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 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