Chapter Four

Skin and Body Membranes

Classification of Membranes

• Epithelial– Cutaneous

• Skin• Stratified squamous

– Mucous (mucosa)• Lines cavities• Simple columnar

• Serous– One layer– Simple squamous– Serous fluid

• Parietal & Visceral– Lines body cavities– Around organs– Pleura & Pericardium– Simple squamous

Functions of the Skin

• Protection– Against disease– Insulates & cushions– UV protection– Chemical protection

• Defense– 1st line of defense

• Prevention of Dehydration– Keratin– Keeps H2O in & out

Functions of the Skin

• Maintenance of Body Temp.– Heat loss – sweat– Heat retention – blood flow

• Excretion of Wastes– Salts– Urea– H2O

• Reception of Stimuli– Touch, pressure, pain, cold, heat

• Vitamin D Synthesis– Cholesterol molecules Vitamin D (sunlight)

Layers of the Skin - integumentary

• Epidermis– Strata

• Stratum basale– Closest to dermis– Undergoes mitosis– Nutrients from diffusion

• Stratum spinosum– Flattened cells w/ spines

• Stratum granulosum– Granules w/ keratin

• Stratum corneum– “horny”– 20-30 cell layers– Soles. Palms, fingertips-stratum lucidum

Cell Types

• Keratinocytes–Make keratin

• Melanocytes–Make melanin– Secretes melanin – basale layer

• Langerhans cell–Macrophages-eat foreign substances

Skin Color – amount and kind

• Pigments– Melanin

• Reddish brown, or black– Carotenes

• yellow– Hemoglobin

• rosy

• Emotional– Redness (sympathetic)

• Embarrassment • Anger• Fear• Allergies

Dermis – “hide” leather

• Thick connective tissue layer beneath stratum basale.– Collagen– Elastin

• Papillary layer– Upper, uneven– Receptors (pain, touch)– Dermal papillae

• Fingers-fingerprints• Soles-footprints

Dermis cont…

• Reticular layer– Deepest– Blood vessels– Sweat and oil glands– Blood supply when restricted• Degeneration• Ulceration – bed sore

Appendages of the Skin• Glands– Sebaceous glands

• Oil• Sebum: lubricant, bacteria killing• Whiteheads (blocked oil gland) blackhead acne• Seborrhea – excess oil

– Sweat glands – 500 ml a day (25 million)• Eccrine

– Sweat– Clear– 99% water– Salts, urea, lactic acid,– pH 4-6

• Apocrine– Axillary & genital areas– Fatty acids, proteins, sweat (yellowish)– Empty into hair follicles

Appendages of the Skin cont..

• Nails– Modified epidermal cells– Keratin

• Hair– 100,000 hairs scalp– Follicle

• Keratinized cells• Arrector Pili (goose bumps)– smooth muscles -Hairs

erect-increase blood flow to skin

– Cuticle• Keep hairs separate

Infections and Allergies1000 different conditions

• Fungi– Athletes foot fungus– Ringworm

• Bacterial– Boils and carbuncles

• Staphylococcus into hair follicles• Oil glands

– Impetigo• Viruses– Herpes “cold sores”– Warts

• Allergies– Eczema– Contact dermatitis– “rash”

• Unknown– Eczema– Psoriasis– Hives

• Yeasts

Skin in Stress• Wound Repair– Wound– Inflammatory reaction

• Blood flow– Edema

• swelling– Clots

• Stop bleeding– WBC’s

• Fight bacteria– Pus

• Dead blood cells• Dead bacteria

– Scabs

Skin in Stress cont…• Burns– Thermal

• Heat• Chemical – electrical - UV

– First degree• Epidermis “red”• Heal 2-3 days

– Second degree• Epidermis & dermis• Blisters

– Third degree• Skin blackens• Skin grafts

– Risk of death• Fluid loss , imbalance of electrolytes• Kidney failure• Replace proteins , infection

Skin Cancer• Basal Cell Carcinoma

– Most common– Alters stratum basale cells

• Uncontrolled mitosis can’t form keratin

• Squamous Cell Carcinoma– Stratum spinosum– Scaly reddish papulae– Spreads to lymph nodes

• Malignant Melanoma – (5%)– Brown black patches– Lymph & blood vessels– ABCD rule moles– Asymmetrical, border, color, diameter 76mm

Disease States• Erythema

– Turns red• Pallor, blanching

– Anemia– Low blood pressure

• Jaundice– Yellowing– Liver disorder

• Porphyria– purple

• Bruises– Hematoma– Broken capillaries

• Cyanosis– “bluish”– Low 02 in blood