INTEGUMENTARY SYSTEM

The skin is the largest organ.

Skin Functions• Physical barrier

• General senses: touch, pressure, pain, temperature

• Vitamin D source

• Temperature regulation

• Excretion of wastes

Types of cells: • Keratinocytes

– produce keratin

– totally replaces epidermis every 25-45 days

• Melanocytes– produce melanin

• Langerhans– dermal macrophages

• Merkel cells– sensory receptors for touch

Skin Layers

• Epidermis - Stratified squamous epithelium that is keratinized

• Dermis - Irregular dense fibrous connective tissue

Major Layers of Skin

• Epidermis

– stratum corneum

• outermost

• thickest

• dead, flaky, dandruff

– stratum lucidum

• (clear)

– stratum granulosum

• increased keratinization

Major Layers of Skin

• Epidermis

–stratum spinosum• (prickly layer)

–stratum basale • (stratum

germinativum)

• mitotic division

• Contains melanocytes

Skin Layers

• Dermis

– Papillary layer contains:

• Dermal papillae

• Meissner’s corpuscles (touch receptors)

– Reticular layer

• Arteries

• Veins

• Glands

• Pacinian corpuscles (pressure receptors)

Skin Color• Melanin

– Yellowish to reddish-brown to black

– Racial differences result from kind and amount of melanin

– Freckles: local accumulation of melanin

– Melanin increase due to damage from ultraviolet radiation

• Excessive exposure to sun damages elastin fibers, depresses immune system, and alters DNA possibly leading to skin cancer

• Carotene

– Yellowish, orange

– Accumulation due to diet

• Hemoglobin - reddish

Color variations

– Redness (Erythema)• blushing, fever, inflammation, allergy

– Pallor• fear, anger, stress, anemia

– Jaundice• yellowish color due to bile; liver disorder

– Bronzing• Addison’s disease ; adrenal cortex disorder

– Bruises (hematoma)• clotted blood beneath skin

Accessory Structures

• Sudoriferous (Sweat) Glands–Eccrine glands

•covers most of body; especially hands, feet, and head

•Eccrine secretion contains water, salts, vitamin C, antibodies, waste (urea, uric acid, ammonia), and lactic acid

Accessory Structures

• Sudoriferous (Sweat) Glands–Apocrine glands (axial and genital

areas)• Apocrine secretions add fatty substances and proteins

• Breakdown of aprocrine secretions by bacteria causes body odor

• Begin functioning at puberty

Accessory Structures

• Specialized Sudoriferous (Sweat) Glands–Ceruminous glands

- secrete wax

–Mammary glands - secrete milk instead of sweat

• Sebaceous (Oil) Glands

– Secrete sebum

• softens and lubricates skin and hair

• waterproofs

• activated by hormones during puberty

– Whitehead - gland blocked by accumulated sebum

– Blackhead - dried, oxidized sebum

– Acne - active inflammation of sebaceous glands

– Seborrhea (Cradle cap) - overactive sebaceous glands

Hair & Hair Follicles

– Structure of hair• Shaft - projects from

skin

• Root - embedded in skin

• 3 layers of ketatinized cells

– medulla - core– cortex - surrounds core– cuticle - outermost

layer

Hair & Hair Follicles

– Structure of follicle

• Hair bulb - expanded end of follicle

• Hair papilla - dermal papilla protruding into hair bulb; supplies nutrients; stimulates growth

• Hair matrix - produces hair; active division; older cells pushed to top, increase keratinization & die

• Arrector pili -muscle that raises hairs; causes goose bumps

Distribution, Types, & Growth of Hair

• Vellus - fine body hair of children and females• Terminal - coarse hair of scalp and eyebrows• Growth stimulated by androgens• Affected by nutrition• Average growth rate = 2mm per week• Hair Cycles vary

– scalp follicles active approx. 4 yrs– eyebrow follicles active 3-4 months

Hair Thinning & Baldness

–After 40’s resting cycles lengthen

–Hair not replaced as fast as lost

–Baldness = alopecia

• Male Pattern Baldness

–Genetically determined

–Sex influenced

Nails• Scale-like modifications of epidermis

• Structure

– Free Edge

– Body

– Root

– Nail Bed - epidermis beneath nail body

– Nail Matrix - proximal portion of nail bed

– Lunula– Nail folds

– Eponychium (cuticle)

Skin Disorders• Warts - nonmalignant epithelial growth caused by a

virus

• Cold sores (fever blisters)

– small fluid-filled blisters around lips & mouth

– caused by a herpes simplex virus

• Acne - inflammation of sebaceous glands

• Impetigo - inflamed lesions caused by staphylococcus infection

• Decubitus ulcers (bed sores) caused by irritation and inadequate circulation

Skin cancers• Most skin tumors benign (ex. Warts)

• Basal Cell Carcinoma– least malignant

– approx. 30% of caucasians will develop this

– 99% cure rate

• Squamous Cell Carcinoma

– Scaly elevation arising from the stratum spinosum

Cutaneous melanoma• Arise from melanocytes• 2 types

– melanocarcinoma– malignant melanoma

• Irregular growths with variety of pigmentation (brown, gray, black, or blue)

• Occur in all age groups, usually in people who sunburn easily

• More common in people who get short intense exposure to sunlight.

• Survival rate is low.• May begin in regular skin or mole

ABCDE rule

–A - Asymmetry

–B - Border irregularity

–C - Color

–D - Diameter

–E - Elevation

ABCD’s of Skin Cancer

Classification of Burns

• First-degree burns - involves only epidermis

• Second-degree burns - involves both epidermis and dermis

• Third-degree burns - complete destruction of both layers, probable involvement of subcutaneous tissue

• Burns also classified by the extent of burn area

Classification of Burns• RULE of NINES• Head = 9%• Anterior Thoracic = 9%• Posterior Thoracic = 9%• Anterior Abdomen = 9%• Posterior Abdomen = 9% • Left Arm = 9%• Right Arm = 9%• Anterior Left Leg = 9%• Posterior Left Leg = 9%• Anterior Right Leg = 9%• Posterior Right Leg = 9%• Genitals = 1%