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Title: Skin

Skin its Appendages
  • Chapter 6

Integumentary System
  • Skin and its appendages (attachments)
  • Bodys thinnest, largest, most important organ
  • Appendages hair, nails, skin glands
  • Integument skin
  • Relatively flat organ classified as cutaneous

Structure of the Skin
  • Two main layers
  • Outer, thinner layer (or strata) epidermis
  • Composed of epithelial tissue
  • Inner, thicker layer of vascular connective
    tissue dermis
  • Dermal-epidermal junction where epidermis and
    dermis meet
  • Hypodermis lies beneath the dermis
    (subcutaneous tissue)
  • Rich in fat and areolar tissue
  • Fat content varies with state of nutrition

Structure of the Skin
  • Thin and thick skin refers to epidermis ONLY
  • Thin skin covers most of body surface
  • Thick skin palms of hands, soles of feet,
    finger tips
  • All 5 layers of epidermis present
  • Raised dermal papillae (fingerprints or
  • No hair is present in thick skin

Structure of Skin
Epidermis Cell Types
  • 3 cell types
  • Keratinocytes synthesize keratin
  • Keratin tough, fibrous protein found in hair,
    nails and outer skin
  • Keratinocytes make up 90 of epidermal cells
  • Principal structural element of outer skin
  • Melanocytes synthesize melanin (brown pigment
    gives skin color)
  • Melanin protects deeper layers from ultraviolet
  • Langerhan cells (immune cells)
  • Provide defense mechanism for the body
  • Arise from bone marrow migrate to the epidermis

Epidermis Cell Layers
  • 5 strata (cell layers)
  • Stratum corneum (horny layer)
  • Most superficial layer
  • Shingle-like dead cells
  • Cell shape squamous
  • Cytoplasm replaced by keratin
  • Keratinization process of cells formed from
    deeper layers, fill with keratin and push to the

Epidermis Cell Layers
  • 2. Stratum lucidum (clear layer)
  • Keratinocytes are anucleated and clear
  • Cytoplasm filled with Eleidin a protein-bound
    lipid that will eventually turn into keratin
  • Blocks water penetration and loss
  • Present only in thick skin

Epidermis Cell Layers
  • Stratum Granulosum (granular layer)
  • Keratinization begins in this layer
  • 2-4 layers of flattened cells
  • Cells in this strata are filled with granules
    called keratohyalin
  • Stratum spinosum (spiny layer)
  • 8-10 layers of irregular shaped cells with
    prominent intercellular bridges (connections)
  • Cells are rich with RNA for protein synthesis
    required for the production of keratin

Epidermis Cell Layers
  • Stratum basale (base layer)
  • Single layer of columnar cells
  • Mitosis only occurs here
  • Cells originate from here ? migrate to
    superficial layers ? shed
  • Stratum germinativum (growth layer)
  • Used to describe the stratum spinosum and the
    stratum basale together

Structure of Skin - Epidermis
Epidermal Growth Repair
  • Regeneration time time period required for
    population of cells to mature reproduce
  • Time for new cell formation rate of old
    keratinized cells flaking off
  • Helps maintain constant thickness of epidermis
  • Cells push upward into each layer ? die ? become
    keratinized ? desquamate (fall away/shed)
  • Regeneration time is approximately 35 days

Dermal-Epidermal Junction
  • Composed of basement membrane
  • Also contains specialized fibrous elements
    polysaccharide gel that cements epidermis to
  • Partial barrier to passage of some cells and
    large molecules

Dermis or corneum (true skin)
  • Thicker than epidermis
  • Protective function against mechanical injury
  • Storage area for water and electrolytes
  • Contains somatic sensory receptors (nerves
    nerve endings)
  • Process information such as pain, pressure,
    touch, temperature
  • Muscle fibers, hair follicles, sweat sebaceous
    glands, blood vessels
  • Rich vascular supply of the dermis plays a
    critical role in regulation of body temperature

