Integumentary System

Consists of:

  • skin (cutaneous membrane)

  • skin appendages- sweat glands, oil glands, hair, nails

Structure and Function of Skin: Skin Layer and Diagram


Functions:

  • insulates and cushions deeper body organs

  • protects the body from mechanical damage, chemical damage, thermal damage, chemical damage, thermal damage, UV, radiation, microbes, desiccation (drying out)

  • aids in loss of retention of body heat as controlled by the nervous system (thermoregulation)

  • aids in excretion of urea and uric acid

  • synthesizes Vitamin D

2 kinds of tissue compose the skin

  • epidermis

  • dermis

Hypodermis (subcutaneous layer)

  • anchors skin to underlying organs

  • not technically part of the integumentary system

  • composed mostly of adipose tissue

  • serves as a shock absorber and insulates deeper tissues

Epidermis- outer layer

  • capable of being hard and tough

  • stratified squamous epithelium

  • Keratinocytes (the most common cell) produce a fibrous protein called Keratin

  • Avascular

  • composed of 5 layers (strata) deepest to top layers:

    • Stratum Basale

    • Stratum Spinosum

    • Stratum Granulosum

    • Stratum Lucidum (thick, hairless skin only)

    • Stratum Corneum

Structure and Function of Skin: Skin Layer and Diagram

Stratum Basale (stratum germinativum)

  • deepest layer of epidermis

  • lies next to dermis

  • wavy borderline with the dermis anchors the two together

  • cells undergoing mitosis

  • daughter cells are pushed upward to become the more superficial layers

Stratum Spinosum

  • cells become increasingly flatter and more keratinized

Stratum Granulosum

  • filled with keratin; cells begin to die after SG

Stratum Lucidum

  • formed from dead cells of the deeper strata

  • occurs only in thick, hairless skin of the palms of the hand and soles of the feet

Stratum Corneum

  • outermost layer of epidermis

  • shingle-like dead cells are filled with keratin (protective protein prevents water loss from skin)

Epidermal Dendritic Cells

  • alert and activate immune cells to a threat (bacterial or viral invasion)

Merkel Cells

  • associated with sensory nerve endings

  • serve as touch receptors called Merkel discs

Dermis

  • connective tissue

  • underlies the epidermis

  • 2 layers

    • Papillary layer (upper dermal region) contain projections called dermal papillae

      • indents the epidermis above

      • many projections contain capillary loops, and others house pain and touch receptors

      • on palm and sole surfaces, papillae increase friction and gripping ability

      • fingerprints are identifying films of sweat

    • Reticular layer (deepest skin layer)

      • blood vessels

      • sweat and oil glands

      • deep pressure receptors (lamellar corpuscles)

  • other dermal features

    • cutaenous sensory receptors

    • phagocytes

    • collagen and elastic fibers

    • blood vessels

Skin color

  • 3 pigments contribute to skin color

    • Melanin

      • yellow, reddish brown, or black pigments

      • pigment produced by melanocytes

      • Melanocytes mostly in the stratum basale of the epidermis

      • accumulates in membrane-bound granules called melanosomes

      • amount of melanin produced depends upon genetics and exposure to sunlight

      • eumelanin (darker) and pheomelanin (Red/pink)

    • Carotene

      • orange-yellow pigment from some vegetables

    • Hemoglobin

      • red coloring from blood cells in dermal capillaries

      • oxygen content determines the extent of red coloring

Skin color (not permanent)

  • Redness (erythema)- due to embarrassment, inflammation, hypertension, fever, or allergy

  • Pallor (blanching)- due to emotional stress (such as fear), anemia, low blood pressure, impaired blood flow to an area

  • Jaundice (yellow cast)- indicates a liver disorder

  • Bruises (black and blue marks)- hematomas

  • Cyanosis (blue/grey)- severe lack of oxygen

Appendages of the skin

  • cutaneous glands are all exocrine glands

    • sebaceous glands (oil glands)

      • located all over skin except for palms and soles

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

      • glands are activated at puberty

      • produce sebum (oil)

