Cutaneous membrane or integument

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  1. Called cutaneous membrane or integument:

    1. Epidermis-

      1. Characteristics

        1. Stratified squamous epithelium

        2. Forms hair follicles and sebaceous glands

      2. Protective functions

        1. Shields moist under tissues from H2O loss

        2. When unbroken, keeps out harmful micro-organisms (bacteria)

      3. Stratum Basale: bottom layer of epidermis

        1. Constantly dividing & producing new cells that are pushed upward

        2. Blood supply is close but not in basale

        3. Langerhans cells: macrophages

          • Phagocytize microbes

          • Travel to lymphatic organs to stimulate immune system

        4. 3 pigments that color skin

          • Melanocytes: located in deeper epidermis & produced in hypodermis

            • produce melanin: pigment responsible for skin color

            • close to same # in everybody-close variation due to amount produced & distribution

            • produced to protect skin from UV rays - cause tanning &/or freckles

            • Albinism: lack of ability to produce melanin

              1. No pigment in skin, hair or eyes

          • Carotene – found in palms & soles of feet and causes yellowish hue in Asians

          • Hemoglobin – red blood cell causes pinkish hue to fair skinned people

      1. Stratum Corneum: top layer of epidermis

          • Pushed up from stratum basale

          • Become flattened & hardened

          • Keratinization causes hardening & waterproofing

            • Thickest in palms of hands & soles of feet

            • Waterproofing protects against water loss & gain

          • Loose blood supply, die & slough off

    1. Dermis- binds epidermis to subcutaneous

      1. Dense irregular connective tissue with collagenous and elastic fibers

      2. Blood vessels supply nutrients & wastes

      3. Nerve fibers - sensory receptors and motor fibers to send and receive impulses

      4. Hair shaft & sebaceous glands are deep within but covered by epidermis

      5. Sweat glands are located here & up through the epidermis

  1. Hypodermis: subcutaneous tissue- lies beneath the dermis

    1. Found between skin & underlying structures

      1. Loosely attached to muscle

      2. Directly attached to bone, if no muscle present

    2. Composed of loose connective tissue & adipose tissue

      1. Adipose stores energy & helps insulate the body

      2. Excess adipose results in obesity

  1. Accessory Organs

    1. Hair follicles

      1. Present on all surfaces except palms, soles, lips, nipples, and external reproductive organs

      2. Extends from the dermis which contains the root out to the surface of the epidermis

      3. Hair is epidermal cells which become keratinized and die as they grow up & out of the hair shaft

      4. Hair color is determined by the abundance of melanin in the epidermal cells that produce it.

        1. Lots of pigment gives dark hair, little gives blond, none gives white.

        2. Red hair requires special pigments

      5. Alopecia- hair loss or balding

        1. Androgenic- male baldness

        2. Alocecia areata- sudden onset of patchy hair loss: children & young adults

      1. Hirsutism: excessive body & facial hair in women caused by male hormone

      1. Hypertricosis – excesses hair growth all over the body (especially the face)

      1. Smooth muscle cells form the arrector pili muscle which attaches to the follicle and can cause the hair to stand on end when a person is upset or cold--thus “goose bumps”

    1. Nails

      1. Protective covering for the fingers and toes

      2. Epithelial cells become very hard by keratinization forming the nails

      3. The lanula at the base of the nail is the active growing region

      4. Pink hue from vascularized dermal tissue beneath nail bed

    1. Sweat Glands-sudoriferous glands

      1. Ceruminous gland- modified sweat glands produce cerumen (earwax)

      2. Two types of sweat glands-

        1. ) Apocrine glands

          • may act as a sex attractant

          • most open into hair follicles in the axillary region, anal region & groin

        1. ) Eccrine glands which control body temperature

          • secret out a pore –open onto surface of skin

          • excrete fluid made up of water, salts, urea & uric acid (wastes)

          • common at the head, neck and back

    1. Sebaceous Glands

      1. Associated with hair follicles

      2. Secrete oil , which keeps hair and skin soft, flexible, and waterproof

      3. Acne is caused from these being overactive and inflamed or clogged.

        1. White & blackheads

        2. When pus inducing bacteria- a boil or pimple results

        3. Acne vulgaris- inflammation of the sebaceous glands

    1. Mammary Glands-located in breasts

          • Results form complex hormonal changes occurring after childbirth

A 22-year-old woman sought medical care for a lesion in the plantar region of her left foot, a well-formed nipple surrounded by areola and hair. Microscopic examination of the dermis showed hair follicles, eccrine glands, and sebaceous glands. Fat tissue was noted at the base of the lesion. Clinical and histopathologic findings were consistent with the diagnosis of supernumerary breast tissue, also known as pseudomamma. To our knowledge, this is the first report of supernumerary breast tissue on the foot.

