THE INTEGUMENTARY SYSTEM —Chapter 6

1. THE INTEGUMENTARY SYSTEM—Chapter 6

2. INTRODUCTION – skin & its uses • integumentary system = skin + accessory organs (hair, nails, sweat & oil glands) • skin is a large organ vital to maintaining homeostasis • Skin stats: • Surface area = 1.2 to 2.2 square meters • Weight = 9 to 11 pounds • Accounts for 7% of an adult’s total body weight • 1.5 to 4 mm thick in various parts of the body • Integument = “covering”

4. Functions of Skin: • protection • regulate body temperature • insulation & fat storage • prevents water loss from deeper tissues • houses sensory receptors sensitive to pain, temp., touch, pressure • makes biochemicals such as vitamin D • excretes some waste • blood reservoir – has an extensive vascular supply

5. 2 Layers of Skin: • epidermis = outer layer made of stratified squamous epithelium • dermis = thicker inner layer made of connective & epithelial tissue, smooth muscle, nervous tissue, blood

6. hypodermis = a subcutaneous layer made of loose CT & adipose tissue which binds the skin to the organs under it

7. Epidermal Cells • keratinocytes – make keratin • melanocytes – make melanin • merkel cells – touch receptors • Langerhan’s cells – macrophages

8. EPIDERMIS • 4 layers on most of the body • 5th layer found only in thick skin • epidermis protects underlying tissues against water loss, injury, & the effects of harmful chemicals

9. epidermal cells undergo keratinization as they mature & are pushed toward the surface • top layer of dead cells are eventually shed • 40 pounds in an average lifetime! • totally new epidermis in 25-45 days! • rate of cell division increases where skin is rubbed off regularly forming corns & calluses

10. SKIN COLOR • genetically determined • varies based on the kind & amount of melanin produced, since all people have about the same number of melanocytes

11. influenced by environment (some medications, perfumes, lemons/limes) • influenced by physiological factors (blood color, diet, chemicals such as bilirubin) • 3 pigments affecting skin color = melanin, carotene, hemoglobin

12. DERMIS • Composed of strong, flexible CT • dermis binds the epidermis to underlying tissues • has 2 layers: • papillary • reticular

13. fingerprints result from epidermal ridges projecting inward & dermal papillae projecting upward • increase friction & enhance gripping ability

14. dermal blood vessels supply nutrients to all skin cells & help regulate body temperature (vasoconstriction, vasodilation) • dermis also contains hair follicles, sweat glands, sebaceous (oil) glands, and nerve fibers

15. SUBCUTANEOUS LAYER (Hypodermis) • helps supply the skin with blood • contains adipose tissue which helps conserve body heat & provide cushioning

16. ACCESSORY ORGANS OF THE SKIN 1. Hair • develop in the follicles • new cells push older cells closer to the surface where they become keratinized & die • color genetically determined • an arrector pili muscle attaches to each hair follicle & this pulls the hair erect when stimulated = goose bumps

17. Functions: • sense insects on skin • guard against physical trauma, heat loss, sunlight • eyelashes shield eyes • nose hairs filter large particles from air • eyebrows keep sweat out of eyes • ear hairs keep out bugs

18. 2. Sebaceous Glands • secrete sebum = mix of oil & cellular debris • sebum keeps skin & hair soft, pliable, & waterproof, also acts as a bactericide • start functioning at puberty

19. Sweat Glands (sudoriferous glands) • exocrine glands which consist of a coiled tube • 2.5 million, most in palms, soles, forehead • most respond to elevated body temperature, pain or emotional stress • sweat glands in the armpits & anogenital areas start to function at puberty

20. hyperhidrosis = a condition of profuse, uncontrollable, unpredictable sweating • anhydrosis = lack of sweating

21. 4. Nails • protective coverings for fingers & toes • consists of a nail bed & nail plate • the white moon-shaped lunula at the base of the nail plate is the area where cells are most actively dividing • cells become keratinized & die as they age

22. HEALING OF WOUNDS • scabs = clots + dried tissue • scars result from connective tissue replacing skin

23. Wound healing

24. Homeostatic imbalances of skin: • Skin cancer: • Basal cell carcinoma = least malignant & most common • Squamous cell carcinoma - often on scalp & hands, grows rapidly and metastasizes • Melanoma = cancer of melanocytes, most dangerous type • ABCD rule: • asymmetry, border irregularity, color, diameter

26. Burns • 1st degree = epidermis is damaged • ex. sunburn • 2nd degree = epidermis + part of the dermis are damaged, blisters occur • 3rd degree = epidermis + dermis + hypodermis are all damaged, nerve endings are destroyed • Evaluated by the “rule of nines”

28. Effects of aging: 1) Skin thins 2) Lubricating substances become deficient, so skin gets dry & itchy 3) Elastic fibers clump, skin loses elasticity 4) Subcutaneous fat layer diminishes, often cold • 3 & 4 cause wrinkles 5) Fewer melanocytes & Langerhan’s cells enhance the risk of skin cancer 6) Hair thins due to fewer active hair follicles

29. Consider… • We know the skin plays a role in excreting toxins from our body (namely extra salt) • But, can toxins enter the skin from our external environment? • Why? Why not?

30. Transdermal Patches • Medicated patch that adheres to the skin to deliver medicine. • Medicine goes directly into the bloodstream • Patch allows for controlled release of medication over many hours • Medicine must be small enough to diffuse through the skin

31. Clear backing Drug reservoir Contact adhesive Patch Epidermis Dermis Blood Vessel

32. Popular uses • Nicotine patches • Alzheimer’s • Estrogen/testosterone • Motion sickness