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Chapter 5 The Integumentary System The largest organ in the body (~18 sq. feet)

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  • Chapter 5

    The Integumentary System

    The largest organ in the body

    (~18 sq. feet)

  • Cool facts about the skin

    There are approximately 19,000,000 skin cells on every square inch of your body

    Millions of skin cells are rubbed off daily

    You have over 2 million sweat glands

    All sweat gland tubules in the body would stretch into 6 miles of tubes

    Amount of sweat can vary from 100 to 8,000 mL/day

    Fastest growing hair is the beard

  • Functions of the skin


    barrier between the internal and external environment

    Water Proofing and prevents water loss

    Regulates body temperature


    nerve endings that react to heat, cold, touch, pressure, vibration, and tissue injury

  • More functions.


    Through perspiration

    Production of Vitamin D

    Insulation and Cushion

    Contributes to skin color - Melanin

  • Skin Layers

    Superficial to Deep

    Epidermis Stratified squamous

    Contains no blood vessels

    Dermis Dense Irregular CT

    Contains blood vessels

    Hypodermis Adipose

    Contains blood vessels

  • Epidermis


    Outermost layer of the skin

    Several strata (layers)

    Thinnest on the eyelids (0.05 mm )

    thickest on the palms and soles (1.5 mm)

    Avascular (no blood supply)

    Stratified squamous

  • Strata of Epidermis

    (superficial to deep)

  • Come Lets Get Sun Burned

  • Stratum Corneum

    25 30 rows dead plate-like envelopes filled with keratin that have migrated up underlying layers

    Cells are worn/sloughed off daily (desquamation)

    Total new epidermis every 35-45 days

    Flattened and hardened cells

    Contain Keratin (Keratinocytes or K-Cytes) Keeps skin elastic and protects underlying cells from drying out

    Barrier against microbe invasion

  • Stratum Lucidum

    3 5 rows of dead K-cytes

    As K-cytes are pushed up they get bigger and flatter and adhere together, and then eventually become dehydrated and die

    Found in thick skin areas

    palms, soles and elbows

    Not found in thin skin areas


  • Stratum Granulosum

    3 5 rows

    Aka: granular layer

    have lost their nuclei and are characterized by dark clumps (grains) of cytoplasmic material.

    Begins the process of keratinization

  • Stratum Spinosum

    8 10 rows of actively dividing K-cytes

    Spiny or prickly appearance

    Cells interlock to support the skin

  • Stratum Basale

    Aka: basal cell layer

    Deepest layer

    One cell thick, rests on the basement membrane

    Dividing continuously As new cells form older ones are pushed up towards the skin

    Nutrients received from dermis below

  • Four Types of cells found in Epidermis

    Cell type Where found Function

    Keratinocytes All 5 layers Produce keratin Strength Waterproofing


    S. Basale Produce melanin (same # in all people skin color determined by amount of melanin produced)

    Merkel cells (tactile cells) S. Basale Involved with touch reception

    Langerhans Cells S. Basale Immune cells that eat bacteria and foreign debris

  • Dermis

    Composed of 2 regions

    Papillary region

    Reticular layer


    Has many blood vessels

    Sensory nerves

  • Papillary region

    Dense Irregular CT

    Contains Dermal Papilla projections into papillary region that extend into and anchor the epidermis

    Form fingerprints and footprints

    Contain capillaries that nourish the epidermis

    Contains Meissners Corpuscles (sensory touch receptors)

  • Reticular Layer

    Dense Irregular CT

    Collagen fibers strength and flexibility

    Elastic fibers stretchable (maintain skin tension)

    Contains Pacinian Corpuscles sensory receptors for deep pressure

  • Hypodermis AKA: subcutaneous tissue

    Loose CT Adipose


    Storage of energy


    Contains lymph vessels


    Protective padding

    Excessive adipose = obesity

  • Accessory Structures of the Skin

    Hair, nails, and glands

    Originates in the Epidermis

    Extends into the dermis

  • Hair

    Everywhere except palms, soles, lips, nipples, portions of external reproductive organs

