Skin and the Integumentary System

Chapter 6

Functions of the Skin

Maintain homeostasis Protective covering Contains immune cells Synthesizes vitamin D Excretes wastes Slows water loss Regulates body temp Houses sensory receptors

Layers of Skin 3 layers:

Epidermis ▪ Outer layer

Dermis ▪ Inner layer

Subcutaneous ▪ Hypodermis layer

Cut-, skinDerm-, skinEpi-, uponHypo-, below

Epidermis Thickest on palms and

soles 0.8-1.4mm

Accessory structures Hair follicles Nails

Melanocytes Provide melanin

Epidermis Composed of stratified squamous epithelium Keratinized

Cells synthesize keratin packed cells Separated from dermis by basement membrane Lacks blood supply

Layers of Epidermis Stratum corneum

corneum = horn (Latin) Outer keratinized layer,

dead Desquamation

Stratum lucidum lucid = clear (Latin) Palms, soles

Stratum granulosum granulose = granular

(Latin) Flat, granular (keratohyalin)

Layers of Epidermis

Stratum spinosum Spiny, prickly Dividing, melanocyte branches

Stratum basale (germinativum) Basal = basement, bottom layer Melanocytes, dividing, deepest layer

Dermis Bind epidermis to underlying

tissue Irregular dense CT Muscle fibers

Smooth & skeletal Dermal papillae

Increased surface area to nourish epidermis

Fingerprints Friction for gripping

Average thickness 1.0-2.0mm

Dermis Accessory structures

Nerve cell processes▪ Pacinian (heavy

touch/pressure)▪ Meissner’s (light

touch/pressure)▪ Free nerve endings

(temperature, pain) Blood vessels Sweat glands

Subcutaneous Layer “Hypodermis” Loose CT & adipose

tissue Major blood vessels Insulation

Hair Follicles From epidermal cells Extends into dermis

Contains hair root Hair color

Melanin production▪ Albinism

Arrector pili muscle Smooth muscle Attaches to each

follicle▪ Autonomic innervation

Hair Growth Cyclic growth

Formed by cells in follicle

Keratinize and die Form hair shaft

Type of hair Eyelash

▪ Grow 30 days, 100 days rest

Scalp▪ Grow 3-6 years, rest few

months▪ 0.3 mm/day

Sebaceous Glands Associate with hair

follicles Absent on palms and

soles Holocrine glands

Release entire cells Secrete sebum

Mixture of fatty acids and cellular debris

Secreted into hair follicle

Excess sebum acne

Seb-, grease

Clinical Application Acne

Disorder of sebaceous glands

Hormonally influenced At puberty Adrenals androgens Stimulates sebum

production

Clogged gland Excess sebum, epithelial

cells Blackheads & whiteheads Good environment for

anaerobic bacteria

Clinical Application Immune system triggers inflammation

Pimple Treatment options

Antibiotics Estrogen Retinoic acid (Vitamin A derivatives)

▪ Accutane

Nails Protective coverings on fingers,

toes Made of:

Nail plate Nail bed (skin) Lunula

▪ White region▪ Half-moon shape▪ Active in growth

Reflection of health status Blue = cyanosis; white = anemia;

pigment = injury or melanoma; depressions/furrows = anemia, malnourishment; red streaks = ulcers, hypertension, RA

Growth rate 0.5-1.2 mm/day

Sweat Glands Sudoriferous glands

Widespread in skin▪ Deep dermis or

subcutaneous layer Eccrine glands

Most numerous Apocrine glands

Active in puberty Modified sweat

glands Ceruminous Mammary

Sweat Glands Eccrine glands

Most numerous Response to

▪ High temp▪ Exercise▪ Stress (on hands)

Open as pore▪ Forehead, neck, back

Sweat Glands Apocrine glands

Onset @ puberty Response to

▪ Fear▪ Pain▪ Distress

Open into hair follicle▪ Armpit▪ Groin

Odor▪ Bacterial metabolism

of secretions

Sym

path

etic

resp

onse

Sweat

Water Salts

Sodium Chloride Potassium Magnesium

Wastes Urea Lactate

Regulation of Body Temp Heat

Product of cellular metabolism

Active cells are major heat producers Skeletal muscle

As body temp , body releases heat

Homeostasis Maintain body temp at

37C or 98.6 F

Releasing Body Heat Radiation (2)*

Most of heat loss Infrared heat rays escape from

warmer to cooler surroundings Evaporation (5)*

At high temp, eccrine sweat glands release sweat onto skin

Heat carried away as skin cools Conduction

Heat transferred from body directly to cooler object

Ex. Cold car seats Convection (4)

