1. Integumentary System

2. The Skin
It is the largest organ in the body, although it is easily infected because of its location.

3. Functions Protection- Outer most wall of defense
a. Physical barrier: abrasions, dehydration, UV radiation (aids in production of vitamin D)
b. Biological barrier: microbes (bacterial, fungal, etc.)
2. Sensation-
a. Skin acts as a big sensory organ (temp, pain, pressure)
b. Keeps body informed of changes in environment

4. 3. Temperature Regulation- a. Regulates sweat secretions b
3. Temperature Regulation- a. Regulates sweat secretions b. Regulates blood flow c. Goose Bumps
PST…

5. The Structure of Skin
Epidermis – superficial, thin in some areas of the body and thicker in others
Dermis – intermediate, thicker, connective tissue layer.
Subcutaneous layer (hypodermis) – deep tissue layer that attaches skin to underlying structures.

6. Epidermis Its avascular (epithelium) Types of cells
Keratinocyte – cells that produce keratin (protein)
Most abundant cell in epidermis
Keratinization – process of filling skin cells with keratin as they migrate to the surface. The process takes about 2-4 weeks.
Melanocyte (also found in dermis) – cells that produce melanin – pigment used to color skin, eyes and hair.

7. Epidermis Continued
Langerhans cells- part of the immune response; easily damaged by UV rays
Merkel cell (found in the deepest layer of hairless skin) – thought to function in sensation of touch.

8. Epidermis is Composed of Five Sublayers
Superficial (outer)
Stratum cornea
Stratum lucidium*
Stratum granulosum
Stratum spinosum
Stratum basale
Deep (inner)

9. Layers of the Epidermis (from inside out)
Stratum basale
Superficial to the dermis
Cells undergoing mitosis
New cells become the more superficial layers
Dermis and Stratum Basale form wavy border

10. Epidermis Layers Stratum spinosum Stratum granulosum 8 to 10 layers
Production of Keratin begins
Stratum granulosum
2 to 5 layers thick
Cells are becoming flattened
Continue to fill with keratin as organelle’s stop functioning

11. Layers of the Epidermis
Thin Skin
Layers of the Epidermis
Stratum lucidum
Formed from dead cells of the deeper strata
Prominent in thick, hairless skin of the palms of hands and soles of feet

12. Epidermis Layers Stratum corneum 30 layers of dead cells
Cells are completely full of keratin
As new cells ascend old cells slough off

13. In Epidermis Layer Melanin Pigment (melanin) produced by melanocytes
Melanocytes are mostly in the stratum basale
Amount of melanin produced depends upon genetics and exposure to sunlight