1. Copyright © 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 1

2. Copyright © 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 2  Called a membrane because it covers the body  Called an organ because it contains several kinds of tissues  Called a system because it has organs and other parts that work together for a particular function

3. Copyright © 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 3

4. Copyright © 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 4  Epidermis—outermost layer  Dermis—“true skin”  Subcutaneous fascia or hypodermis— the innermost layer

5. Copyright © 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 5  Epidermis (cuticle)  Outermost layer of the skin  Composed of a surface of dead cells with an underlying layer of living cells  Contains sebaceous and sudoriferous glands as well as hair follicles  Melanocytes (produces melanin) are located in the epidermis Melanin: pigment that gives skin its color

6. Copyright © 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 6  Dermis (corium)  Called the “true” skin  Contains the blood vessels and nerves Each inch of skin contains many blood vessels  Subcutaneous  Innermost layer  Contains adipose, which cushions and insulates the body’s organs

7. Copyright © 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 7  Skin has hair in all areas except the soles of the feet and palms of the hands  Hair blocks foreign particles from entering the body through structures such as the nose and eyes  The visible portion is called the shaft  The hair follicle is the root with its covering  Hair- external insulation

8. Copyright © 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 8  Three types of glands in the skin:  Sebaceous glands (oil) Located everywhere except palms of hands and soles of feet Sebum (oil) causes the skin to be soft and waterproof Coat the hair with oil  Sudoriferous glands (sweat) Help regulate the body temperature and excrete body wastes cool the body

9. Copyright © 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 9  Ceruminous glands Located in the auditory canal of the ear Secrete wax that helps protect the ear from infection and prevents entry of foreign bodies

10. Copyright © 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 10  Function is to protect fingers and toes from injury- protective covering  Formed from dead, keratinized epidermal cells  Root is covered by skin at the area of attachment to finger or toe  Lunula is the crescent-shaped white area near the root

11. Copyright © 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 11  Dermatology  Study of skin  Dermatitis is inflammation of the skin  Skin lesions can be seen with visual inspection Size, shape, texture, and color often reveal cause Biopsy is used to identify the causative organism  Fingerprints and toe prints are unique to each person

12. Copyright © 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 12  Acne  Caused by increased secretion of oil related to increased hormones during puberty Primarily affects the face, chest, and back  Digests sebum  Attracts neutrophils  Neutrophil digestive enzymes cause lesions, “pus pockets”  Oil-based cosmetics worsen disease

13. Copyright © 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 13  Benzoyl peroxide dries plugged follicles, kills microbes  Tetracycline (antibiotic)  Accutane – inhibits sebum formation

14. Copyright © 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 14  Albinism  Inherited disorder in which melanin is not produced  Alopecia  Baldness  Athlete’s foot  Contagious fungal infection of the foot

15. Copyright © 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 15  Dandruff  White flakes of dead skin cells from the scalp  Eczema  Group of disorders caused by allergic or irritant reactions  Psoriasis  Chronic skin disorder in which too many epidermal cells are produced  Rashes  May result from viral infection, especially in children

16. Copyright © 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 16  Skin cancer Sun and skin cancer Damage by ultraviolet rays Types of skin cancer Three forms are basal, squamous, and melanoma  Skin lesions  Differ in texture, color, location, and rate of growth

17. Copyright © 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 17  Skin and hair care  Skin care products include soap, astringents, and cosmetics  Ways to remove hair include wax, depilatory creams, and electrolysis Tattooing (permanent makeup) Risk of infections, allergic reaction, and complications during MRI

18. Copyright © 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 18  House dust is mainly skin flakes!  If you laid out all your skin on a flat surface, it would have an area of about 2 square meters.  Skin weighs about 2.5 kilograms - the largest organ in the body.  What hurts if you pull it, but doesn't hurt if you cut it? Your hair, of course!  Skin is elastic - it springs back into shape when stretched. Some medicines (estrogen, nicotine) can pass through the skin, but others cannot (insulin). Why is that? Because only fat-soluble substances can enter the skin, not water-soluble ones.  Your hair stands on end and you develop 'goose bumps' because there are tiny muscles attached to the hair follicles and they contract when you are frightened or cold.