion Synthesis of Vitamin D Immunity
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
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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 ( mm) melanocytes provide melanin rests on basement membrane stratified squamous
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Epidermal Cells Keratinocyte Melanocyte Produce keratin (protein)
Found at base of epidermis Produces melanin Responsible for skin color and absorption of UV radiation
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Epidermal Cells Langerhan’s cells Granstein cells
Interact with helper T-cells of the immune system Granstein cells Resistant to UV radiation Interact with other T-cells of immune system
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Epidermis Layers of Epidermis stratum corneum stratum lucidum
stratum granulosum stratum spinosum stratum basale
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Epidermal Layers 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)
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Epidermal Layers Stratum Spinosum Stratum Granulosum
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
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Epidermal Layers Stratum Lucidum Stratum Corneum
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
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Dermis on average 1.0-2.0mm thick contains dermal papillae
binds epidermis to underlying tissues irregular dense connective tissue muscle cells nerve cell processes specialized sensory receptors blood vessels hair follicles glands
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Dermal Layers 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)
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Dermal Layers 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
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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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Hair 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
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Anatomy of the Hair 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
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Anatomy of the Hair Root Hair follicle
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
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Anatomy of the Hair Papillae of the hair
Indentation of the bulb that is filled with loose connective tissue and many blood vessels
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Associates of the Hair Complex
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
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Sebaceous Glands holocrine glands secrete sebum
usually associated with hair follicles holocrine glands secrete sebum absent on palms and soles
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Clinical Application: Sebaceous Glands
Blackheads Sebaceous glands enlarge due to accumulated sebum Color of blackhead is due to melanin and oxidized oil, not dirt
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Associates of the Hair Complex
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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Associates of the Hair Complex
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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Sweat Glands sudoriferous glands widespread in skin
originates in deeper dermis or hypodermis
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Associates of the Hair Complex
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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Nails 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
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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 Physiological Factors
varying amounts of melanin varying size of melanin granules albinos lack melanin Physiological Factors dilation of dermal blood vessels constriction of dermal blood vessels accumulation of carotene jaundice Environmental Factors sunlight UV light from sunlamps X rays darkens melanin
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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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Skin Conditions Albinism Vitiligo Freckles Tanning
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
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Skin Color Carotene Capillaries 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
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Epidermal Wound Healing
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
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Epidermal Wound Healing
Superficial Wound Healing 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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Epidermal Wound Healing
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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Epidermal Wound Healing
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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Deep Wound Healing When the injury extends past the epidermis
Commonly due to accidental lacerations of surgical incisions Scar formation will occur Repair more complex (4 stages)
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Deep Wound Healing 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
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Deep Wound Healing 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
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Deep Wound Healing 3. Proliferative Phase
Epithelial cells grow under the scab Collagenous scar tissue is deposited Continued blood vessel growth
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Deep Wound Healing 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
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Healing of Burns 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
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Healing of Burns 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
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Healing of Burns Third degree burn autograft homograft 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
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Healing of Burns
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Rule of Nines 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
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Rule of Nines
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Life Span Changes Melanin production slows Skin becomes scaly
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 Skin becomes scaly Age spots appear Epidermis thins Dermis becomes reduced Loss of fat Wrinkling Sagging Sebaceous glands secrete less oil
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Clinical Application 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
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Clinical Application 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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Clinical Application Wrinkles Collagen fibers Elastic 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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Clinical Application 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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Clinical Application 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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Clinical Application 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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Clinical Application 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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Clinical Application Sunburn
Dead layers of cells peel off and leave unprotected layers of cells Ultra-violet rays of sunlight damage the cells’ DNA and RNA
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