Skin An Essential Organ

provides the main structural support for the skin, as well as insulating the body from cold and aiding shock absorption

3. Skin Structure
Epidermis:outer layer, Stratified squamous
epithelium , Provide protection to the body.
Dermis(intermediate layer) Dense
connective tissue ,roleof thedermisis to
support and protect theskinand deeper layers,
assist in thermoregulation, and aid in sensation
Hypodermis(inner layer)Subcutaneous
tissues,
provides the main structural support for theskin,
as well as insulating the body from cold and
aiding shock absorption

4. Skin Structure
Summary of layers from
deepest to most superficial:
Stratum basale
Stratum spinosum
Stratum granulosum
Stratum lucidum
Stratum corneum

6. Layers of the Epidermis
Stratum basale
Deepest layer of epidermis
Cells actively undergoing cell division
New cells are pushed upward to become the more
superficial layers
Stratum Spinosum
–intermediate layer .responsible for the skin strength and
flexibility.
Stratumgranulosum–prevent fluid loss from the body

7. Layers of the Epidermis
Stratum lucidum
Formed from dead cells of the deeper layers
Occurs only in thick, hairless skin of the palms
of hands and soles of feet
Stratum corneum
Outermost layer of epidermis
Scale-like dead cells are filled with keratin
which is a protective protein preventing water
loss from skin
barrier that prevents unwanted materials from
entering.

8. Keratinization
Cells migrate to the epidermis where eventually they
fall off.
As they move upward, keratin is added.
The cells in the epidermis contain a lot of keratin which
resists damage.
Distinct layers of cells are called strata.
A cell takes ~ 40 –56 from creation to sloughing off

9. Melanin
Pigment (melanin) produced by
melanocytes
Melanocytes are mostly in the stratum
basale
Color is yellow to red to brown to black
Amount of melanin produced depends
upon genetics and exposure to sunlight

10. Large amounts of melanin occur in some
regions like freckles, moles, and nipples.
Less melanin occurs in the lips, hands,
and soles of the feet.
All races have the same number of
melanoctyes! The amount of melanin
produced is determined by genetics.

11. Dermis
Two layers
Papillarylayer(upper dermal region)
○Projections called dermal papillae
Some contain capillary loops containing
blood
Some pain receptors and touch receptors
Reticularlayer(deepest skin layer)
○Blood vessels
○Sweat and oil glands
○Deep pressure receptors

13. Dermis
Overall dermis structure
Collagen and elastic fibers located throughout the
dermis
○Collagen fibersgive skin its toughness
○Elastic fibersgive skin elasticity
Dermal papillae –extend toward the epidermis and
deliver nutrients, remove waste products (sweat ,
urea and uric acid) and aid in regulating body
temperature.

14. Normal Skin Color
Melanin
Yellow, brown, or black pigments
Carotene
Orange-yellow pigment from some
vegetables
Hemoglobin
Red coloring from blood cells in dermal
capillaries
Oxygen content determines the extent of red
coloring

15. Hypodermis
Subcutaneous tissue (hypodermis)is
deep to dermis
Not part of the skin
Anchors skin to underlying organs, bones and muscles
Contains half of the body’s fat; acts as padding and
insulation.

16. Skin Functions
Thermal control –regulates body temperature
dilated vessels allow forheat loss, while constricted vesselsretain
heat
Waterproofing–contains lipids to prevent drying out
Excretion of waste –urea and uric acid secreted in sweat
Makes vitamin D –modifies cholesterol molecules in skin and
converts it to vitamin D
Mechanical/Chemical damage –Provides a protective barrier
against mechanical, thermal and physical injury and hazardous
substances.
Bacterial damage –skin secretions are acidic and inhibit bacteria.
Ultraviolet radiation –melanin produced to protect from UV
damage

17. What Else Comes from the Epidermis?
Hair
Glands
Nails

18. Hair Structure
Shaft
○Superficial portion
Root
○Below the surface
Cuticle
○Outermost layer of hair
Hair develops in follicles
○Downward continuation of epidermis

19. Functions of Hair
Protection
Thermoregulation
Sensory

20. Hair Structure

21. Growth of Hair
At the base of the follicle, hair papilla
○Contains blood vessels and nerves
Nourishes hair
Bulb
○Contains matrix –epithelial cells
responsible for growth
Contains melanocytes

22. Glands
Sebaceous glands
○Connected to hair follicles
○Secrete a waxy, oily substance
(sebum)

23. Sebaceous Glands

24. Glands
Sweat glands
○Found just about everywhere
○Produce “perspiration”
Water, salt. Wastes
○Function –cooling of the body
Scent Glands
○Specific type of sweat gland
○Found near hair follicles
○Develop at puberty

25. The Skin with Sweat Glands

26. Nail Structure
Nail body
Free edge
Nail root
○Matrix

27. Nail Structure