2. How do I keep my body healthy?

4.  Components: cutaneous membrane integument › Skin (aka cutaneous membrane or integument) › Hair › Nails

5.  Components: cutaneous membrane integument › Skin (aka cutaneous membrane or integument) › Hair › Nails Fun fact: The skin is the largest organ in the body. The skin of an average adult weighs more than 9 lbs!

6. Functions 1. Protection 2. Thermoregulation 3. Excretion of wastes 4. Synthesis of vitamin D

7. 1. Protection › From mechanical and chemical damage  Barrier of tough, keratinized cells  Pain receptors warn body of possible damage › From pathogens  Unbroken surface  Acidic secretions inhibit bacterial growth  Phagocytes ingest foreign material › From UV radiation  Melanin absorbs UV light and prevents it from reaching deeper layers

8. 1. Protection › From thermal damage  Pain receptors warn body of possible damage › From desiccation (drying out)  Keratin and other substances keep skin fairly waterproof

9. 2. Thermoregulation How does the skin help us cool down? How does the skin help us warm up?

10. 2. Thermoregulation How does the skin help us cool down? › Evaporative cooling (sweating) › Increased blood flow through skin (increases heat loss) How does the skin help us warm up? arrector pili › Goose bumps: arrector pili muscles contract to pull hair upright, and add insulation to body › Decreased blood flow through skin (reduces heat loss)

11. 3. Excretion of wastes – › The sweat glands excrete metabolic wastes (urea, uric acid), salt, and lactic acid (in addition to water) 4. Synthesis of vitamin D › When UV light hits the skin, modified cholesterol molecules are converted into vitamin D.

12. Turn & Talk (5 min), then share with class. Scholar on left …  Name the four major functions of the integumentary system.  Explain how the skin fights pathogens. Scholar on the right …  Name the three components of the integumentary system.  Explain how the skin allows us to thermoregulate.

13. The skin is composed of two layers: 1) Epidermis – made of _______________ tissue 2) Dermis- made of _______________ tissue

14. The skin is composed of two layers: 1) Epidermis – made of epithelial tissue 2) Dermis- made of dense connective tissue

15. Fun fact: Blisters occur when friction causes the epidermis to pull away from the dermis.

16. Epidermis is made of epithelial tissue. Quick Review: What are the characteristics of epithelial tissue?

17. Epidermis is made of epithelial tissue. Quick Review: What are the characteristics of epithelial tissue?  Form continuous sheets, have cell junctions  Avascular  Apical side free  Other side attached to basement membrane  Regeneration Remembering these characteristics will help you understand the structure and function of the epidermis!

18. The epidermis has multiple strata or layers. Only the deepest layer contains actively dividing cells and melanocytes. Why? Because the deepest layer is closest to the blood supply. As new cells form, older cells are pushed towards the surface

19. As the cells are pushed away from the blood supply, they atrophy and flatten. The most superficial layer is made of the dry, keratinized membranes of skin cells.

20. Two main cell types in epidermis: 1) Keratinocytes › Keratin-producing cells › Keratin is the protein that makes skin tough and waterproof. › Most abundant cell in epidermis 2) Melanocytes › Melanin-producing cells › Melanin is the brown-black pigment that is largely responsible for skin, hair, and eye color › Melanin absorbs UV light to product DNA from damage › Found only in deepest layer of epidermis

21.  Major determinants of skin color › Amount / type melanin › Amount carotene (from fruits and veggies) › Amount oxygen in blood  Adaptive significance › Trade off between UV protection and vitamin D production

22. The dermis is made of what tissue?

23. The dermis is made of what tissue? Connective (specifically, dense irregular) Connective tissue cushions and binds things together. In the skin, the connective tissue holds together lots of different elements: Exocrine glands Hair follicles Nerves and sense receptors Blood vessels The collagen and elastic fibers of the dermis give skin its strength and elasticity

24. First degree burn: only epidermis is damaged. Second degree burn: Damage extends partway into dermis. Third degree burn: Damage extends all the way through dermis.

25. First degree burn: only epidermis is damaged. Second degree burn: Damage extends partway into dermis. Third degree burn: Damage extends all the way through dermis. Signs: red, swollen skin Example: most sun burns Will heal on own

26. First degree burn: only epidermis is damaged. Second degree burn: Damage extends partway into dermis. Third degree burn: Damage extends all the way through dermis. Signs: red, swollen skin Example: most sun burns Will heal on own Signs: blistering Skin will heal with care

27. First degree burn: only epidermis is damaged. Second degree burn: Damage extends partway into dermis. Third degree burn: Damage extends all the way through dermis. Signs: red, swollen skin Example: most sun burns Will heal on own Signs: blistering Skin will heal with care Signs: blackened or blanched (gray-white) skin, lack of pain due to damaged nerves Skin will not heal; grafts must be done

28. Burned skin can no longer carry out its functions Turn & Talk Quick review: What are the functions of the skin? Analyze: Which functions are most critical? 1)Protection from abrasion / chemical damage / UV damage / pathogens / against dessication 2)Excretion of wastes 3)Thermoregulation 4)Synthesis of Vitamin D

29. Burned skin can no longer carry out its functions Most critically, skin can no longer › Prevent loss of fluids and electrolytes  Fluid loss and electrolyte imbalance can cause kidneys to shut down and patients to go into shock due to low blood volume.  Happens almost immediately, unless fluids are replaced. › Protect the body from pathogens  Infection becomes a major concern within 2-3 days following severe burns.

30.  Burned skin cannot thermoregulate. Hypothermia becomes a problem.  3 rd degree burns cannot regenerate. Scar tissue forms. Scar tissue does a poor job of perfoming the functions of skin, and if the scar tissue is extensive, mobility may be affected.

31. In a short paragraph explain how burn classification and severity is related to the structure and function of the skin.