    Stronger hair in the scalp region

    Puberty: Axillary and pelvic hair growth in both sexes

    Beard growth in males

    Hirsutism-excess male sex hormone in females

  • Hair Growth

    Hair grows from hair follicles

    Follicle cells divide continuously

    pushed up and away from nutrients

    Keratinized and die eventually


    Eyelash 3-4 months

    Scalp 3-4 years

  • Hair Follicle and Associated Parts

    Hair follicle: Root-portion within the follicle

    Shaft-portion beyond the follicle

    Sebaceous glands (oil glands) 1 or more per hair

    Arrector pili (smooth muscle) Attached to follicle

    Contraction causes goose-bumps

  • Hair Follicle and Associated Parts (Fig 5.1 and 5.2)

  • Nails

    Nail root-special epithelial cells from which nails growth

    Nail body-visible part of the nail

    Cuticle-skin fold that hides the nail root

    Lunula- whitish half moon Thicker layer of rapidly producing cells

    Nail bed-area of dermis on which nail grows

  • Nail Growth

    Nails grow over the nail bed


    About 1mm growth per week

    Pink color because of vascular dermis below

  • Nail Anatomy (Fig 5.3)

  • Sweat Glands

    AKA: Sudoriferous glands

    Two types



  • Sweat Glands

    Apocrine Eccrine

  • Sweat Glands



    Duct leads to hair follicle

    Deeper in dermis

    More abundant in the axillary region

    Thicker/viscous sweat


    Duct lead directly to surface of skin

    watery sweat

    Found all over body

    Ceruminous glands modified sweat gland found in ear (secrete earwax or cerumen)

  • Sebaceous Glands

    Associated with a hair follicle

    Secrete Sebum Oily (lipid) substance

    Flows into the follicle then out to the skin surface

    Lubricates hair and skin


    Weakens and kills bacteria

  • Mammary Glands

    Modified apocrine glands

    secrete milk after childbirth

  • Skin Disorders

    Athletes Foot Fungal infection that involves soles and toes of feet

    Impetigo Infectious disease caused by a bacterial infection that results in pustules that crust over.

    Psoriasis chronic condition causing skin to develop reddish patches covered by silvery scales. Due to over active cell division.

  • Disorders Continued

    Eczema an inflammation of the skin caused by sensitivity to various chemicals

    Dandruff caused by an over accelerated rate of keratinization in certain areas of the scalp.

    Urticaria (Hives) is allergenic reaction characterized by the appearance of reddish, elevated patches and often itching.

  • Athletes Foot

  • Impetigo

  • Psoriasis

  • Eczema

  • Dandruff*&um=1

  • Urticaria

  • Skin Cancer


    Basal Cells and Squamous


    Less likely to metastasize

    Usually found at sun

    exposure spots


    Begins in Melanocytes

    Example unusual moles

    More likely to metastasize

  • Wound Healing 1. Puncture wound fill with blood

    2. Chemicals released by damaged tissue cause blood to clot.

    3. Clotting prevents pathogens and toxins from spreading.

    4. Scab develops

    5. Fibroblasts Help with tissue regeneration

    Basal Layer begins to form new cells

    WBC Fight infection

    Scar collagen fibers arranged to provide maximum strength, devoid of feeling

  • Burns Two factors affect burn severity: Depth & Extent

    First Degree Burns

    Only Epidermis

    redness and pain, but no blisters

    Ex. Moderate Sunburn

    Second Degree Burns

    Entire Epidermis & Part of Dermis

    Blistering can occur

    Ex. Severe Sunburn

  • Burns Continued

    Third Degree Burns Full thickness burns, destroys the entire thickness of the skin