        • makes skin soft and moist

        • prevents hair from becoming brittle

        • kills bacteria

        • increased amounts due to androgens in adolescents

    • sweat glands

  • hair and nail follicles

  • nails

  • sweat (sudoriferous) glands

    • produce sweat

    • widely distributed in skin

    • 2 types

      • Eccrine (everywhere) glands- cool you

        • open via duct to sweat pores on the skin’s surface

        • produce acidic sweat (water, salts, vitamin C, traces of metabolic waste)

        • function in body temperature regulation (thermoregulation)

      • Apocrine glands- show up at puberty

        • ducts empty into hair follicles in the armpit and genitals

        • begins to function at puberty

        • release sweat that also contains fatty acids and proteins (milky or yellowish color)

        • play a minimal role in body temperature regulation

        • active during pain, sex, stress

Homeostatic Imbalance of Sebaceous Gland

  • acne= infection of the gland

  • blackhead= dried blackened sebum; blocked gland

  • whitehead= same, not blackened

  • seborrhea= cradle cap in infants; overactive glands

Hair

  • produced by hair follicle

  • root is enclosed in the follicle

  • shaft projects from the surface of the scalp or skin

  • consists of hard keratinized epithelial cells

  • melanocytes provide pigment for hair color

  • hair grows in the matrix (mitosis) of the hair bulb in stratum basale

Associated hair structures

  • hair follicle

    • dermal region provides a blood supply to the hair bulb (deepest part of the follicle)

    • Arrector pili muscle connects to the hair follicle to pull hairs upright when we are cold or frightened

If the hair shaft is oval, the hair will be smooth, silky, wavy.

If the hair shaft is flat and ribbonlike, the hair is curly or kinky.

Nails

  • heavily keratinized, scalelike modifications of the epidermis

  • stratum basale extends beneath the nail bed, which is responsible for growth

  • lack of pigment makes nails colorless

Parts of a nail

  • free edge- end of nail, tip

  • stratum basale beneath nail is nail bed

  • Body is the visible attached portion

  • Nail folds are skin folds that overlap the edges of the nail; the cuticle is the proximal edge

  • Root of nail is embedded in skin

  • growth of the nail occurs from thickened proximal nail matrix

Infections to know

  • Athlete’s Foot- caused by fungal infection, itchy red peeling skin between the toes

  • Boils (furuncles) and carbuncles- caused by inflamation of hair follicles, carbuncles are clusters of boils caused by bacteria

  • Cold Sores (fever blisters)- caused by human herpesvirus 1, blisters itch and sting

  • Contact dermatitis- caused by exposure to chemicals that provoke allergic responses, itching redness and swelling of the skin

  • Impetigo- caused by bacterial infection, pink fluid-filled raised lesions around mouth/nose

  • Psoriasis- triggered by trauma, infection, hormonal changes, or stress, red epidermal lesions covered with dry silvery scales that itch burn crack or sometimes bleed

Burns

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

  • associated dangers

    • protein denaturation and cell death

    • dehydration and electrolyte imbalance

    • circulatory shock

  • result in loss of body fluids and infection from the invasion of bacteria

  • extent of a burn is estimated using the rule of nines

    • body is divided into 11 areas for quick estimation

    • each area represents about 9% of total body surface area

      • the area surrounding the genitals (the perineum) epresents 1% of body surface area

  • 1st degree burn (superifical burn) (sunburn)

    • only epidermis is damaged

    • skin is red and swollen

  • 2nd degree burn (partial-thickness burn)

    • epidermis and superficial part of dermis are damaged

    • skin is painful, red, and blistered

    • regrowth of the epithelium can occur

  • 3rd degree burn (full-thickness burn)

    • destroys epidermis and dermis; burned area is painless

    • requires skin grafts, as regeneration is not possible

    • burned area is blanched (gray-white) or black

  • 4th degree burn (full-thickness burn)

    • extends into deeper tissues (nones, muscle, tendons)