Papillary Layer of Dermis
  • Thin layer
  • Loose connective tissue with elastic and
    collagenous fibers
  • Dermal papillae bumps that project into
  • Creates distinct ridges on epidermal surface of
    fingers toes (finger/footprints) unique for
    every person
  • Creates a gripping surface

Reticular Layer of Dermis
  • Thick layer
  • Dense irregular connective tissue
  • Network of fibers collagenous elastic
  • Contains muscle skeletal smooth (allows for
    point of attachment for movement)
  • Skeletal muscle scalp movement facial
  • Arrector pili muscles small bundles of smooth
    muscle that causes hair to stand on end which
    causes the skin around it to raise goosebumps
  • Somatic sensory receptors for pain, pressure,
    touch and temperature
  • Ex tactile (Meissner) corpuscle senses light
    touch pressure

Structure of Skin
Skin Receptors
Dermal Growth Repair
  • Does not shed regenerate like the epidermis
  • Rapid regeneration only occurs during wound
  • Dense fibrous connective tissue fills
    wound/incision/injury site to form a scar
  • Langers Cleavage lines collagenous fibers in
    dermal layer tend to orient themselves in
    patterns that differ from one body part to

Langers Cleavage Lines
Dermal Growth Repair
  • Stretch marks due to dermal tearing ? heal ?
    results in tiny scars
  • Ex pregnancy, rapid weight gain/growth

Questions Answer in complete sentences
  1. Identify the two main or primary layers of skin.
    What tissue type dominates each layer?
  2. The terms thin and thick refer to which primary
    layer of skin? How do thick and thin skin differ?
  3. Identify the three cell types found in the
    epidermis. Give a description of all three.
  4. List the five layers (or strata) of the
    epidermis. Give a brief description of each
    layer. Is each layer found in both thin and
    thick skin?
  5. What is the name of the glue-like layer
    separating the dermis from the epidermis?
  6. What structure forms the bumps that produce
    ridges on the palms and soles? Which layer of the
    dermis is this structure located in?
  7. Which layer is vascular the epidermis or dermis?
    What important role does the dermal vasculature

What Determines Our Skin Color?
  • Skin Pigments 2 types
  • Melanin brown pigment
  • Skin color determined by quantity of melanin
  • Melanocytes convert the amino acid tyrosine to
    melanin process catalyzed with tyrosinase
  • Majority of melanocytes found in stratum basale
  • Amount of melanin produced depends on genetics,
    sun exposure, age and hormones ACTH)
  • Ex Albinism (albino individuals) tryrosinase
    is absent from birth melanin cannot be

Skin Color
  • Carotene yellow pigment
  • Pigment found in food
  • Can deposit in stratum corneum of thick skin
    (palms soles of feet)
  • Other determinants of skin color
  • Changes in the vasculature
  • Blood vessels constrict pale
  • Blood vessels dilate blush
  • Poorly oxygenated hemoglobin (low oxygen
    saturation) causes cyanosis (bluish color to

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Functions of the Skin
  1. Protection
  2. Sensation
  3. Movement without injury
  4. Excretion
  5. Endocrine functions (vitamin D)
  6. Immunity
  7. Temperature regulation

  • Surface film thin film of emulsified materials
    spread over the skins surface
  • Produced from the mixture of residue/secretions
    from sweat sebaceous glands with epithelial
    cells constantly being shed
  • Function of the surface film
  • Antibacterial antifungal activity, lubrication,
    hydration of the skin surface, buffering of
    caustic irritants, blockage of toxic agents
  • Keratin protects against dehydration,
    microorganisms, chemical/mechanical damage
  • Melanin protects against ultraviolet radiation

  • Sensory receptors serve as antennas that detect
  • Pressure, pain, temperature, touch
  • Ex tactile corpuscle

Movement Growth
  • Movement and growth of the body as a whole can
    occur due to the presence of elastic fibers in
    the skin

