1. The Integumentary System The skin and its accessories

3. General Features zBody’s largest organ zSurface area of 1.2 to 2.2 square meters z4-5 Kilograms (7% of body weight) z1.5-4.0 millimeters thick (paper towel) zDamage impairs nearly every other system

4. Functions zProtection-Provides a chemical, physical(mechanical) and biological barrier zThermoregulation-Body temperature regulation zSensory Organ- temperature, pressure, touch, and pain z Metabolic-Synthesis Vitamin D z Excretion-Small amounts of Nitrogenous wastes, water and salt z Blood reservoir

5. General Structure zEpidermis zDermis zHypodermis /Subcutaneous (not offically considered a part of the skin, but important none the less)

7. Epidermal Layers zStratum corneum- outer most layer; 20- 30 cell layers thick; 3/4 of epidermal layer zStratum Granulosum- 3-5 cell layers; last layer of the epidermis to receive nourishment z Stratum Basale/Germinativum- rapidly dividing cells; melanocytes lie directly above these cells

8. Epidermis Cell Types Keratinocytes Melanocytes zKeratin producing cellsKeratin zConstantly rubbing off zUpper cells are dead zForms an outer protective barrier z Melanin producing cells Melanin z Deepest layer z Protect dividing cells beneath them

9. Keratin Protein found in the epidermis, hair and nails that makes those structures hard and water-repellent.

10. Melanin Dark pigment formed by melanocytes; imparts color to hair and skin

12. Epidermis Thick Skin Thin Skin

13. Dust Mite & Epidermal Cell

14. Features of the Dermis zCell types: fibroblasts, macrophages, WBC’s zFibers: collagen; reticular, elastic z Other Structures: nerve fibers;blood vessels; hair follicles; glands

15. Dermis

16. z“True Skin” zActs like a “body stocking” to hold the body together zConnective tissue; highly vascularized

17. Layers of the Dermis Papillary Reticular PapillaryReticular zLoosely woven zDermal papilla form ridges to make finger- prints zLots of blood vessels z 80% of the dermis z Very dense and collagen rich

18. Hypodermis or Subcutaneous Layer Although not officially considered a part of the skin, it must be examined in order to fully comprehend integumentary structure.

19. Features of the Hypodermis zStorage site for adipose tissue z Loosely anchors the skin to underlying muscle. Sliding allows blows to slide off and allows movement.

20. Factors Determining Skin Color zMelanin: Ranges from yellow to reddish- brown to black. Absorbs radiation from UV light to protect dividing cells beneath it. zHemoglobin: Imparts a pinkish tint; lack of O 2 gives a bluish cast (Cyanosis) z Carotene: Orange to yellow pigment found in many vegetables; accumulates in the stratum corneum

21. Effects of Aging zFewer melanocytes zFewer active hair follicles zDecreases sebaceous gland activity zThin epidermis zReduced sweat gland activity zReduced blood supply zThinner dermis

22. FYI: One Square Inch of Skin Contains z65 Hairs z95-100 sebaceous glands 650 sweat glands z78 sensory apparatuses (for heat) 1,300 nerve ending to record pain z13 sensory apparatuses (for cold) 9, 500, 000 cells z19 yards ( 17 mtrs) of blood vessels 78 yards (70 mtrs) of nerves z19,500 sensory cells at the ends of nerve fibres z160-165 pressure apparatuses for the perception of tactile stimuli.