The document outlines the structure and functions of the skin, detailing its three layers: epidermis, dermis, and hypodermis, along with the specific layers of the epidermis and their roles. It discusses the production and function of melanin, the characteristics of the dermal layers, and various skin functions, including thermal control and protection against damage. Additionally, the document covers hair and nail structure, as well as the types of glands associated with the skin.

3. Skin Structure
 Epidermis :outer layer, Stratified squamous
epithelium , Provide protection to the body.
 Dermis (intermediate layer) Dense
connective tissue , role of the dermis is to
support and protect the skin and deeper layers,
assist in thermoregulation, and aid in sensation
 Hypodermis ( inner layer)Subcutaneous
tissues,
 provides the main structural support for the skin,
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.
 Stratum granulosum – 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
 Papillary layer (upper dermal region)
○ Projections called dermal papillae
 Some contain capillary loops containing
blood
 Some pain receptors and touch receptors
 Reticular layer (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 fibers give skin its toughness
○ Elastic fibers give 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 for heat loss, while constricted vessels retain
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