  • Body regulates volume and chemical composition of
    sweat through functions of the skin
  • Skin influences fluid volumes in the body waste
    products excreted from the skin
  • Ex uric acid, ammonia, urea

Vitamin D Production
  • Endocrine process
  • First steps of vitamin D production occurs in the
    skin when exposed to ultraviolet light
  • Vitamin D synthesis is completed in the kidneys

  • Specialized cells are present in the skin
  • Ex langerhan cells with help from helper T cells
    trigger immune reactions

Regulation of Body Temperature
  • Majority of heat production is the result of food
    metabolism and activity of muscles and glands
    (esp the liver)
  • Vasocontriction prevents heat loss ? warm blood
    circulating deeper within the body
  • Vasodilation increases heat loss ? increases
    skins blood supply ? heat lost to the external
  • Evaporation, radiation, conduction and convection
  • Homeostasis of body temperature controlled by
    negative feedback mechanism

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  • Tissue injury or skin cell death that results
    from heat/fire, overexposure to ultraviolet
    light, contact with electrical current, corrosive

Burns Estimating Affected Body Surface
  • Treatment prognosis of a burn depends largely
    on the amount of skin surface affected
  • Rule of palms the size of the patients palm
    is approximately 1 of their body surface
  • Rule of nines
  • Body surface divided into 11 areas (anterior and
    posterior) of 9
  • Perineum (genital area) accounts for 1

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Severity of Burns
  • First degree burns usually caused by a sunburn
  • only epidermis is damaged
  • skin is red and swollen, no blistering
  • Second degree burns
  • Epidermis and dermis are damaged
  • damage to sweat glands, hair follicles, and
    sebaceous glands
  • Blisters, severe pain, swelling and scarring are
  • Third degree burns (full thickness burns)
  • destruction of epidermis and dermis
  • tissue death extends below sweat glands and hair
  • burning may involve fascia, muscle, and bone
  • Patient may be insensitive to pain immediately
    after due to destruction of nerve endings
  • Severe scarring

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  • Hairless areas palms, soles of feet, lips,
    nipples, some parts of genitalia
  • At approximately 6 months gestation fetus is
    covered with lanugo
  • After birth vellus hair replaces lanugo
  • At puberty terminal hair replaces vellus hair

Hair Growth
  • Growth begins when epidermal cells spread down
    into dermis to form a follicle
  • Follicle consists of 2 layers
  • Outer dermal root sheath
  • Epithelial root sheath (external internal
  • Follicles inner layer formed by stratum
  • Germinal matrix a cap-shaped cluster of cells at
    the bottom of the follicle
  • It is the cells of the germinal matrix that are
    responsible for forming hair/hair growth

Hair Anatomy
Skin Glands
  • Sweat glands - most common
  • Two types Eccrine apocrine
  • Based on location, secretion nervous system
  • Eccrine sweat glands - most numerous and wide
  • simple, coiled, tubular gland
  • Produces sweat or perspiration - a watery liquid
    rich in salts, ammonia, uric acid, urea and other
  • Sweat also plays an important role in maintaining
    constant body temperature
  • Majority found on soles of feet, palms, forehead
    and upper torso
  • 2. Apocrine sweat glands - larger than eccrine
  • located deep in the subcutaneous layer of the
  • Ex armpit (axilla), areola of breast, pigmented
    skin around anus
  • Ducts are connected to and secrete into hair
  • Classified as simple, branched tubular glands
  • Function of apocrine glands begins at puberty
  • Odor is from skin bacteria, not secretions

Sweat Glands
Sebaceous Glands
  • Secrete oil for hair skin
  • Simple alveolar gland found in dermal layer
  • Oil sebum
  • Lubricates skin
  • Antifungal property kills fungus bacterial
  • Increases effectiveness of surface film
  • Mostly associated with hair follicles
  • Glands activated at puberty
  • Stimulated by sex hormones
  • Accumulation of sebum in ducts white pimple
  • Oxidation causes sebum to darken blackhead

