1. This is a close-up of YOU!

2. Question to ponder:
We know that red blood cells will burst in a hypotonic solution like pure water. We also know that are skin is made of cells, in fact the outer layers are stratified squamous epithelial cells. So….. Why don’t we start exploding from the outside in we we sit in a bathtub?....

3. The Largest Organ Skin is 12-15% of body weight
15-20 sq. ft ( sq. meters)
Very important barrier- moderate burns on more than 30% of skin can be life-threatening due to fluid loss and infection
A man stands silhouetted behind 21 square feet of skin substitute. Engineered from cow-tendon collagen, shark cartilage, and silicone, this skin substitute, Integra, helps surgeons close burn wounds until new skin grows in.

4. Fun Facts Where is your thinnest skin located? Thickest?
Eye lids (thinnest) soles of feet (thickest)
How many skin cells do you shed in a minute?
About 30,000-50,000 dead cells
How many pounds of skin do you loose per year?
8-10 lbs
How much of the dust in your home is dead skin cells?
50% (Globally, dead skin accounts for about a billion tons of dust in the atmosphere)
Does sweat smell?
No, it’s the bacteria 
How much bacteria is on your body?
1,000 different species AND 1,000,000,000,000 individual bacteria

5. Structures and Functions
Structures: skin, hair, nails, sweat glands and oil glands
Functions:
Barrier against infection and injury (including UV protection)
Helps regulate body temperature (sweating and shivering)
Receiver of pressure, pain, heat and cold
Maintain fluid balance
Excretes excess fluids and waste
Produce and secrete melatonin and Vitamin D

6. Hypodermis (not true layer)
2 Layers
The skin is made of 3 main layers
Epidermis
Dermis
Hypodermis (not true layer)

7. Fig. 6.1

8. Skin: The Layers

9. Epidermis: First layer
Structure: made of stratified squamous epithelium
Main cell type is a keratinocyte
Outer layer are flattened, dead cells, Inner layer is living
As lower cells do mitosis they move and push others to surface of skin
Die when too far from blood supply
As they move up, become flattened and make keratin (tough, fibrous, waterproof protein)
Takes days for new cells to reach the top
Contain nerve endings but no blood vessels (remember epithelial tissue is avascular)

10. Epidermis

12. Layers of the Epidermis

13. Layers of the Epidermis (from deep to superficial)
Stratum basale – a layer of single cells that lays on the basement membrane of the dermis. Continuously divide and push up towards the surface of the skin. Stratum spinosum – These cells are “spiny”. They have been pushed out from the stratum basale and the spines interlock together to form a support layer. Stratum granulosum – The cells of this layer are still living, but none of the nutrients reach them. These cells begin producing keratin and begin to die. Eventually, the keratin protein produced will make up the majority of the dead cells in the next two layers. Stratum lucidum –layer of dead keratinized cells is only found in areas where skin is thick, (i.e.soles of the feet) and is not found in thin skin areas, such as the forearm. Stratum corneum – Outer layer that we see and is made up of layers of dead keratinized cells. This layer is tightly bound together, and the keratin protects the underlying cells from fluid loss while keeping the skin elastic. In a process called desquamation, cells of the stratum corneum are sloughed off. Cells from the epidermis are completely shed every days, so essentially you have completely new skin every month and a half!

14. Epidermis

15. Layers of the Epidermis

16. QUESTION: What causes calluses and corns on hands and feet
QUESTION: What causes calluses and corns on hands and feet? (look it up)

18. Epidermis: First layer
Function
1) Water resistance (keratin filled dead cells)
2) Protective layer against biological/chemical assault
3) Contains MELANOCYTES (Produce pigment MELANIN which protects from UV)
4) Contains Merkel cells – attached to nerves and detect touch
5) Contains Langerhans cells –guard against toxins, microbes and other pathogens. If detected, alerts immune system

19. Epidermis

20. Skin: Dermis
Found beneath the Epidermis

21. Dermis: Second layer Structure Contains:
Made of strong, flexible connective tissue layers (areolar and dense irregular connective tissue)
Contains:
Nerves
Blood vessels
Lymph vessels
Hair follicles
Sweat glands
Muscles (attached to hair follicles)

22. Dermis Fact: This is your “hide”, when you buy leather goods (purses, belts, shoes) you are buying treated dermis of animals

23. Dermis: Second layer Function:
1) Gives skin its elasticity and strength (collagen and elastin fibers)
2) Contains Sweat glands (3000/ in2) these:
regulates body temp
Release various wastes from bloodstream
Mammary glands and ear wax glands are modified sweat glands
3) Contains Sebaceous (oil) glands (2 per hair)
release SEBUM keeping the epidermis and hair flexible and waterproof
4) Contains many sensory cells

24. Corns and Calluses
What are they?
What causes them?

25. Pressure Ulcers (bed sores)

26. Dermis Finger Prints What creates finger prints?
What are they determined by?
Why don’t identical twins have same finger prints?

27. Hypodermis bottommost layer of skin, located under the dermis.
primarily made up of adipose tissue and functions in insulation and protection.
The base of blood vessels, nerves, and some hair follicles also extend into the hypodermis.

28. Skin Color
Combination of pigments
Melanin
Carotene
hemoglobin

29. Skin color 2 types of melanin
Skin color is due mainly to the pigment MELANIN (made by melanocytes in the epidermis)
2 types of melanin
Eumelanin (comes in brown and black)
Phomelanin (pinkish-red)

30. Video- how melanin works

31. Melanoctyes

32. Skin Color
Darker skin is due to kind and amount of melanin produced (everyone has relatively similar numbers of melanocytes)
UV rays stimulate melanocytes to make more melanin (causing tanning)
Melanin protects skin cells under it from harmful UV rays

33. Skin Color Carotene Hemoglobin Red pigment of blood
yellowish pigment found in certain plant products (i.e. carrots)
Accumulates in cells of stratum corneum and subcutaneous fat
Often seen in heel and calluses of feet because where stratum corneum is thickest
Why skin can look yellowish-orange if you eat a lot of carrots
Hemoglobin
Red pigment of blood
Imparts reddish to pinkish hues as blood vessels show through skin
The less melanin, the more it shows

34. Skin Color: Albinism
FACT: Have normal number of melanocytes in epidermis but lack enzyme tyrosinase that converts amino acid tyrosine to melanin (autosomal recessive genetic defect)

35. Skin Color
Vidiligo: Autoimmune- attacks melanocytes

36. Skin Markings
Skin Markings: Freckles: Flat, melanized patches Varies with heredity or sun exposure Moles: Elevated patches of melanized skin, with hair

37. Skin Markings Birthmarks (hemangiomas) Capillary hemangiomas
Cavernous hemangiomas
Port wine stains

38. Burns: 1st Degree
Inflamed, red skin – surface of epidermis is shed

39. 2nd Degree Burns epidermis and part of dermis
Blisters form as fluid builds beneath epidermis
Can take weeks to months to heel and
will often scar

40. 3rd Degree Epidermis & Dermis is destroyed
Catastrophic loss of fluids (dehydration)
Highly susceptible to infection
Look up photos online if you would like (they can be pretty graphic)
Skin Gun