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Chapter 6: Integumentary System

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  • Chapter 6: Integumentary System

  • 6.1 Introduction

    Why is skin considered to be an organ?

    What makes up the integumentary system?

  • Integumentary System

    Skin (cutaneous membrane)

    Skin derivatives

    Sweat glands

    Oil glands



  • 6.2 Skin and its Tissues

    Skin is also know as a cutaneous membrane

    How is the skin vital in maintaining homeostasis?

    Skin has 2 layers Epidermis: most superficial; thin; stratified

    squamous epithelial tissue; keratinized

    Dermis: deep to epidermis; thicker; loose and dense connective tissue; contains appendages (hair, glands, blood vessels, nerves, etc)

    Subcutaneous layer or hypodermis – lies deep to dermis; consists mostly of loose adipose connective tissue

  • Skin Structure

    Figure 4.3

  • Epidermis – composed of keratinized stratified squamous epithelium. Structure: Principle Cell types and layers

    Keratinocytes – makes up 90%, arranged in 4 to 5 layers, produce:

    Keratin: tough, fibrous, waterproof protein

    Lamellar granules: repel water

    Melanocytes – 8%, produces pigment melanin, have long slender projections that transfer melanin to keratinocytes

    Melanin: brown/black pigment, absorbs UV light

    Langerhans cells – aid in immune response; easily damaged by UV light

    Merkel cells – contact sensory neuron, aid in sensation

    A Closer look at the Epidermis

  • Epidermal Cell layers (deepest to most superficial)

    Stratum basale (deepest or base layer) – attached to basement membrane, contains most of the melanocytes, has cuboidal or columnar cells, mitosis.

    Stratum spinosum (spiny layer) – 8-10 layers of irregular shaped keratinocytes, become flattened

    Stratum granulosum (granular layer) – 3 - 5 layers of flat keratinocytes, undergoing cell death

    Stratum lucidum (clear layer) – dead cells w/ lots of keratin; only in thick skin of finger tips, palms and feet

    Stratum corneum (most superficial, horny layer) – 25 to 30 layers of flattened dead cells containing keratin, continuously shed and replaced by cells from deeper strata

    What is Keratinization?

  • Melanin

    Pigment (melanin) produced by melanocytes

    Melanocytes are mostly in the stratum basale

    Color is yellow to brown to black

    Amount of melanin produced depends upon genetics and exposure to sunlight

  • Normal Skin Color Determinants


    Yellow, brown, or black pigments


    Orange-yellow pigment from some vegetables


    Red coloring from blood cells in dermal capillaries

    Oxygen content determines the extent of red coloring

  • Functions of epidermis

    Protection (damage, UV rays, etc)

    Growth / Repair (regeneration)

    Immune response


    Water-repellent & sealant

    Epidermal growth and repair

    Regeneration time for skin is about 35 days

    Shortened regeneration time results in increased thickness of stratum corneum making a callus (thick skin)

  • Dermis: deep to the epidermis

    Structure of Dermis

    Much thicker than epidermis has 2 portions:

    Papillary Dermis (Superficial part of dermis): Loose areolar connective tissue

    Dermal Papillae: finger-like projections indenting epidermis; increase surface area

    Contain capillaries

    Contain corpuscles of touch (Meissner corpuscles)

    Reticular Dermis (Deep part of dermis): dense connective tissue

    Contains hair follicles, nerves, blood vessels, sebaceous (oil) glands, & sudoriferous (sweat) glands

    A Closer look at the Dermis

  • Functions of the Dermis


    Strength / support

    Stretchable / elasticity


    Dermal growth & repair

    Dermis does not continually shed and regenerate like epidermis

    If this layer is damaged, the fibroblasts form a dense mass of connective fibers forming a scar

    Extreme stretching may produce small tears causing striae or stretch marks

  • Skin Structure

    Subcutaneous tissue (hypodermis) is deep to dermis

    Not part of the skin

    Anchors skin to underlying organs

    Composed mostly of adipose tissue

  • Sebaceous (oil) glands

    Secretes oil (sebum), keeps hair & skin soft/pliable, prevents water loss from skin

    Located in dermis, except for palms & soles

    Aids in formation of pimples & black heads

    2 types of Sudoriferous (sweat) glands

    Eccrine glands –.