Ceruminous Glands
  • Modified apocrine sweat gland
  • Open into the skin of the external ear cannal
  • Brown waxy substance cerumen
  • Provides protection from dehydration
  • Risk for blockage and hearing loss

Mechanisms of Disease Skin Disorders
  • Skin Infections
  • Vascular Inflammatory Disorders
  • Abnormal Body Temperature
  • Skin Cancers

Skin Infections
  • Impetigo
  • Bacterial infection caused by either
    staphylococcus or streptococcus that usually
    occurs in young children
  • Reddish discoloration that develops into vesicles
    (blisters) and yellowish crusts
  • Can become systemic
  • Tinea fungal infection (ex ringworm, jock
    itch, athletes foot)
  • s/sx erythema (redness), scaling, crusting
  • Tx antifungal medications

Skin Infections
  • Warts caused by papillomaviruses
  • Usually benign, but can be malignant
  • Transmitted through direct contact
  • Tx freezing, drying, laser therapy
  • Boils (furuncles) local staphylococcus
  • Infection of hair follicles
  • Large, inflamed pus-filled lesions

Vascular Inflammatory Skin Disorders
  • Decubitus ulcers (bedsores)
  • Lesions caused by decreased blood flow to skin
    area usually on boney prominences
  • Tx changing position, soft surfaces
  • Urticaria (hives) raised red lesions (aka
  • Caused by leakage of fluid from blood vessels in
  • Causes severe itching
  • Usually due to allergic reaction, physical
    irritant or systematic disease
  • Scleroderma autoimmune disease affecting blood
    vessels and connective tissue of skin
  • Results in patches of yellowish, hardened skin

Vascular Inflammatory Skin Disorders
  • Psoriasis chronic inflammatory disease
  • Genetic basis
  • Cutaneous inflammation, followed by scaly lesions
  • Results from excessive rate of epithelial cell
  • Eczema most common inflammatory skin disorder
  • Inflammation, papules (bumps), vesicles
    (blisters), crusts
  • Usually s/sx of underlying condition
  • Ex allergic reaction or poison ivy

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Abnormal Body Temperature
  • Fever
  • Associated with systemic inflammatory release
  • Malignant hyperthermia
  • Abnormal rise in body temperature muscle
    rigidity when exposed to anesthetics or muscle
  • Heat exhaustion
  • Caused by fluid loss
  • Heat stroke
  • Inability to maintain normal body temp (gt105) in
    warm environments
  • Hypothermia
  • Inability to maintain normal body temp (lt95) in
    cold environments
  • Frostbite
  • Local damage to tissues from very low temperatures

Skin Cancer
  • Basal Cell Carcinoma
  • Most common type of skin cancer
  • Arises from stratum basale
  • Most common areas nose face
  • Usually occurs in patients gt 40 y/o
  • Rarely metastasizes

Skin Cancer
  • Squamous cell carcinoma
  • Slow growing arises from epidermis
  • Occurs in middle-aged elderly
  • Affects sun-exposed areas (scalp, forehead, backs
    of hands)
  • Some forms may metastasize

Skin Cancer
  • Malignant Melanoma
  • Most deadly of all skin cancers
  • Affects older individuals with light skin, eyes
    hair usually have poor ability to tan
  • May develop from pigmented mole
  • Use ABCD rule for detection
  • Asymmetrical
  • Benign moles symmetrical malignant moles
  • Border
  • Benign moles have distinct border malignant
    irregular/indistinct border
  • Color
  • Benign even color of brown malignant
    unevenly colored, mixture of shades
  • Diameter
  • Malignant diameter usually gt 6mm

Anthonys Textbook of Anatomy and Physiology 17th
Edition. Thibodeau, Gary A. PhD and Patton, Kevin
T. PhD. Mosby, Inc.
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