What type of tissue you observe Friday?

Integumentary System

Integument: any covering or enclosure-Derma: skin

Dermatologist?

Stratified squamous epithelial cells

Components

• Skin • Accessory features:

– Sudoriferous glands (sweat glands)– Sebaceous glands (oil glands)– Hair– Nails

Skin accounts for how much of your body weight?

• Average = 15%, 8 pounds

What is the skin’s square footage?

• Covers up to 22 square feet (2 square meters) if all spread out

Did you know?

• As a fetus, you had webbed hands and feet

apoptosis

Function

• Protection– Cushioning, insulation, first defense

• Healing• Synthesizes vitamin D when exposed to UV• Sensory reception• Maintain homeostasis

– Temperature, Waste, water• Window into inner workings…examples:

– Jaundice, anemia, shock, etc

Where is the thinnest skin located?

• Eyelids• 0.01 to 0.015 cm thick

Where is the thickest skin found?

• Palms and heels• About 0.46 cm thick

Labeling

Two types of tissue

Epidermis• Moisture proof• Protective outer covering• Thin• Avascular• Outer layer = dead cells• Melanocytes – make

melanin• Constantly shedding

Dermis• Connective tissue• Makes up majority of the

skin• Provides support• Strength and suppleness• “true” skin – stays the same

throughout entire life

Epidermis and dermis of (a) thick skin and (b) thin skin(which one makes the difference?)

Epidermis: layers (on left) and cell types (on right)

Epidermis…

• Stratum germinativum• Cells die as move upwards• Stratum corneum• Cells undergo keratinization

– Tough protein– Deposited within a cell– Hardens and flattens the cells– Makes skin water-resistant

Dander

• Dead, sloughed off cells• When clump together = dandruff

How much skin will you lose over your lifetime?

• About 40 pounds of skin cells are shed

How often is your outer layer of skin “turned over”?

• monthly

Dermis

• Collagen + elastin in a gel-like substance• Strong and stretchable

Stretch marks: striae

• Dermal tearing• Extreme stretching of the skin

Blister

• Separation of epidermal and dermal layers by a fluid-filled pocket

Dermis…

• Also contains:– Blood and lymph vessels– Nerve endings– Hair follicles– Sweat and sebaceous glands– Collagen and elastin

tattoos

Subcutaneous Layer

• Not part of the skin = hypodermis• Loose connective tissue and adipose• Insulates from extreme temperature changes

in external environment• Anchors skin to underlying structure

– Some areas have no subcutaneous layer – connect directly to bone…

Subcutaneous injection

• Rich supply of blood vessels