Skin (Part 1)

Aaron Aujla Adam Gordon Rand Hardy Matt Kenny Nicholas Kokkinis Hanneline Rogeberg James Siena Keith Sonnier

Skin is the soft outer covering of vertebrates. (from Latin cutis, skin). In mammals, the skin is an organ of the integumentary system made up of multiple layers of ectodermal tissue, and guards the underlying muscles, bones, ligaments and internal organs. ‪[1]‬

The skin interfaces with the environment and is the first line of defense from external factors. Its other functions are insulation, temperature regulation, sensation, and the production of vitamin D folates. Severely damaged skin may heal by forming scar tissue. This is sometimes discoloured and depigmented. The thickness of skin also varies from location to location on an organism. In humans for example, the skin located under the eyes and around the eyelids is the thinnest skin in the body at 0.5 mm thick, and is one of the first areas to show signs of aging such as "crows feet" and wrinkles. The skin on the palms and the soles of the feet is 4 mm thick and the thickest skin in the body.

Fur is dense hair. ‪[8]‬ Primarily, fur augments the insulation the skin provides but can also serve as a secondary sexual characteristic or as camouflage

Skin performs the following functions:

Protection: an anatomical barrier from pathogens and damage between the internal and external environment in bodily defense; Langerhans cells in the skin are part of the adaptive immune system.‪ [3] [4]‬

Sensation: contains a variety of nerve endings that react to heat and cold, touch, pressure, vibration, and tissue injury; see somatosensory system and haptics.

Heat regulation: the skin contains a blood supply far greater than its requirements which allows precise control of energy loss by radiation, convection and conduction. Dilated blood vessels increase perfusion and heatloss, while constricted vessels greatly reduce cutaneous blood flow and conserve heat.

Control of evaporation: the skin provides a relatively dry and semi-impermeable barrier to fluid loss.‪ [4]‬ Loss of this function contributes to the massive fluid loss in burns.

Aesthetics and communication: others see our skin and can assess our mood, physical state and attractiveness.

Storage and synthesis: acts as a storage center for lipids and water, as well as a means of synthesis of vitamin D by action of UV on certain parts of the skin.

Excretion: sweat contains urea, however its concentration is 1/130th that of urine, hence excretion by sweating is at most a secondary function to temperature regulation.

Absorption: the cells comprising the outermost 0.25–0.40 mm of the skin are "almost exclusively supplied by external oxygen", although the "contribution to total respiration is negligible".‪[9]‬ In addition, medicine can be administered through the skin, by ointments or by means of adhesive patch, such as the nicotine patch or iontophoresis. The skin is an important site of transport in many other organisms.

Water resistance: The skin acts as a water resistant barrier so essential nutrients aren't washed out of the body.

Keith Sonnier was born in 1941 in Mamou, Louisiana.

Rand Hardy was born in 1944 in Bryn Mawr, Pennsylvania.

James Siena was born in 1957 in Oceanside, California.

Hanneline Rogeberg was born in 1963 in Oslo, Norway.

Matt Kenny was born in 1979 in Kansas City, Missouri.

Aaron Aujla was born in 1986 in British Columbia, Canada.

Adam Gordon was born in 1986 in Minneapolis, Minessota.

Nicholas Kokkinis was born in 1991 in New York, NY.