1. Watch This! Evolution of Skin NOVA 45 minutes Integumentary System Review all cell/tissue type terms prior to PPT!

2. Part I. The skin has important functions.
Maintains homeostasis HOW?? Keeps us together Protects us Controls water loss, temperature Contains sensory receptors Make special chemicals Releases a little waste too

3. The skin includes two distinct layers:
1) epidermis = the surface layer.  
2) dermis = The dermis is thicker than epidermis and contains a variety of tissue like smooth muscle, nerves and blood.

4. We will color later

5. EPIDERMIS Varies in thickness with the area of the body
thickest on the palms of the hands and soles of the feet
Other body regions are much thinner, ex: eyelids
4 main types of cells

6. There are four major types of cells found here. Two of them are:
#1. keratinocytes
90% of the cells
function in protection

7. #2. MELANOCYTES

8. melanin = brown to black pigment found in melanocytes
Skin color is genetically determined and results from a combination of three skin pigments
melanin = brown to black pigment found in melanocytes
2. carotene = yellowish pigment found in the epidermis and dermis
3. hemoglobin = pinkish tone in skin caused by hemoglobin found in the blood vessels found in the dermis and hypodermis

9. The Biology of Skin Color Movie
(Note: Long quiz available for A&P and AP)

10. Part II. The epidermis is divided into 4-5 layers called:
stratum germinativum (basale):
1 row of cells - Cell division occurs in this layer.
stratum spinosum : 8-10 rows of cells
stratum granulosum : 3-5 rows of cells
stratum lucidum : 3-5 rows of cells – only found in palms and soles
stratum corneum : rows of cells – TOP

11. We will color when finished with this section of notes

12. Epidermis has “stratified squamous epithelium “
cells in thickness
does not contain any blood vessels
If there are no blood vessels, then how do the cells get their nourishment and oxygen?

13. STRATUM GERMINATIVUM (bottom)
Contains the "stem cells" of the skin (undifferentiated cells that are capable of continual cell division )
These are the only cells that undergo cell division
Once the stem cell divides, the newly formed cell begins to differentiate

14. Special proteins hold cells together
As the new cells are formed, the older cells are pushed toward the surface as a unit
Why is this important?

16. STRATUM SPINOSUM (moving upward and out)
As the cells are pushed into this layer, they become slightly flattened
spines develop on edges
The spines from adjacent cells interlock near the desmosomes.
This also holds the cells together

17. STRATUM GRANULOSUM
By the time the cells reach this layer, the food supply is drastically reduced (further from blood supply)
Cells continue to flatten out ; nucleus begins to shrivel
cells die

18. STRATUM LUCIDUM
When the STRATUM LUCIDUM is present, it contains several layers of compacted cells. It looks like a wavy, clear stripe

19. STRATUM CORNIUM
Once the cells reach the STRATUM CORNIUM, they appear clear and scale-like .
The cells rub off easily
It takes, on average, about two to four weeks for the cells to move from the innermost layer to the surface.
In healthy skin, the production of new epidermal cells = the rate of destruction at the surface, therefore, your skin does not wear away completely.

20. Color now!

21. Part III. Dermis/Hypodermis
The dermis is
below the epidermis

22. The epidermis has downward projections and the dermis has upward projections
This structure helps the layers of skin ‘hold on’ to one another!

23. Function of dermis
Allows the skin to be tough and flexible.
Contains smooth and skeletal muscle. The muscles control facial expression (skeletal), hair follicles & glands and wrinkles (smooth).
Question: Is facial expression important?

24. The dermis has a blood supply! And Nerves too!

25. Some nerve fibers carry impulses from specialized sensory receptors within the dermis, to the nervous system to be processed.
Where does this begin ??

26. receptors in the dermis receive information on:
heavy pressure Light pressure Cold Hot pain

27. Receptors on our tongue

28. HYPODERMIS ( SUBCUTANEOUS LAYER)
The hypodermis is located below the dermis and is not part of the skin.
It contains blood vessels, nerves, and adipose (fat) tissue.
fibers hold everything together

29. A lot of fibers are present where the skin is closely attached to the underlying tissue (palm of hand) The number of fibers decreases where the skin is flexible and easy to move (back of hand) Try pinching each location!

30. The adipose (fat) under our skin is a heat insulator
It holds heat in and also keeps out heat from the environment.
The amount is different in different areas of the body.
It also varies from person to person.

31. Part IV. Extras…What are….Calluses and Corns?
When there is excess pressure or friction on a specific area of the skin, the rate of cell division in that area is greatly increased. This causes a build up (over development) of stratum corneum in that area and forms a corn or callus

33. BLISTERS
A blister forms when there is intense friction to an area on the surface of the skin.
A blister is a bubble (vesicle) of tissue fluid that forms between the stratum germinativum and stratum spinosum.
ROLE: Its function is to cushion the layer of reproductive cells

34. See H.O. on Special Structures and review together!
HAIR FOLLICLES AND HAIR

35. SEBACEOUS GLANDS

36. SWEAT / ECCRINE GLANDS

37. SKIN CANCER PPT + Video SKIN DEEP follows + Reading on Skin cancer and burns (A&P only)