Integumentary System and Body Temperature (Chap. 7)

• Skin
• Accessory structures (sweat and oil glands, hair and nails)
• subcutaneous tissue

• Two-way mechanical barrier
• Protects internal structures and organs
• Secretes important fluids
• Houses sensory receptors
• Temperature regulation
• Immune response
• Acts as a gland by synthesizing vitamin D

• Skin=Largest Organ in the body
• Two Layers: Epidermis (outer/surface layer) and Dermis (inner layer anchored to subcutaneous layer)

• Thin outer layer of the skin
• Composed of stratified squamous epithelium
• Avascular
• Five layers

• lies on top of the dermis
• has access to blood supply
• layer in which cell division takes place (2 layers)

• A tough protein
• Hardens and flattens the cells as they move toward the surface of the skin
• Waterproofing

• Surface layer of epidermis
• 30 layers of dead cells

• Lies on the subcutaneous tissue under the epidermis
• Largest portion of the skin
• Composed of dense fibrous tissue
• Contains collagen and elastic fibers (skin stretches)
• Thickness depends on where its located in body
• accessory structures (hair, nails, glands, blood vessels, nerves and muscle tissue)

an inflammation of nerves caused by the chickenpox virus develops painful skin lesions along the path of the nerve

• NOT considered part of the skin, it lies under the skin (Hypodermis)
• Composed of loose connective and adipose tissue
• Acts as insulator, (Prevents heat loss)
• Anchors the dermis to underlying structures

• Determined by many factors (genetic, physiologic, disease)
• Melanin causes skin to darken (melanocytes)
• Carotene causes skin to appear yellow
• Amount of blood in the skin affects color (e.g. flushing)
• Cyanosis skin turns blue due to poor oxygenated
• Jaundice usually seen in babies (yellow skin) too much bilirubin

• Vitilgo; loss of pigment (melanin) in certain areas of the skin, patches of white skin
• Albinism; melanocytes completely fail to secrete melanin, leaving hair, eyes, and skin white

• Unevenly distributed (sparse) over the skin
• Main function of sparseness: sense insects on the skin before they can sting us
• Somebody parts are hairless (palms of hands, soles of feet, lips, etc.)
• Eyelashes and eyebrows protect eyes from dust and perspiration
• Nasal hairs trap dust and prevent it from being inhaled into the lungs
• Hair on scalp keeps us warm

• Growth is influenced by sex hormones: estrogen and testosterone
• Color is determined by: the amount and type of melanin

• Chief parts of hair
• Shaft; part above the surface of the skin
• Shaft shape also determines hair shape (flat shaft-curly, oval shaft-wavy, round shaft-straight)
• Root; extends from the dermis to the surface

• Group of smooth muscles attached to the end of a hair follicle
• Contraction of these muscles causes the hair to stand on the end
• Goosebumps

• Alopecia; loss of hair
• Hereditary condition
• Toxins

• Thin plates of stratified squamous epithelial cells that contain keratin
• Structures include: free edge, nail body, and nail root.

• Two major exocrine glands
• Sebaceous- oil glands, associated with hair follicles, secrete sebum
• Sebum lubricates and helps waterproof the hair and skin and inhibits growth of bacteria on surface 
• Sudoriferous-Sweat glands, located in the dermis, secrets sweat.
• Apocrine sweat secreted by hair follicles and axillary/genital areas. 
• Eccrine sweat glands located throughout the body but not associated with hair follicles

• Normal body temp: 98.6°F (97-100°F okay)
• Maintained by balancing (thermoregulation) heat production and heat loss.

• produced by metabolizing cells
• produced by muscles and the liver

• 80% of heat is lost through the skin
• Radiation-heat is lost from a warm object (body) to cooler air surrounding it.
• Conduction- loss of heat from warm object to a cooler object when it comes in contact
• Convection-loss of heat by air currents moving over the surface of the skin
• Evaporation-when a liquid becomes a gas (ex. sweat)

• Normal body temp. is set by body thermostat in the hypothalamus.
• Heat is lost through sweating and vasodilation
• Heat is conserved by vasoconstriction and produced by shivering

• Classification: Thickness of burn, Partial (first and second degree) and Full (third degree) burns. Rule of nines to evaluate burns (%)
• Short term effects: fluid and electrolyte losses, shock, inability to regulate body
• Long term effects: scarring-loss of function

• Dead burned tissue, forms a thick, inflexible, scablike layer over burned surface
• Breeding ground for bacteria
• Escharotomy

• Thinning epidermis
• Melanocytes decrease
• Dermis becomes thinner
• Skin becomes more fragile
• Subcutaneous tissue circulation decreases
• Adipose tissue decreases in subcutaneous layer.