  1. Functions

    1. Regulation of body temperature

      1. High blood temperature signals nerve cells to stimulate sweat glands and dilate blood vessels


      1. Low blood temperature signals nerve cells to constrict sweat and blood vessels. If body temperature still falls, muscle activity is stimulated causing shivering

    1. Healing of wounds

      1. Inflammation - the area’s blood vessels become dilated and permeable, forcing fluids into the affected area. This provides oxygen and nutrients to promote healing.

      2. Epithelial cells divide rapidly, closing the wound

      3. If the injury affects the dermis or subcutaneous layers, blood clots form to stop bleeding, and a scab harden from the tissue fluids to cover and protect the area.

      4. Fibroblasts migrate and secret collagen fibers that bind the wound

      5. Macrophages remove the dead cells and debris

      6. The scab falls off revealing the underlying connective tissue, a scar

      7. (staying alive platelet coagulation)


      9. (wound stat band aid)

      10. (quick clot)


  1. Disorders of the skin

              1. Athlete’s foot- itchy, red & peeling skin

              1. Impetigo- oozing scabs

  • caused by bacterial infection

  • highly contagious

  • occurs most often in children

3. Psoriasis- skin develops pink or reddish patches covered by silver scales

  • caused by overactive cell division

  • chronic condition (possibly hereditary)

4. Eczema- red dry patchy areas

  • caused by sensitivity to various chemicals (detergents, soaps)

  • chronic condition (possibly hereditary)

5. Dandruff- flaking & itching scalp

  • NOT caused by dry scalp

  • caused by accelerated rate of keratinization in certain areas of scalp

6. Urticaria- hives: appearance of reddish, elevated patches & often by itching

  • caused by allergic reaction

7. Shingles- similar look to Urticaria (hives) but nerves in skin are highly sensitive & painful

  • caused by the chicken pox virus

8. Warts are due to viral infection

9. Moles are not usually cancerous- caused by overgrowth 9. Moles are not usually cancerous- caused by overgrowth of melanocytes

10. Skin cancer- unrestrained cell division of the skin

A. Nonmelanoma cancers- much less likely to metastasize (cancer cells normally do NOT break off from initial tumor & start new tumors elsewhere)

1. Basal cell carcinoma- most common type of skin cancer

* Begins when UV radiation causes epidermal basal cells to form tumor

* Suppresses the immune’s system ability to detect the tumor

* Signs of basal cell carcinoma:

- open sore that will not heal

- recurring reddish patch

- smooth, circular growth w/ raised edge

- shiny bump or pale mark

* 95% patients easily cured by removal of tumor, but recurrence if common

2. Squamous cell carcinoma- begins in epidermis proper

* 5x more common than basal cell

*More likely to spread to nearby organs

*Death occurs about 1% of cases

*Signs are same for basal cell but also show by a wart that bleeds & scabs

Shave biopsy is adequate to obtain diagnosis of basal or squamous cell carcinoma.

Nevoid basal cell carcinoma (Gorlin) syndrome

    Nevoid basal cell carcinoma (NBCC) syndrome is an autosomal dominantly inherited syndrome in which patients have numerous (often hundreds) of BCCs. These occur at a young age (onset is typically in the second decade) and are usually very small. They may resemble benign skin tags.

    The condition is due to a chromosomal defect on 9q31 such that all cells of affected individuals carry one defective copy of the gene. Damage (solar, ionizing radiation, spontaneous mutation) to the other chromosome of the pair leads to development of BCC

B. Melanoma cancers- most likely to be malignant (ability to kill)

*Appears as unusual mole- spilled ink spot or different shades of color

*Mole may itch, hurt or feel numb

*Skin around mole turns grey, white or red

*Most common in fair skinned persons, especially if they had many sunburns

*Risk increases with the number of moles

  1. Asymmetry

  2. Border irregularity

  3. Color

  4. Diameter greater than ¼”

Why do you think cases of melanoma have doubled in the last decade?

