Integumentary System

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

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

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

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.

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.

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.

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

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

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

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

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

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