    • appears dry and leathery

    • requires surgery and grafting

    • may require amputation

Criteria for deeming burns critical (if any one is met):

  • over 30% of body has second degree burns

  • over 10% of the body has third or fourth degree burns

  • third or fourth degree burns of the face, hands, or feet, or genitals

  • burns affect the airways

  • circumferential (around the body or limb) burns have occured

Skin Cancer

  • most common form of cancer in humans in the US

  • most important risk factor is overexposure to ultraviolet (UV) radiation in sunlight and tanning beds

  • most common types

    • Basal cell carcinoma- least malignant and most common type of skin cancer, arises from cells in stratum basale that are altered so that they can no longer make keratin, lesions appear as shiny, dome-shaped nodules that develop a central ulcer

    • Squamous cell carcinoma- believed to be induced by UV exposure, arises from cells of stratum spinosum, lesions appear as scaly reddened papules that gradually form shallow ulcers, early removal allows a good chance of cure, metastasizes to lymph nodes if not removed

    • Malignant melanoma- most deadly of skin cancers, but accounts for only 5 percent of skin cancers, arises from melanocytes, metastasizes rapidly to lymph and blood vessels, detection uses ABCDE rule for recognizing melanoma

      • A= asymetry (two sides of pigmented mole do not match)

      • B= border irregularity (borders of mole are not smooth)

      • C= color (different colors in pigmented areas)

      • D= diameter (spot is larger than 6mm in diameter)

      • E= evolution (one or more of the ABC characteristics is evolving)

Cancer can be classified two ways

  1. Beneign means the neoplasm (tumor) has not spread

  2. Malignant means the neoplasm has invaded other body areas


Review

  1. There are four types of membranes. What are they? (Know diagrams)

    • Cutaneous (most superficial, skin), serous (visceral and parietal), mucuous (moist), synovial (joints)

  2. Can you list five integument functions?

    • Mechanical damage

    • Chemical damage

    • Thermal damage

    • Ultraviolet radiation

    • Microbes

    • Dessicration

    • Thermoregulation

    • Aids in excretion of urea and uric acid

    • Synthesizes Vitamin D

  3. The layers of the epidermis are (come lets get sun burned):

    • S. Basale

    • S. Spinosum

    • S. Granulosum

    • S. Lucidum

    • S. Corneum

  4. Melanin: cells, layer, color, granules

    • Cells- melanocytes

    • Layer- s. basale of the epidermis

    • Color- yellow to brown to black

    • Granules- melanosomes

    • Influenced by genetics and sunlight

  5. Layers of the dermis:

    • upper papillary

    • reticular papillary

  6. Three pigments contribute to skin color:

    • Melanin

    • Carotene

    • Hemoglobin

  7. List 5 emergency skin colors:

    • Erythema (red)

    • Pallor (white)

    • Jaundice (yellow)

    • Cyanosis (blue)

    • Hematoma (purple)

  8. What are two types of exocrine glands in this system?

    • Sebaceous (oil)

    • Sudoriferous (sweat)

  9. How do the 2 types of sudoriferous glands vary (know location)?

    • Eccrine is cool (everywhere), apocrine smells (at puberty)

  10. Hair:

    • Produced by hair follicle

    • Root is enclosed in the follicle

    • Shaft (part you shave)

    • Keratin (pigment)

    • Melaocytes

    • S. Basale

  11. What are five major regions of the nails?

    • Free edge

    • Body

    • Nail

    • Cuticle

    • Root of nail

    • Growth

  12. Impetigo

    • Bacterial infection; pink, fluid-filled raised lesions around mouth/nose

  13. Contact Dermatitis

    • Itching, redness, and swelling of the skin caused by exposure to chemicals that provoke allergic responses

  14. Basal Cell Carcinoma

    • Skin cancer that arses from cells in stratum basale that are altered so that they can no longer make keratin

  15. Squamous Cell Carcinoma

    • Believed to be induced by UV exposure, this cancer arises from cells of stratum spinosum

Diagrams to Know