    Fourth Degree Burns - Involves tissue down to the bone.*&sa=N&um=1 of Burn.htm&usg=__CxaciqNohMNt6FNkDi3LnxADV-w=&h=1200&w=1792&sz=702&hl=en&start=6&um=1&tbnid=sF0TWD9UIAW9VM:&tbnh=100&tbnw=150&prev=/images?q=Fourth++Degree+skin+burns&hl=en&*&sa=G&um=1

  • Effects of Aging on Skin Layers

    Epidermis: Maintains its thickness

    Decrease in the rate of cell mitosis

    Is held less tightly to the dermis (looser skin)

    Dermis: dermal papillae flatten

    Dermis becomes thinner

    Hypodermis: Decrease in the adipose tissue of face and hands (older

    people feel cold)

  • Effects of Aging on Fibers in the Dermis

    Collagen Fibers

    Collagenous fibers become coarser, thicker, and farther apart

    Overall less collagen than before

    Elastic Fibers

    Elastic fibers in the upper layer are lost

    Elastic fibers in the lower dermis become thicker, less elastic, and disorganized

  • Why is there wrinkling of skin with age?

    Epidermis is loose

    Fewer and more disorganized fibers in the dermis

    Less padding in the hypodermis

  • Aging and Homeostasis

    Limited adjustment to heat due to: less vasculature (fewer blood vessels)

    Fewer sweat glands

    Decrease in the number of hair follicles Thinning of hair on scalp and extremities

    Decreased number of melanocytes (gray hair and paler skin)

    Some pigment cells get larger-blotches

    Decrease in the number of sebaceous glands Cracking of skin

  • Aging and Sun Damage (UV radiation)

    Roughened skin

    Uneven pigmentation

    Fine lines, wrinkles, and deep furrows

    Benign skin growth

    Skin cancer

  • Skin and Homeostasis


    Regulation of water loss

    Waste elimination (assists Urinary System)

    Production of Vitamin D

    Gathering of Sensory Information

    Body Temperature regulation

  • Skins Protective Functions

    Protective covering around the body against physical trauma and pathogens

    Melanocytes protect against UV radiation

    Outer keratinized cells prevent bacterial invasion

    Oily (acidic) secretions from sebaceous glands prevents bacterial growth

    Langerhans cells phagocytize pathogens and alert immune system

  • Regulation of Water Loss

    Waterproofing by outer keratinized cells

    Prevention of excess water entry into the skin by keratinized cells

  • Skin and Waste Elimination

    Sweat glands allow perspiration

    Sensible perspiration-can be felt

    Insensible perspiration-without awareness

    Perspiration contains


    Small amounts of salt, ammonia, urea, and other wastes

  • Skin and Vitamin D Production

    Vitamin D production in skin cells with the help of UV

    Small amount of UV needed

    Vitamin D (skin) goes to the

    Liver and Kidneys secrete

    Calcitrol (hormone)circulates and regulates calcium and phosphorus levels

    Vitamin D helps prevent rickets (soft/deformed bones)

  • Skin and Sensory Information

    Sensory receptors in the epidermis and dermis

    Sense touch, pressure, pain, hot, and cold

    Greatest number of touch receptors in the fingertips!

  • Skin and Regulation of Body Temperature (97F-100F)

    Increase in body temperature:

    Dilation of blood vessels in the skin

    Increase in the amount of blood brought to skin

    Sweat glands become more active

    Evaporation leads to skin cooling

    Decrease in body temperature: opposite effect

    Shivering-due to muscle contractions, heat production

    Arrector pili muscles contract-goose bumps

    Frostbite-severe restriction of blood flow, dead skin

  • Hyperthermia- Body Temp. Above Normal

    Heat Exhaustion: Low BP, excessive sweating (salt loss), high body temperature

    Heat stroke: high body temperature (110F), no sweating

    Fever: high body temperature due to immune response and bacterial infection

  • Hypothermia-Body Temperature below Normal

    90-95F: Uncontrollable shivering

    Incoherent speech, Lack of coordination

    Low pulse rate

    below 80-85F: Hallucinations or unconsciousness

    Shivering diminishes, rigidity sets in

    50% mortality