More on skin


Knitted together with a variety of sturdy cells, the skin protects the soft tissues within the body. Like a frontier of civilization, it is a bastion, a place at which skirmishes are fought, and invaders resisted, or first and final line of defence. Here are 7 of the most important functions.

  1. Regulation of body temperature. In response to high environmental temperature or strenuous exercise, the evaporation of sweat from the skin surface helps lower a raised body temperature to normal. In response to low temperature, production of sweat is decreased to help conserve heat. Changes in the flow of blood to the skin also help regulate body temperature.
  2. The skin covers the body and provides a physical barrier that protects underlying tissues from physical abrasions, bacterial invasion, dehydration, and ultraviolet (UV) radiation.
  3. The skin contains lots of nerve endings and receptors that detect stimulation related to temperature, touch, pressure and pain.
  4. As well as removing heat and water from the body, sweat also is the vehicle for removal of a small amount of salts, and several organic compounds.
  5. Certain cells of the epidermis are important part of the immune system, which fend off foreign invaders outside the body.
  6. Blood reservoir. The dermis of the skin houses extensive network of blood vessels which carry 8% to 10% of the total blood flow in a resting adult. During moderate exercise skin blood flow may increase, which helps remove heat from the body. During hard exercise, the blood vessels constrict (narrow) to enable more blood to circulate to contracting muscles.
  7. The Synthesis of Vitamin D. Vitamin D is a group of closely related compounds. The synthesis of Vitamin D begins with activation of a precursor molecule in the skin by UV rays in sunlight. Enzymes in the liver and kidneys then modify the molecule finally producing calcitriol the most active form of vitamin D. Calcitriol contributes the homeostasis of body fluids by aiding the absorption of calcium in foods. Calcium is necessary for bone growth and strength.

Avoiding Vitamin D Deficiency

During most of the year, an hour per week in the sunlight with the hands, arms, and face exposed, meets the body’s needs for the activation of the Vitamin D precursor necessary for Calcitriol production to aid absorption of calcium from the gut.