Test Your Knowledge

The skin has several important functions, including:

• Protection. The skin serves many protective functions. It prevents infectious agents, such as germs, and other harmful substances from entering the body. It also shields internal organs, muscles, nerves, blood vessels and other structures from the sun’s harmful ultraviolet rays and protects the body from injury.
  
  
• Preventing the loss of essential fluids and substances. The skin prevents the loss of blood, water, other life-sustaining fluids, fat, and vitamin D.
  
  
• Regulation of body temperature. The skin contains blood vessels that expand and contract in response to a person’s body temperature. Sweat is a natural response to feeling hot.  The evaporation of sweat on the skin causes a reduction in body temperature. When a person is cold, the blood vessels in their skin narrow. As a result, the skin becomes pale and cold. Because the blood flow in the skin decreases, the person loses less heat. This conserves the heat for the body’s vital organs.
  
  
• Sensation. The skin senses painful and pleasant stimuli. It contains sensory nerves that send messages to the brain about dangers, such as injury, extreme heat or extreme cold. Nerve cells also make the skin sensitive to pressure and touch. In addition, the skin contains a group of specialized nerve endings that stimulate the nerve and endocrine systems. This stimulation results in sexual excitement.
  
  
• Waste disposal. The skin is a minor source of waste disposal. Sweat glands located in the skin excrete waste products such as urea (a byproduct of protein metabolism) therefore eliminating them from the body.
  
  
• Indication of health problems. The skin’s characteristics (e.g., texture, temperature, color, clarity) provide information about a person’s general health and suggest a number of disorders. For instance, jaundice (a yellow color in the skin) may be a sign of liver disease or anemia (a condition characterized by too few red blood cells).