Integumentary System

The Skin You’re In20 square feet

40 lbs shed in your lifetime8 lbs

The Skin

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

Functions1. Protection-

Outer most wall of defensea. 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 secretionsb. Regulates blood flow c. Goose Bumps

PST…

cutaneous membrane

Remember: Membranes must have 2 tissue layers

What are the two layers found in epithelial membranes?

Epithelium and connective

What are the two layers found in skin?Epidermis and Dermis

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.

What type of tissue must that be?

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

Deep (inner)» Startum basale » Stratum spinosum» Stratum granulosum» Stratum lucidium* » Stratum cornea

Superficial (outer) Bob’sSisterGraceLovesCorn

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

Thin layer

Epidermis Layers

• Stratum spinosum– 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• Stratum lucidum– Formed from dead

cells of the deeper strata

– Prominent in thick, hairless skin of the palms of hands and soles of feet

Thin Skin

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