Integumentary System

Skin

• surface area of 1.2-2.2 square meters
• weighs 9-11 lbs
• 7% of total body weight

Functions of Skin

• 3 types of barriers
• Chemical, Physical, Biological

Chemical

• skin secretions
• melanin

Skin Secretions

• Acid mantle
• Sebum
• Human defensin
• Cathelicidins

Melanin

• Provides a chemical pigment shield to protect from UV damage

Physical

• continuity of skin
• hardness of the keratinized cells
• If too thick, lose suppleness and agility
• If too thin, not as protective
• Waterproofing glycolipids

Physical

• Lipid soluble items can penetrate
• oxygen, carbon dioxide, fat-soluble vitamins, steroids
• certain plant chemicals (poison oak and poison ivy)
• organic solvents (acetone, dry-cleaning fluid, paint thinner
• salts of heavy metals (lead and mercury), & drug agents

Biological Barriers

• Langerhans' Cells
• active elements of the immune system
• for immune response to be activated, the antigens must be presented to lymphocytes (WBCs)
• the Langerhans' cells play this role in the epidermis

Biological Barriers

• Macrophages in the dermis
• DNA molecules
• electrons absorb radiation and transfer it to the nuclei, which heat up and vibrate to dissipate heat to surrounding water molecules

Other Functions

Body Temperature

• regulates temperature within homeostatic limits
• as long as air is cooler than internal temperature, the skin surface loses heat to the cooler objects in its environment

Body Temperature

• Sweat continuously, just unnoticeable
• when body temp rises, so does sweat production
• can lose up to 12L of water per day
• evaporation of sweat cools the body to prevent overheating

Body Temperature

• when the external environment is cold, blood vessels constrict, this causes the warm blood to bypass the skin temporarily
• this slows passive heat loss, to conserve heat within the body

Cutaneous Sensation

• richly supplied with cutaneous sensory receptors (part of the nervous system)
• Meissner's corpuscles
• Merkel discs
• Pacinian corpuscles
• Hair Follicle Receptors

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