1. Integumentary System Skin cc: chexee - https://www.flickr.com/photos/61923475@N00

2. Skin surface area of 1.2-2.2 square meterssurface area of 1.2-2.2 square meters weighs 9-11 lbsweighs 9-11 lbs 7% of total body weight7% of total body weight cc: Chris Nuzzaco - https://www.flickr.com/photos/46925679@N04

3. Functions of Skin 1. 3 types of barriers 2. Chemical, Physical, Biological cc: Yomie - https://www.flickr.com/photos/22743502@N05

4. Chemical 1. skin secretions 2. melanin cc: euthman - https://www.flickr.com/photos/78147607@N00

5. Skin Secretions 1. Acid mantle 2. Sebum 3. Human defensin 4. Cathelicidins cc: † David Gunter - https://www.flickr.com/photos/23812004@N03

6. Melanin 1. Provides a chemical pigment shield to protect from UV damage cc: @Doug88888 - https://www.flickr.com/photos/29468339@N02

7. Physical 1. continuity of skin 2. hardness of the keratinized cells 3. If too thick, lose suppleness and agility 4. If too thin, not as protective 5. Waterproofing glycolipids cc: GrungeTextures - https://www.flickr.com/photos/44718043@N06

8. Physical 1. Lipid soluble items can penetrate 2. oxygen, carbon dioxide, fat-soluble vitamins, steroids 3. certain plant chemicals (poison oak and poison ivy) 4. organic solvents (acetone, dry-cleaning fluid, paint thinner 5. salts of heavy metals (lead and mercury), & drug agents cc: ntr23 - https://www.flickr.com/photos/65919269@N00

9. Biological Barriers 1. Langerhans' Cells 2. active elements of the immune system 3. for immune response to be activated, the antigens must be presented to lymphocytes (WBCs) 4. the Langerhans' cells play this role in the epidermis cc: @Doug88888 - https://www.flickr.com/photos/29468339@N02

10. Biological Barriers 1. Macrophages in the dermis 2. DNA molecules 3. electrons absorb radiation and transfer it to the nuclei, which heat up and vibrate to dissipate heat to surrounding water molecules cc: kevin dooley - https://www.flickr.com/photos/12836528@N00

11. Other Functions cc: vestman - https://www.flickr.com/photos/61417318@N00

12. Body Temperature regulates temperature within homeostatic limitsregulates temperature within homeostatic limits as long as air is cooler than internal temperature, the skin surface loses heat to the cooler objects in its environmentas long as air is cooler than internal temperature, the skin surface loses heat to the cooler objects in its environment cc: Leo Reynolds - https://www.flickr.com/photos/49968232@N00

13. Body Temperature Sweat continuously, just unnoticeableSweat continuously, just unnoticeable when body temp rises, so does sweat productionwhen body temp rises, so does sweat production can lose up to 12L of water per daycan lose up to 12L of water per day evaporation of sweat cools the body to prevent overheatingevaporation of sweat cools the body to prevent overheating cc: joshuaseye - https://www.flickr.com/photos/27279494@N05

14. Body Temperature when the external environment is cold, blood vessels constrict, this causes the warm blood to bypass the skin temporarilywhen the external environment is cold, blood vessels constrict, this causes the warm blood to bypass the skin temporarily this slows passive heat loss, to conserve heat within the bodythis slows passive heat loss, to conserve heat within the body cc: salendron - https://www.flickr.com/photos/8681074@N03

15. Cutaneous Sensation richly supplied with cutaneous sensory receptors (part of the nervous system)richly supplied with cutaneous sensory receptors (part of the nervous system) Meissner's corpusclesMeissner's corpuscles Merkel discsMerkel discs Pacinian corpusclesPacinian corpuscles Hair Follicle ReceptorsHair Follicle Receptors cc: pfarrell95 - https://www.flickr.com/photos/65005341@N03

19. Merkel’s Disc

21. Metabolic Functions When sunlight bombards the skin, modified cholesterol molecules circulating through blood vessels in the dermal layer are converted to a vitamin D precursor These are transported via the blood to other body areas to play various roles in calcium metabolism Calcium cannot be absorbed from the digestive tract without vitamin D

22. Blood Reservoir Can hold large volumes of blood within the dermal layer About 5% of the body’s entire blood volume When other organs need a greater blood supply, the dermal vessels constrict, restricting the blood flow to the skin and shunting it to the needed areas

23. Excretion Limited amounts of nitrogen-containing wastes are eliminated though sweat (although most are excreted through urine) Profuse sweating is an important avenue for water and salt loss