• the skin, which is the largest organ of the body; also the larges emunctary (or organ of elimination)
• its appendages: sweat glands, sebaceous oil glands, hair and nails

• waterproof, stretchable, washable, automatically repairs small rips and burns, and is garuneteed to last a lifetime with reasonable care
• covers the entire body, and is about 7% of the total body weight
• very complex: (1) more than 500,000 cells (2) varies in thickness - thickest at the palms of the hands and soles of the feet

• superficial layer of thick epithelium (keratinized, stratified, squamous cells)
• the deep epidermis undergoes contiuous mitosis, pushing cells by the tume they reach the surface, they are dead and filled with keratin
• brand new skin every 35-45 days; the production balances the loss at the surface of the skin

• deep to epidermis
• fibrous CT layer that is strong and flexible
• made up of collagen, elastin and reticular fibers
• contains a high amount of nerve fibers and blood vessels; can hold up to 5% of blood volume of the body
• heightens when there is a need for cooling the body
• lessens when blood is needed elsewhere

• the fatty or adipose layer deep to the dermis that shares some of the skin's functions
• this layer is also known as subcutaneous tissue or superficial fascia
• functions to isolate the body from cold, softens any impact, and acts as the body's main energy reserve
• NOT PART OF THE INTEGUMENTARY SYSTEM

touch receptor

part of the dermis

receptor for pressure and vibration

part of the dermis

heat receptor

part of the dermis

krause's corpuscle

receptor for cold

part of the epidermis

receptor for pain

part of epidermis

• cushions and insulates the deeper body organs, and protects the body from mechanical damage
• protection from harmful chemicals, thermal damage and invading bacteria
• waterproof epidermis, preventing unnecessary loss of water across the body surface

• the skin acts as a ______ system with the loss of urea, salts, and water through sweating
• the skin screens harmful UV rays and its epidermal cells; uses these rays also to sinthesize (Vitamin D) -> hormonal control, creation in enzymes helps lower _______
• contains sense orgns callded sensory receptors that are associated with afferent sensory nerves (they sense _____, _____, _____ and _____

• mini-excretory
• inflamation
• they sense touch, pressure, temp and pain

1. hair and hair follicles (epidermal)
2. sebaceous glands and follicles (dermal)
3. sweat glands (dermal)
4. nails (epidermal)

• located in the epidermal layer
• hair is 3 concentric layers of keratinized cells
• follicles are tubular invaginations of epidermis from which the hair grows
• hair color is determined by melanocytes at the base of the follicles

sebaceous glands and follicles

• found in the dermal layer
• these are the skin's oil glands (secrete sebum)
• found everywhere in the body except the palms and soles
• functions by hormonal stimulation (especially androgens)
• softens and lubrictes hair and skin
• helps the slow loss of water across skin
• has bacteria-killing action
• when the gland is blocked, acne is produced (whitehead, blackhead, pimple formation)

sweat glands

• found in the dermal layer
• everywhere but nipples and part ofthe external genitalia
• sweating prevents the overheating of the body
• heat induced sweating gstarts at the forehead and spreads inferiorly
• emotion induced sweating ("cold sweat") begins on palms, soles and axillae (then spreads to other areas)
• palms, soles and axillae -> innervated by sympathetic chonlinergic post-synaptic fibers
• sweat is primarily a filtration of blood, so it is 99%  water with some salts and metabolic wastes
• sweat is acidic so it is bacteria-static (retards the growth of bacteria on skin)
• MAIN cooling system & has an anti-bacterial function

• found in the epidermal layer
• modified, hardened version of the epidermis
• protective mechanism, grasp small delicate objects
• some examples: clubbing (heavy smoking), spoon nail (nutrient deficiency), and beau's line (lack of iron)

• psoriasis - inflamatory of the skin (steroid-treatment)
• auto immune

• squamous cell carcinoma: 2nd most common
• basal cell carcinoma: most common
• malignant melanoma: very aggressive, rapidly growing (shape, color, diameter evolving)