Functions of the Integumentary System:

• Protection: due to the many layers of the skin, it is a perfect barrier of protection. The skin helps keep out many dangerous substances as well as protecting our more fragile tissues underneath the skin.
• Regulating Body Temperature: skin has sweat glands and blood vessels to help maintain temperature homeostasis. Sweat glands allow for sweat to evaporate off the skin to reduce body temperature. Blood vessels may either constrict or dilate to help maintain body temperature or bring it down.
• Slows water loss: our body has anywhere between 50-60% water. Maintaining this percentage requires protection in the form of our skin and it's many layers
• Houses sensory receptors: below the epidermal layer of skin are touch receptors placed along the dermal papillae. Thermo receptors and pressure receptors are also housed in the dermal layer.
• Manufactures Biochemicals: skin cells help produce Vitamin D. Certain skin cells also help by producing hormone like substances to stimulate development of certain WBC's
• Excretes Waste: the skin excretes (gets rid of) waste such as urea and water through sweating
• The functions of the integumentary system are important because without it we wouldn't be able to control our body temperature or get rid of waste in out body that could possible hurt us. The big one is protection without the integumentary system everything under the skin would be in danger to outside chemicals the could be harmful to our bodies, and the skin is stopping that from coming in.

Layers of the Integumentary System:

• Epidermis ("Upon+skin"): the deepest layer containing cells that divide (strat. squam.epith). Keriatinzation: process by which cells mature as they move from deepest to most superficial layer. Outermost layer is made up of dead epidermis cells. Epidermis projects underlying tissues from water loss, injury and harmful chemicals. The pigment "melanin" protects underlying cells from UV rays.
• Dermis: connects epidermis to underlying connective tissue. Blood vessels in derma supply nutrients to skin cells and help regulate body temperature . Nerve fibers located throughout dermis; a. somatic: control glands, muscles; b.sensory: sends messages to brain. Contains hair follicles, sebaceous (oil) glands and sweat glands
• Hypodermis ("below + skin") Subcutaneous: loose connective and adipose tissue. Helps conserve body heat. Contains blood vessels that supply skin and underlying adipose tissue
• Stratum Corneum: top layer of the epidermis which is tightly packed with dead keratinized cells
• Stratum Lucidum: beneath the stratum corneum, found only in thick layers of skin like the palms and soles of the feet
• Stratum Granulosum: beneath the stratum lucidum
• Stratum Spinosum: beneath the stratum granulosum
• Stratum basale: beneath the stratum spinosum, where cells are actively reproducing
• The layers of the skin are probably the very important part of the integumentary system because they are what is actually there to protect us from the outside chemicals. They work together to be able to control what actually comes in or doesn't.

Accessory Structures of the Integumentary system:

• Hair follicle: cells from which hair originates. Keratinization occurs. Bundle of smooth muscles attached to each hair follicle. Hair color is determined by amount melanin production
• Sebaceous glands: share pore with hair follicle. Secrete oil or "sebum" which keeps hair and skin soft/ waterproof
• Nails: protective covering produced by epidermal cells and cover terminal ends of fingers and toes. Keratinized epidermal cells. Keratin in nails is harder than the keratin produced by the skin's epidermal cells
• Sweat glands: cooling and excrete waste products. Eccrine sweat glands respond to elevated body temperature
• The accessory structures are important to the integumentary because they are just another part of helping protect the skin and helping regulate body temperature such as the sweat glands. Without the glands we wouldn't be able to cool out bodies down by sweating if we were to be over heating. As well as hair follicles we wouldn't really have hair on our bodies which also helps with the protection of our skin.

Regulating Body Temperature:

• Process of Cooling Down: heat in the body is produced by chemical reaction in the cell. Skeletal and cardiac muscle cells, along with certain organs, produce lots of heat. When the body becomes too hot, there are several things to help cool us down. First, vasodilation, or the increase in the diameter of blood vessels, allows for more blood to come to the dermis of the skin. This heat escapes through the skin to the outside. Second, eccrine sweat glands are stimulated to release sweat. This sweat evaporates on the skin, carrying away heat with it
• Process of Heating Up: First, vasoconstriction occurs in the blood vessels in the dermis to reduce the loss of heat from the surface of the skin. Second, the eccrine sweat glands are kept inactive to decrease heat loss through evaporation. Third, skeletal muscles are triggered to contract sightly to increase the production of heat through chemical reactions.

Healing of Wounds:

• Process of Healing a Shallow Wound: inflammation is the first step in healing, increasing; Redness: due to vasodilation, more blood in area; Heat: large amount of blood = increase in metabolic activity and thus heat production; Swelling: increased permeability of blood vessels, more fluids into the tissue spaces; Pain: injury to neurons and increased pressure from edema. Epithelial cells within a shallow wound will simply begin dividing more rapidly to fill in the cut.
• Process of Healing a Deep Wound: deep wounds entend into the dermis or subcutaneous layer. Blood escapes in a deeper wound and will form a clot. This blood clot will try and scab over. Fibroblasts will come in and form new collagenous fibers to blind the wound together. Phagocytic cells come in and remove dead cells and debris. A scar will form once the damaged tissue is replaced and cleared out. In larger open wounds, granulations will form that are small rounded masses. These granulations have a blood vessel and fibroblasts that eventually leave just a mass of collagenous fibers in the form of a scar.