1. The Integumentary System Chapter 5

2. Cool Skin Facts: 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. Two Regions Epidermis • Composed of epithelial tissue • Outermost layer • Non-vascular • Keratinized stratified squamous epithelium • Composed of fibrous connective tissue • Underlying layer • vascularized Dermis

4. Cells of the epidermis • 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. Layers of Epidermis • 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. Epidermis layers cont. • 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

7. Dermis Papillary and Reticular Layers

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

9. Reticular Layer • 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. Skin Pigments • 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. Skin color signs of diseases • 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. Skin diseases continued…. • Bronzing-Addison’s disease, hypofunction of adrenal cortex • Black and blue marks- hematomas (bruise)

13. Appendages of the skin • 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. Sebaceous Oil glands • Found everywhere except palms, soles of feet • Holocrine gland • Sebum- oily • Soften and lubricates hair • Bactericidal action • Seborrhea – “cradle cap”

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

16. Hairs and Hair Follicles • Sense insects before they sting • Head hair protects against UV, heat loss, physical trauma • Eye lashes- shield eyes • Nose hairs- filter large particles like lint and insects

17. Structure of Hair • Pili-”hairs” consist of largely dead, keratinized cells. • Hard keratin-tough and durable, individual cells do not flake off • Soft Keratin- found in typical epidermal cells

18. 3 Concentric Layers of the Hair • Medulla- core, large cells and air spaces, not found in fine hairs • Cortex- bulky layer surrounding medulla, several layers of flattened cells • Cuticle-single layer of cells, overlaps on another like shingles • *Red heads have trichosiderin- iron-containing pigment

19. Hair Follicle Structure

20. Types of Hair • Vellus • Pale, fine • Females and children • Terminal • Coarser • Scalp and eyebrows • Androgen stimulates

21. Hair Growth Facts • Hirsutism- excessive hairiness, caused by excessive androgens • 2.5 mm/week • Lose about 90 hairs/day • Growth cycle • Active (anagen) • Regressive ( catagen) • Resting phase (telogen)

22. Hair thinning and Baldness • Alopecia- hair thinning or baldness • Drug induced • Excessive vitamin A • Chemotherapy • Burns • Radiation • Alopecia areata- autoimmune • Male Pattern Baldness • Minoxidil treatment

23. Functions of the Integumentary System • Protection • Chemical, physical, and biological barriers • Body Temperature Regulation • Cutaneous Sensation • Metabolic Functions • Blood Reservoir • Excretion

24. Additional Facts . . . • Low pH retards bacterial growth (acid mantle) • Natural antibiotic (human defensin) • Cathelicidins – fights strep bacteria • Some substances can penetrate skin, ie. Lipid-soluble substances (oxygen, Carbon dioxide, vitamins A,E,D,K), oleoresins (poison ivy)

25. More . . . • Organic solvents (ie. Acetone, paint thinner, etc.) • Salts of heavy metals (lead, mercury, nickel) • May lose 12 L of body fluid per day • Can transform cortisone into hydrocortisone • 5% of blood volume in skin • Lose water and salt through skin

26. Homeostatic Imbalances • Skin Cancer- benign and malignant, p53 gene (tumor suppressor gene) • Types of Skin cancer: • 1)Basal Cell carcinoma • 2)Squamous cell carcinoma-arises from keratinocytes in stratum spinosum • 3)Melanoma- cancer of melanocytes

27. Skin cancer checklist • A rule : asymmetry • B rule : border irregularity • C rule: color • D rule: diameter • E rule : elevation

28. Burns • First degree: epidermis only damaged, redness, swelling, pain, heals in 2-3 days • Second degree: epidermis and upper region of dermis, blisters, 3-4 weeks no scarring • Third degree: all layers, appears gray-white, cherry red, or blackened, not painful because nerve endings, skin grafing

29. Other interesting facts: • Lanugo coat- 5-6 month fetus, delicate coat of hairs • Vernixcaseosa- cheesy substance on newborns