1. Checklist
I took notes
I labeled the layers of skin

2. Notebook Work What do you know about the layers of skin?
How does skin function? Why do we need it?
Is skin an organ?

3. Inte – = whole - gument = body covering
Integumentary System
Inte – = whole - gument = body covering

4. Skin
Skin is an organ because it consists of different tissues that are joined to perform specific activities
In adults, skin covers an area of about 2 square meters (22 square ft)
Dermatology is the branch of medicine that specializes in diagnosing and treating skin disorders

5. Structure of Skin
3 parts – thin, outer portion called the epidermis and the deeper, thicker, connective tissue called the dermis
Deep to the dermis is the subcutaneous layer also called the hypodermis
Attaches skin to underlying structures

6. Epidermis Stratified squamous epithelium and contains 4 types of cells
1) 90% is keratinocytes which undergo keratinization
Cells formed in basal layer move to surface, the cells die, slough off, and are replaced by new cells
2) 8% are melanocytes which produce melanin, the brown-black pigment that gives skin color and absorbs UV light.
5 layers and has NO blood vessels

7. Skin Color 3 pigments Emotions can also influence skin color! Cyanosis
Melanin-yellow, reddish brown, or black
Carotene-orange-yellow (carrots)
Oxygen rich hemoglobin- pigment of red blood cells
Emotions can also influence skin color!
Cyanosis
Jaundice

8. Epidermis
3) Langerhans cells-important in immune responses and easily damaged by UV light
4) Merkel cells – located in deepest part of epidermis, important in the sensation of touch

9. Dermis
Made of connective tissue containing collagen and elastic fibers that give skin the extensibility and elasticity
Stretch marks are called striae
Thick on soles of feet and palms, thin on eyelids
Dermal papillae cause ridges in epidermis=fingerprints

10. Hypodermis (subcutaneous)
Subcutaneous layer (deepest) consists of adipose tissue and other connective tissue
Serves as storage depot for fat and contains large blood vessels that supply the skin
The subcutaneous layer and dermis contain sensory neurons (sensitive to pressure)

11. Functions of Skin (6)
1. Regulation of body temp.-evaporation of sweat lowers body temp, changes in the flow of blood in the skin also regulate body temp

12. Functions of Skin (6)
2. Protection- skin covers body and provides a physical barrier that protects underlying tissues from physical abrasions, bacterial invasion, dehydration, and UV radiation
Check out the leather!!! 

13. Functions of Skin (6)
3. Sensation- contains abundant sensory nerve ending and sensory receptors that detect temp., touch, pressure, and pain

14. Functions of Skin (6)
4. Excretion- small amounts of water, salts, and several organic compounds are excreted by sweat glands

15. Functions of Skin (6)
5. Immunity- the cells in the epidermis are an important component of the immune system, which fends of foreign invaders of the body.

16. Functions of Skin (6)
6. Synthesis of vitamin D- exposure of skin to UV radiation initiates synthesis of the active form of vitamin D
Aids in the absorption of calcium and phosphorus from the G.I. Tract into the blood

17. Accessory Structures of the Skin
Hair is present on most skin surfaces except the palms of fingers soles and toes
Hair on scalp protects from sun, eyebrows and lashes protect eyes from foreign objects, and nostril hair keeps insects and foreign objects out of nose
Arrector pili muscle makes “goosebumps”

18. Accessory Structures of the Skin

19. Accessory Structures of the Skin
Cutaneous glands
Sebaceous glands (oil glands)
Sweat glands (2.5 million per person)

20. Homeostasis of Body Temp.
When it is hot, thermoreceptors (nerve endings in skin) detect and send impulses to the brain
The temp control center of brain (hypothalamus) sends an impulse to sweat glands
When the sweat evaporates, it takes the heat with it
Other ways body heat is regulated: dilating or restricting blood vessels, metabolic rate change, skeletal muscle contractions

21. Damage to the Skin
Cuts and scrapes- minor cuts, the epidermis divides to replace lost cells
Major cuts, blood flows clot forms making a scab cells beneath scab divide to fill wound
White blood cells kill invaders

22. Effects of Sunburns
As people age, the elasticity of their skin decreases=wrinkles
Exposure to UV rays can speed the process and cause burns

23. Effects of Sunburn
First-degree=cells in epidermis, redness, swelling, pain
Second-degree= cells deeper in the epidermis die, cells in the dermis injured and may die, blisters
Third-degree=cells in epidermis and dermis die. Nerve cells and muscle cells injured, skin function lost, need transplant, no pain because of nerve damage
Infection is a leading cause of death for burn victims

24. Skin Cancer UV radiation (natural or fake bake)
Damage DNA in skin cells causing cells to grow and divide uncontrollably=skin cancer
Most common cancer in the U.S.
Melanoma-deadly-one person every hour
Nonmelanoma
WEAR SUNSCREEN!
1 in 5 Americans will develop skin cancer in their lives!

25. Did You Get It? 8. What are 3 important functions of the skin?
9. What cell type is most abundant in the epidermis?
10. What pigments determine skin color?
11. What are the criteria for classifying burns as 1st, 2nd, and 3rd degree?
12. What is the single most common risk factor for skin cancer?