2. Surface Area = 1.2-2.2 sq.m(1/2 white board) Weight = 4-5 kg (8-9lbs) 7% of body weight Thickness – 1.5-4.0 mm Millions rub off each day- New epidermis every 25-45 days

3. Epidermis Dermis  Composed of epithelial tissue  Outermost layer  Non-vascular  Keratinized stratified squamous epithelium  Composed of fibrous connective tissue  Underlying layer  vascularized

4.  Keratinocytes- produce keratin, tightly connected by desmosomes, continuous mitosis  Melanocytes-pigment called melanin(protects from UV), spider-shaped cells, found in deepest layer of epidermis  Merkel cells-shaped like spikey hemisphere, Merkel disc has sensory function  Langerhans cells -made on bone marrow, macrophages

5.  Stratum Basale- ( Basal Layer) bottom, attached to dermis, youngest keratinocytes, 10-25% are melanocytes  Stratum Spinosum (Prickly Layer) intermediate filaments resist tension attach to desmosomes, keratinocytes appear spiny  Stratum Granulosum (Grandular layer) 3-5 layers thick, keratinocytes flatten, accumulate keratohyaline and lamellated granules

6.  Stratum Lucidum (clear layer)- thin, translucent, dead keratinocytes  Stratum Corneum (Horny Layer)- 20-30 layers thick, ¾ of epidermal thickness, 40 lbs shed in lifetime

8.  Thin, blood vessel rich, areolar connective, collagen and elastin fibers, loosely woven  Dermal papillae- indent overlying epidermis, touch receptors(Meissner’s corpuscles), fingerprints

9.  80% of thickness of dermal layer  Dense irregular connective tissue  Extra cellular matrix contains thick bundles of interlacing collagen fibers, form cleavage, tension and lines in the skin, flexure lines (at joints)

10.  Melanin- › Protects from UV › All have same number only make different amounts  Carotene- › Yellow to orange › Accumulates in fatty tissue and stratum corneum (soles of feet and palms) › *Hemoglobin (found in Red blood cells) can give reddish hue

11.  Redness (erythema)- embarrassment, fever, hypertension, inflammation, allergy  Pallor (pale)- fear, anger, stress, anemia, low blood pressure  Jaundice (yellow)- liver disorder, bile pigments accumulate in body tissues, bilirubin secreted by liver cells as component of bile

12.  Bronzing-Addison’s disease, hypofunction of adrenal cortex  Black and blue marks- hematomas (bruise)

13.  Nails  Sweat glands (sudiferous glands) pH 4-6 › Eccrine (merocrine)-palms, soles of feet, forehead › Apocrine gland- hair follicles, body odor, musky, unknown function › Other- ceruminous glands (ear wax) › Mammary glands- milk  Sebaceous glands (oil)  Hair

14.  Found everywhere except palms, soles of feet  Holocrine gland  Sebum- oily  Soften and lubricates hair  Bactericidal action  Seborrhea – “cradle cap”

15.  Hard Keratin  http://www.thaimedicalnews.com/wp- content/uploads/healthy-finger-nails- diagram.gif