    Apocrine glands –


  • Appendages of the Skin

    Sebaceous glands

    Produce oil

    Lubricant for skin

    Prevents brittle hair

    Kills bacteria

    Most have ducts that empty into hair follicles; others open directly onto skin surface

    Glands are activated at puberty

  • Appendages of the Skin

    Figure 4.6a

  • Appendages of the Skin

    Sudoriferous (sweat) glands

    Produce sweat

    Widely distributed in skin

    Two types


    Open via duct to pore on skin surface

    most common; secretes sweat, eliminates wastes, maintains core temp


    Ducts empty into hair follicles

    activated during puberty, located in armpit, groin, beard.

  • Appendages of the Skin

    Figure 4.6b

  • Sweat and Its Function

    Composition Mostly water

    Salts and vitamin C

    Some metabolic waste

    Fatty acids and proteins (apocrine only)

    Function Helps dissipate excess heat

    Excretes waste products

    Acidic nature inhibits bacteria growth

    Odor is from associated bacteria

  • Appendages of the Skin

    Ceruminous glands

    Located in ear canal

    Produces ear wax (cerumen)

    Too much wax can cause a blockage of ear canal, loss of hearing

  • Appendages of the Skin

    Hair follicles – composed of epithelial cells, distributed all over body except for palms, anterior side of fingers, soles, genitalia, and lips

    Dermal and epidermal sheath surround hair root

    Genetics and hormones determine thickness and distribution of hair

    Hair is also important for protection and reproduction

    Melanocytes provide pigment for hair color

    Arrector pili muscle

    Smooth muscle

    Pulls hairs upright when cold or frightened (goose bumps)

  • Appendages of the Skin

    Figure 4.7c

  • Appendages of the Skin

    Hair anatomy

    Central medulla

    Cortex surrounds medulla

    Cuticle on outside of cortex

    Most heavily keratinized

    Figure 4.7b

  • Appendages of the Skin

    Figure 4.7a

  • Appendages of the Skin

    Figure 4.8

  • Appendages of the Skin

    Nails – Plates of tightly packed, hard, keratinized cells of epidermis

    Very protective of ends of fingers; aids in grasping and manipulating small objects; scratching

    Stratum basale extends beneath the nail bed

    Responsible for growth

    Lack of pigment makes them colorless

  • Appendages of the Skin

    Nails can indicate health issues

    Bluish nail beds may indicate circulation issue

    White nail bed or oval depressions can indicate anemia

    Pigmented spot (not injury) can indicate melanoma

    Horizontal furrows may indicate period of illness or malnutrition

    Disorders of heart, liver, or lungs may cause extreme curvature of nails

    Red streaks in nails may be traced to RA, uclers, or hypertension

  • Nails: Figure 6.4

    Free edge – extends past end of finger

    Nail plate / body – visible part of nail

    Nail root – sides and bottom of nail in groove, hidden by cuticle

    Nail bed – skin surface that is covered by nail plate

    Cuticle – skin around bottom of nail (stratum corneum)

    Lunula – half-moon shaped white area at base of nail; the most active growing region

    average growth is 0.5 to 1 mm per week

  • Appendages of the Skin

    Figure 4.9

  • Skin Functions

    Table 4.1 (1 of 2)

  • Skin Functions

    Table 4.1 (2 of 2)

  • Overall Functions of the Integumentary System

    Regulation of body temperatures


    Excretion and absorption

    Vitamin D synthesis


    Barrier to microorganisms

    Barrier to chemical hazards

    Reduces injury to underlying structures

    Prevents dehydration

    Protects (via melanin) excessive UV exposure

    Surface film – protective barrier over skin’s surface; (like wax on your car)

  • 6.4 Regulation of Body Temp.

    How does your skin aid in regulating body temperature?

    What portion of the brain controls the set point for body temperature?

    Differentiate between hypothermia and hyperthermia. Discuss the consequences of each.

  • 6.5 Healing of Wounds

    What is inflammation? Is it normal or abnormal and why?

    Differentiate between the healing processes of a superficial wound and a deeper wound. Which one would result in a scar?