II. Burns

*Caused by heat, radioactive, chemical or electrical agents

*Burn severity due to depth & extent of burned area

*Estimating extent of burn is called “rule of nine” see fig 5.8

  1. First-degree (partial thickness burn) - depth of only epidermis

  • Redness & pain but NO blistering

  • Moderate sunburn

  • Pain subsides in 48-72 hrs, no scarring & skin peels in about 1 week

  1. Second-degree (partial thickness burn) - all of epidermis & into part of dermis

  • Redness & pain + blisters

  • The deeper the burn, the more blisters

  • If not infected, heals w/little scarring in 10-14 days

  • If deep into the dermis, heals slower in 30-105 days & scarring is common

3. Third-degree (full thickness burn) - destroys entire thickness of skin

  • Surface of wound is leathery & may be brown, tan, black, white or red

  • NO pain because pain receptors destroyed

  • Also all accessory organs are destroyed

4. Fourth-degree burn – tissue down to the bone

  • Chances of survival are not good unless very limited area if affected

5. Concerns

  • Fluid loss - counteracted by IV of salt solutions

  • Heat loss – minimized by warm environment

  • Bacterial infection – treated by isolation & antibacterial dressing

  1. Treatments

  • Damaged tissue removed

  • Skin grafting is started

-autografting: skin taken from another area of self-

*preferred because rejection rate is very low

*if extensive, skin can be grown from self cells

-hetrografting- skin taken from another person

Extensive burns of the lower limb. The size of the defect called for a mesh graft, produced by harvesting split-thickness skin grafts and meshing them, using a skin graft expander to allow a larger surface to be covered.

III. Effects of aging (know at least 5)

1. Epidermis still thick but division decreases

2. Dermis becomes thinner

3. Papillae flatten

4. Epidermis held less tightly to dermis (skin looser)

5. Adipose tissue decreases in face & hands

6. Collagenous fibers become coarser, thicker & further apart

7. Elastic fibers in upper dermis are lost; thicker, less elastic and disorganized in lower


8. Homeostatic adjustment to heat is limited

-decreased vasculature (fewer blood vessels)

-fewer sweat glands

9. Number of hair follicles decrease (thinning hair)

10. Reduced sebaceous glands-skin cracks

11. Melanocytes reduced- hair turns gray & skin paler

12. Remaining melanocytes are larger & pigmented blotches appear

13. Many of these changes due to UV radiation (sun!)

-rough skin, mottled pigmentation, fine lines & wrinkles, deep furrows, numerous

benign skin growths & skin cancer

IV. Homeostasis

1. Functions of skin

- protective barrier:

*safeguarding from physical trauma

*bacterial invasion

-melanocytes: UV radiation

-sebaceous glands: acidic to retard growth of bacteria

-Langerhans cells- phagocytize pathogens & alerts immune system

2. Regulates water loss- because thick, dead & keratinized (waterproof)

-limits water from entering body in immersion

-assists urinary system by sweat glands excreting some urea

3. Produces vitamin D

`-useful to digestive & skeletal systems

  1. Gathers sensory information

-specialized for touch, pressure, pain, hot & cold

-fingertips greatest number

4. Regulates body temperature

-when body gets too hot

*releases heat from ATP release

*blood vessels dilate to bring blood to surface to cool

*sweat absorbs heat & is carried away when evaporates

-when body gets too cold

*sweat glands remain inactive

*blood vessels constrict

*muscles contract to cause shivering (arector pili muscle =goosebumps)

*frostbite-skin dies from blood flow restriction for extended period

5. Body’s regulatory system fails

-hyperthermia: body temp above normal

*blood pressure low & salts lost from excessive sweating

*heat stroke- temp up to 110’F & no sweating

*fever- special hyperthermia brought about by bacterial infection; fever

“breaks” & sweating occurs to normal set point

-hypothermia: body temp below normal

*90’-95’: uncontrollable shivering, incoherent speech & lack of coordination

*80-90’: pulse rate slows, hallucinations occur as unconsciousness develops

Breathing becomes shallow; shivering diminishes as rigidity sets in

50% mortality
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