Warm air circulates away from body

Conserving Body Heat Dermal blood

vessels Reduce heat-carrying

blood thru skin Muscle activity

Increased cell respiration ▪ Heat production

Shivering▪ Small groups of

muscles contract▪ Produce heat

Problems in Body Temp Regulation Hyperthermia

Abnormally high Humid air prevents

evaporation of sweat▪ No cooling

High air temp reduces radiation cooling

Hypothermia Abnormally low Shivering mental

confusion, lethargy, loss of reflexes, shut down of major organs▪ Some surgeries

(heart, brain) require body to be cooled less oxygen is required

Skin Color

Genetic Factors Melanocytes

▪ Same # in all people Melanin production

▪ Varies by person Melanin production

▪ High darker skin▪ Low fairer skin

Albinism▪ No melanin

Environmental factors Darken existing

melanin Stimulate

production▪ Sunlight▪ UV light from

▪ Sunlamps▪ X rays

Tans fade▪ Pigmented epidermal

cells keratinize ▪ Wear away

Skin Color Physiological Factors

Blood vessels in dermis adds color▪ Content of vessels

▪ High oxygen hemoglobin is bright red Pinkish hue to skin

▪ Low oxygen hemoglobin is dark red Bluish hue to skin (cyanosis)

▪ State of vessels▪ Dilation skin reddens▪ Constriction skin pales

Dietary influences Carotene yellow/orange skin tone

Health influences Jaundice yellowish skin (liver)

Healing of Wounds and Burns Inflammation

Response to injury or stress Healing events depend on nature of

injury Cuts

Shallow ▪ Epithelial cells divide fill in gap

Deep cut ▪ Blood vessels break blood clot

Healing of Wounds and Burns Clot

Scab formation▪ Fibrin, blood cells,

platelets, fluids Fibroblasts

Secrete collagen ▪ Binds wound together

Scar Extensive wound Connective tissue

on skin surface

Burns First degree

Superficial partial thickness▪ Injuring epidermis only▪ Healing in 2-3 days

Common examples▪ Sunburn▪ Scalding water▪ Chemicals

Treatment▪ Flush with cool water (no ice)▪ Aloe (no oil)▪ Clean, dry bandage

Burns Second degree

Deep partial thickness▪ Injures epidermis and dermis▪ Fluid escapes capillaries blisters▪ Healing time 1-2 weeks

Common examples▪ Prolonged sunburn or scalding water▪ Brief exposure to flame

Treatment▪ Flush with water, bandage▪ Do NOT break blisters▪ > 2-3 inches, see physician

▪ Hydration▪ Antibiotics▪ Grafting

Burns Third degree

Full-thickness▪ Epidermis, dermis, accessory

organs▪ Healing time: weeks to months

Common examples▪ Contact with flame▪ Corrosive chemicals▪ Immersion in hot liquids

Treatment▪ Burn center▪ Debridement▪ Grafting

Grafting Autograft

“Auto” self▪ Remove skin from unburned part of body and “transplant” it to

injured site Homograft

“Homo” like▪ Cadaveric skin used if can’t do autograft

Skin substitutes Amniotic membrane Artificial membrane Cultured epithelial cells

Scarring

Healing of Burns

Treatment of patient: Requires estimate

of body surface injury▪ Replace body fluids

and electrolytes▪ Determine amount of

skin needed for graft Use “rule of nines”

▪ Divide skin surface into regions

▪ Each region = 9% (or multiple of 9%)

Life Span ChangesAging skin shows many signs…

Cell cycle slows Age (liver) spots Dermis reduced

Connective tissue growth slows ▪ Slower wound healing

Loss of fat▪ Wrinkles & sagging skin

Melanin production slows Hair grays/whites

Less vitamin D production Needed for calcium uptake in bones

Life Span ChangesAging skin shows many signs…

Hair growth slow Thins and # follicles decreases

Lowered blood supply to nail beds Dulls/hardens nails

Sensory receptors decline Less sensitive to pain/pressure

Inability to control body temperature # sweat glands drop & dermis blood vessel

numbers

Common Skin Disorders Athlete’s foot

Skin fungus infection (Tinea pedis)

Boil Bacterial infection, bacteria enter

skin via follicle

Chickenpox Varicella-zoster infection; blistery

lesions that scab

Common Skin Disorders Eczema

Dry, itchy, scaly skin (genetic)

Mole Benign skin tumor (nevus) usually pigmented brown

black

Psoriasis Red skin w/ silvery scale

Rashes Infectious

Roseola Measles Rubella 5th disease Shingles Impetigo Lyme disease RMSF Meningitis Candidiasis

Allergic Hives Penicillin Food allergies Poison ivy Cosmetics

Autoimmune Lupus Psoriasis

Skin CancerTypes Basal cell carcinoma

Most common Basal layer of epidermis Nodule, shiny bump, scar-like lesion

Squamous cell carcinoma 2nd most common Upper layers of skin (squamous) Begin as scaly red patches, open sores,

elevated with centralized depression Typically superficial

Skin CancerTypes Malignant melanoma

Most deadly Brown/black patches, nodules Look like or arise from moles

Skin CancerRisks

Fair skin, hair, eye color Family history Personal history Chronic sun exposure History of sunburns early in life Certain types of moles, # moles Freckles

Sun sensitivity, sun damage

Skin CancerDetection A

Asymmetry B

Border irregularity (scalloped, notched)

C Color variation

D Diameter > ¼ inch

E Evolution

Skin CancerTreatment

Excision Virtually all types of skin cancer are

100% curable if caught early Invasive

Lymph node testing Chemotherapy Immunotherapy

Suggested Homework Problems Chapter assessments

3-6, 9, 11-14, 17, 19-25, 27, 28 Integrative Assessments/Critical

Thinking 1-7