1. The Integumentary System

2. Integumentary System Includes:
Skin (cutaneous membrane)
Subcutaneous tissue below the skin
Accessory Structures
Sweat glands
Sebaceous or oil glands
Hair
Nails

3. Layers Of The Integument
Epidermis – outer, most superficial layer
Dermis – just deep to the epidermis
Hypodermis - both epidermis and dermis are anchored to the body by a subcutaneous tissue, or “fatty tissue,” called adipose tissue.

4. Epidermis
Key points-
“Avascular” meaning it has no blood supply of its own
Oxygen and nutrients diffuse from the underlying dermis
The epidermis is keratinized layers of cells.
Keratinized – hardened/dry cells “dead”
Five structurally different layers can be identified:

6. First Layer of the Epidermis
Stratum basale (germinativum) or “base”
The deepest layer of the epidermis (closest to the dermis).
It is found close to the dermal blood supply.
Basal cells are the stem cells of the epidermis. Their mitotic activity replenishes the cells in more superficial layers as these are eventually shed from the epidermis.
The renewal of the epidermis takes about 3 to 4 weeks in humans as millions of cells are produced daily.

7. Cells die as they are pushed away from the source of nourishment.
Cells undergo keratinization as a tough protein, Keratin, is deposited within the cell. Keratin hardens and flattens the cells as they move outward and it waterproofs the skin.
Epidermal Ridges feed into the Dermal Papillae (increased surface area

9. Stratum Spinosum 2nd layer, just superficial to stratum basale
Receives cells from basale that just went through mitosis.
8-10 layers of keratinocytes (cells that make keratin)
Contains Langerhans cells – defense against microorganisms

10. Stratum Granulosum – “grainy layer”
3rd layer, just superficial to stratum spinosum
Cells have stopped dividing and started making Keratin – (tough/fibrous protein that is the basic structural component of hair and nails)
Cells start to “die”
Cell membranes thicken and become less permeable, they dehydrate, nuclei and organelles die off and the cell dies….

11. Stratum Lucidum – “clear layer”
“4th layer” - extra layer
Found in the skin of palms and soles
Cells are flat, densely packed, and keratinized

12. stratum corneum About 30 cells thick – keratinized
¾ of the overall thickness of the epidermis
Provides the majority of the protection of the body, compared to the other layers
Typically dry and needs lubrication from oil glands

13. stratum corneum Water-resistant - NOT water-proof
What happens to your skin if submerged in fresh water for prolonged period of time?
Water, being hypotonic to the environment in the cells of our skin, will force water to move into the cells, causing it to swell.
Opposite – saltwater is hypertonic and will draw water OUT of the cells of the epidermis

15. Concept check – pg 157 (4 questions)
In your notebook:
Title –Epidermal Concept Check
Write in FULL sentences!
Answer completely!

16. What causes skin to regenerate?
Hormone = EGF ; Epidermal Growth Factor
Produced in salivary glands and small intestine
Promotes mitosis
Increases keratin production
Stimulates epidermal repair (cut/scrape)
What is a skin graft?
How are they created?

17. What does this process LOOK like to you?
TWO options 
1 - Paragraphed explanation of how this process works OR
2 – Sketch / Diagram of how this process works (with minimal writing)

18. Whether writing or sketching, you must include:
hormone involved and where its produced
What does this hormone cause to happen?
The idea of skin grafts and how they can be produced.

19. Pigments contributing to Skin Color
Carotene
Orange-yellow pigment
Most apparent in stratum corneum of light-skinned people
Converted to Vitamin A = important for maintenance of epithelial cells
Carrots, squash, pumpkin 

20. Pigments contributing to Skin Color
Melanin
Brown, yellow/brown, black pigment
Produced by melanocytes
Approx melanoctyes per mm2
NOTE: Cheeks, forehead, nipples, scrotum (males), labia majora (females) have higher concetrations of melanocytes = approx 2000 per mm2

21. 1- Melanocytes produce melanin
2- Travels in intracellular vesicles called melanosomes
3- Transferred to keratinocytes (keratinized cells)
**Eventually the melanosomes are destroyed by lysosomes

22. Pigments contributing to Skin Color
Melanocytes
UV rays trigger melanin production
Melanin congregates around the nuclei of cells = Protection from harm
Increased levels of UV rays = darker skin = bodies way of protecting itself
THEN WHY MUST PEOPLE RE-TAN?

23. THEN WHY MUST PEOPLE RE-TAN
THEN WHY MUST PEOPLE RE-TAN? (Even though we know its not good for you) 
Since melanosomes are consumed by the lysosome of the surrounding cells. This means these “pigment” molecules disappear, which is YOU losing that tan!

24. Pigments contributing to Skin Color
Pale-skinned
Melanosomes stay deep (basale and spinosum)
Less pigment is produced
Dark-skinned
Melanosomes travel more
superficial (granulosum)
More pigment is produced

25. Pigments contributing to Skin Color
Hemoglobin
Found in red blood cells
Hemoglobin binds to oxygen = red
Capillaries in the dermis are more easily seen in pale-skinned people (lack of melanin)

26. Pigments contributing to Skin Color
Hemoglobin
HEAT = Dilation of capillaries = more red
COLD = Constriction of capillaries = white
CYANOSIS (blue color) = lack of oxygen to tissues
 extreme cold
 asthma

27. UV RAYS = steroid production
Not ALWAYS harmful!
Stimulates production of cholecalciferol (Vitamin D)
Liver converts it to hormone called calcitrol
Calcitrol, utilized by the kidneys, is essential for normal calcium and phosphorus absorption
Calcium and phosphorus = crucial for bone strength!

28. Concept Check – pg 161 Concept Check Page Write in FULL sentences!
Answer completely!

29. The Hypodermis – deepest layer
-Sub-cutaneous layer
-Connects to dermis via collagen and elastin fibers
-Houses fat and blood vessels
-Made up of Adipocytes – cells that specialize in accumulating and storing fats
(Adipocytes + connective tissue = adipose tissue)
Purpose:
Thermoregulation – fat is a heat insulator
Energy reserve – fat can be put back into circulation via the veins/arteries found throughout the adipose tissue

30. Directions-
GOAL - create a “Cinquain” for the topic of the hypodermis on the bottom-half of the handout provided. Directions are on your “literacy strategies” page of your notebook (will go in notebook)
Come show me to get stamped!