4 - Skin

• -largest organ
• -7600 cm²
• -7% body weight
• -0.5-0.6 cm thick

• -prevents dehydration (impermeable barrier)
• -regulates temp (sweat, blood vessels)
• -protects against microorganisms/pathogens (impermeable barrier, secretions)

• 1. epidermis
• 2. dermis
• 3. hypodermis

keranitnized stratified squamous epithelum

• -are the great majority of epidermal cells
• -synthesizing keratin

• -synthesize melanin
• -uv protection

• -macrophages
• -act in immune response against toxins, microbes, ect, that penetrate skin

-receptors for touch

• stratum basalis -> stratum spinosum -> stratum granulosum -> stratum corneum
• (this process takes 30-40 days)

then exfoliation occurs

• papillary layer
• -looser CT
• -more elastic

• reticular layer
• -dense irregular CT
• -less elastic

orientation of collagen bundles

(surgical cuts are made along these "langer lines" to reduce scarring and shit)

elastic patterns in dermis (eg: finger prints)

blood vessels, nerves, bases of glands, hair follicles, and arrector pili muscle (goose bumps!)

• -adipose tissue
• -fatty connective tissue (high cell/ecm ratio)
• -blood vessels

sweat glands + blood vessels

• -sweat: evaporative cooling
• -lose heat by vasodilation
• -conserve heat by vasoconstriction

merocrine (eccrine), some apocrine glands

simple alveolar glands

secretion into hair follicle or pours

oil + cell debris

a disease of the epidermis

• -malignant skin tumor involving cancerous changes of basal skin cells
• -caused from exposure to sunlight or uv radiation
• -95% cure rate when caught early

• -cancerous changes to middle portion of epidermis
• -malignant, more aggressive than basal cancer, but still relatively slow growing
• -more likely than basal cell cancer to metastasize
• -requires surgical removal

• -malignant skin cancer that involves the skin cells that produce pigment (melanocytes)
• -increases with age
• -number 1 cause of cancer death in women age 25-30

affected area: epidermis

-red, painful, dry (sunburn)

affected area: dermis + epidermis

-red, blisters, swollen, painful

• no pain!
• affected area: "full thickness"
• -epidermis + dermis
• -includes epidermal derivatives

-dry, leathery, black, white, brown, yellow, swelling