The integumentary system defends an animal's bodily integrity---wholeness---from damage. It consists of the skin, hair, nails, claws, hooves, horns, feathers, scales, sweat glands
and nerves. It is an indispensable companion on life's journey; it is a friend worth knowing well.

- The integumentary system is semi-living armor. It is derived from numerous layers of dead cells---keratinocytes---toughened by waterproofing keratin proteins into a strong barrier. The closer to the surface, the more keratinized and stronger they are.
- This armor is divided into several basic layers. Briefly, these are: the epidermal outer layer of various types of keratinocytes, the lower dermal layer of blood
vessels , connective tissues and nerves, and the innermost layer of subcutaneous tissues that store fat, retain heat and deflect internal injury.
- The skin is the largest part of the integumentary system. Selectively permeable, it absorbs only water and certain nutrients. All other organisms, chemicals and radiation are kept out, unless the skin is punctured or a harmful substance gains entry via another opening.
- Preserving the internal conditions necessary for life---homeostasis---is a major task of the integumentary system. Regulating blood
flow to the sweat glands maintains this equilibrium. When warmth is needed, blood vessels narrow, curtailing sweating and retaining heat. If cooling is necessary, blood vessels widen, increasing sweating to cool the body via evaporation of perspiration.
Other homeostatic processes regulated by the integumentary system include water retention, nutrient absorption and synthesis, and disposal of certain wastes. - Essential information about touch, pressure, pain, heat and cold is received by receptors housed within the dermis. Without them, our understanding of our surroundings would be severely limited and we would be far less aware of our world and more susceptible to injury.
- Understanding the integumentary system reminds us of its advantages, limitations and tremendous value. It is the only one we get, and is truly worth knowing and nurturing.
Semi-Living Armor
The Basic Protective Layers: In Brief
Guardian Against Invasion
Upholder of Homeostasis
Tactile Window to the World
Solitary Soldier
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Photo Credit
elephant skin image by Philip Date from Fotolia.com

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