  • Skin Homeostatic Imbalances


    Athlete’s foot (tinea pedis)

    Caused by fungal infection

    Itchy, red, peeling condition of skin between the toes

    Boils and carbuncles

    Caused by bacterial infection

    Common on dorsal neck, inflammation of hair follicles and sebaceous glands.

    Cold sores

    Caused by virus (herpes simplex) – activated by stress, fever, illness, and UV Radiation

    Small fluid-filled blisters that itch and sting

  • Homeostatic Imbalances

  • Skin Homeostatic Imbalances

    Infections and allergies

    Contact dermatitis

    Exposures cause allergic reaction

    Itching, redness, and swelling of skin – progressing to blistering


    Caused by bacterial infection

    Pink, water-filled, raised lesions (nose and mouth) that develop a yellow crust and eventually rupture


    Cause is unknown

    Triggered by trauma, infection, stress

    Overproduction of skin cells, reddened epidermal lesions covered with dry, silvery scales that itch, burn, crack and sometimes bleed.

  • Skin Homeostatic Imbalances

    Figure 4.10

  • Skin Homeostatic Imbalances


    Tissue damage and cell death caused by heat, electricity, UV radiation, or chemicals

    Associated dangers


    Electrolyte imbalance

    Circulatory shock

  • Rule of Nines

    Way to determine the extent of burns

    Body is divided into 11 areas for quick estimation

    Each area represents about 9% of total body surface area

  • Rule of Nines

    Figure 4.11a

  • Severity of Burns First-degree burns

    Only epidermis is damaged

    Skin is red and swollen

    Second-degree burns

    Epidermis and upper dermis are damaged (partial-thickness burn)

    Skin is red with blisters

    Third-degree burns

    Destroys entire skin layer (full-thickness burn)

    Burn is gray-white or black

  • Severity of Burns

    Figure 4.11b

  • Critical Burns

    Burns are considered critical if

    Over 25% of body has second-degree burns

    Over 10% of the body has third-degree burns

    There are third-degree burns of the face, hands, or feet

  • Skin Cancer

    Cancer—abnormal cell mass

    Classified two ways


    Does not spread (encapsulated)


    Metastasized (moves) to other parts of the body

    Skin cancer is the most common type of cancer

  • Skin Cancer Types

    Basal cell carcinoma

    Least malignant – 99% cure in which lesion is removed surgically

    Most common type – Sun Exposure

    Arises from stratum basale – cells are altered so that they cannot form keratin

    They invade dermis and subcutaneous tissue

    Symptoms: shiny, dome-shaped nodule that later develop a central ulcer with a “pearly” beaded edge.

  • Skin Cancer Types

    Figure 4.12a

  • Basal Cell Carcinoma

  • Skin Cancer Types

    Squamous cell carcinoma

    Metastasizes to lymph nodes if not removed

    Early removal allows a good chance of cure

    Believed to be sun-induced

    Arises from stratum spinosum

    Symptoms: lesion, scaly, reddened papule (small, rounded elevation), that gradually forms a shallow ulcer with a firm, raised border.

    Grows rapidly and metastasizes to adjacent lymph nodes if not removed

    If caught early and removed surgically or by radiation – the cure rate is good.

  • Squamos Cell Carcinoma

  • Skin Cancer Types

    Figure 4.12b

  • Skin Cancer Types

    Malignant melanoma

    Most deadly of skin cancers

    Cancer of melanocytes

    Metastasizes rapidly to lymph and blood vessels

    Detection uses ABCD rule

    Cause: Genetics, accumulated damage to DNA in skin cells

    Symptoms: arise as a spreading brown to black patch that metastasizes rapidly to surrounding lymph and blood vessels

    Chance of survival is 50%

    Accounts for 5% of skin cancers

  • Skin Cancer Types

    Figure 4.12c

  • Malignant Melanoma

  • ABCD Rule A = Asymmetry

    Two sides of pigmented mole do not match

    B = Border irregularity

    Borders of mole are not smooth

    C = Color

    Different colors in pigmented area

    D = Diameter

    Spot is larger then 6 mm in diameter

    E = Elevation/Evolves

    Spot is elevated or changes over time