1. The Skin
COS810- FA

2. The Skin
The most extensive organ system. The skin and accessory structures, include hair, nails, glands (sweat and sebaceous), and specialize nerve receptors for stimuli (changes in internal or external environment) such as touch, cold, heat, pain and pressure. Its functions include protection or internal structures, prevention of entry of disease-causing microorganisms, temperature regulation, excretion through perspiration, pigmentary protection against ultraviolet sunrays, and production of vitamin D. The body stores about half its fat in the underlying hypodermis.

3. About the SKIN Thickest on the palms and soles Thinnest on the eyelids
Cell making factory with miles of blood vessels, millions of sweat glands, and an array of nerves within a network of fibers
The skin of an average adult is 8 to 10 lbs

4. It averages 22 square feet
Contains 1/2 to 2/3 of the blood in the body and 1/2 of the primary immune cells
Each skin contains – each inch of skin:
Millions of cells
15 feet of blood vessels
12 feet of nerves
650 sweat glands
100 oil glands
65 hair
1300 nerve endings
155 pressure receptors
12 cold and heat receptors

5. Skin Function Protection Sensation Heat regulation Excretion Secretion
Absorption

6. Protection
Protects from microorganism, injury and invasion and traps water in the body
Sebum protects the outer skin from external factors
Acid mantle is made up of sebum, lipids, sweat, and water to form a hyrolipidic film. Acid mantle has an average pH 5.5. Acid mantle is part of the skin’s natural barrier function

7. Transepidermal water loss (TEWL)
Barrier function
Protect from irritation and intercellular transepidermal water loss
Transepidermal water loss (TEWL)
Water loss caused by the evaporation on the skin’s surface
Lipid
Are protective oils that make up the intercellular cement
Intercellular cement
Found between epidermal cells
Melanin
Pigment that protects us from the sun

8. Skin Functions Sensation Heat Regulation
Sensory nerve ending in the dermis respond to touch, pain, cold heat and pressure
Heat Regulation
Through vaso constriction and vaso dilation. Arrector pili muscle contracts and causes “goose bumps”.

9. Skin Functions Excreation Secretion Absorption
Sudoriferous or sweat glands excrete persiration and detoxify the body.
Folicles and pores
Secretion
Sebacaus gland secret sebum to keep the skin soft and protected for outside elements. The skin is 50 to 70% water
Absorption
Absorption occurs through the cells, folicles, and pores of the skin

10. Epidermis, Dermis, Hypodermis

11. Epidermis
Protective covering of the body. It contains no blood vessels, but has many small nerve endings
Has 5 layers called strata
Desquamation occurs every 28, 35, 45 days

12. Dermis Is the underlying or inner layer of the skin
Is it know as the true skin
Composed of collagen protein that adds strength), reticular fiber (thin protein fibers that add support) and elastic fiber (a protein that adds flexibility
Has two layers
Papillary layer – loose connective tissue
Reticular layer – dense connective tissue

13. Hypodermis Also know as the subcutaneous layer lies beneath the dermis
Loose connective tissue such as adipose tissue insulates the body
Contains blood vessels, lymph vessels, and bases of the hair follicles and sweat glands.

14. The Skin

15. Stratum Germinativum Also know as the basal layer
Deepest layer of the epidermis live layer
Cells continuously divide - mitosis
As new cells form older cell migrate to the surface
Melanocytes are present in this layer

16. Stratum Spinosum Also know as the prickly layer
Cells continue to divide and change shape here
Enzymes are creating lipids and proteins and becomes desmosomes
Immune cells are also found here

17. Stratum Granulosum Also called the granular layer
1 to 4 layers of cells that are flat and granular shaped
Production of keratin and intercelluar lipids takes place here
These cells move upward to replace the cells shed at the stratum corneum

18. Stratum Lucidum Also know as the clear layer
This is one layer of small cells which are transparent and loosely packed to allow light to pass through
Found on the palms and soles

19. Stratum Corneum
Also know as the horny layer – scale like cells made of soft keratin
It is between 15 and 20 layers of tightly packed cells
Cells constantly turn over every 28 days
Protective layer

20. Dermis 25 times thicker then the epidermis Two layers
Papillary layer
Reticular layer
Contains blood and lymph vessels nourish the skin
Capillaries, sebaceous glands, sudoriferous glands, nerves, addition receptors and the arrector pili muscle are located here

21. Papillary Layer
Connects the dermis to the epidermis forming the epidermal-dermal conjunction
Contains elastic tissue called papillae
Dermal papillae are membranes of ridges and groves attached to the epidermis
Dermal papillae are either looped capillaries that nourish the epidermis

22. Reticular Layer Deepest layer of the dermis
Contains criss-crossing collagen fibers the form a strong elastic network
Collage, produced by fibroblasts makes up 70 percent of the dermis
Base of hair follicles, glands, blood and lymph vessels, nerve ending, collagen and elastin are found here

23. Subcutaneous Tissue Also know as the hypodermis
Loose connective tissue such as adipose tissue protects and contours the body
Acts as a protective cushion
Also contain blood vessels, lymph vessels, hair follicle base and sweat glands