1. Structure of the Skin Divided into 3 basic layers: 1. Epidermis
3. Subcutaneous tissue

2. Epidermis: top level Made up of 5 cell layers (from bottom to top):
Basal (deep)
Spinus
Granular
Lucidum
Corneum (superficial)

3. Basal cell layer Deepest layer
Cells are continually dividing to produce new skin cells (millions daily)
These cells move towards the skin surface,
Blood is provided by the dermis below

4. Spinus cell layer
Cells above the basal cell layer become more irregular in shape

5. Granular cell layer
Cells are moving away from the blood supply, the cells begin to flatten and die
Keratin begins to form in the cells.

6. Lucidum cell layer Clear-ish layer of skin
Only found where the skin is hairless and extra thick
lots keratin to provide water-repellent properties

7. Stratum Corneum Layer of skin we SEE
Made up of overlapping squamous cells
Cells are dead and constantly shedding
These cells provide the tough and watertight function of skin

9. Dermis layer “hide”
Contain many of the structures that are found within our skin.
Arteries and veins run through this layer

10. Structures of the Dermis
Cutaneous glands
Sebaceous gland
Sweat glands
Hair
Nails
Nerves
Collagen and elastin fibers

11. Cutaneous Glands
All exocrine glands that release their secretions to the skin surface via ducts
2 groups:
Sebaceous glands
Sweat glands

12. Sebaceous Glands Glands that secrete sebum (oil)
Ducts empty out into hair follicles

13. Characteristics of Sebum
Lubricant that keeps skin soft and moist
Prevents hair from becoming brittle
Chemicals that kill bacteria
The gland becomes highly active during adolescence

14. Acne Sebaceous gland’s duct becomes blocked by sebum
A whitehead forms on skin surface.
If the material oxidized and dries, it darkens and becomes a blackhead

15. Sweat Glands More than 2.5 million per person 2 types:
Eccrine: found all over the body
Apocrine: found only in genital and axillary regions

16. Sweat
Made up of water, NaCl, vitamin C, metabolic wastes, and lactic acid
Ducts that lead to the surface of the skin are called pores

17. Sweat Gland and Pore

18. Homeostatic Uses of Sweat
Supplied with nerve endings that cause them to secrete sweat when outside or body temperature is too high

19. Hair Earlier humans had more hair for insulation and self defense
Current uses for hair:
Guarding head against minor impact
Shielding the eyes
Keeping particles out of respiratory organs

20. Structure of the hair Root: enclosed in the follicle
Shaft: projecting out of the scalp
Hair bulb matrix: Inferior end of the follicle. Where new hair is formed.

21. Hair Follicles Where hair forms and attaches to the body
Made of 2 layers:
Inner epidermal layer: forms the hair
Outer dermal sheath: supplies blood and reinforces hair to body

22. Arrector pili Small bands of smooth muscle cells
When contracted the hair is pulled upright, dimpling the skin surface “goosebumps”

23. Nails Made up of keratinized skin cells
Scale-like modification of the epidermis that corresponds to the hoof or claw of other animals

24. Subcutaneous layer The innermost layer of the skin Composed of fat
thickness varies upon body region
This layer performs 2 major functions:
energy source for the body
helps to insulate the body against temperature.