• The human skeletal system is comprised of about 206 separate bones plus associated cartilage, tendons and ligaments. This system takes up 20 percent of the body's total weight. Bones are formed from much softer cartilage as we mature from infants to adults. The skeletal system, a living organ, plays five major functions for humans.
  
  

Support

• The other 80 percent of our bodies is made up of soft tissue organs and muscles, all of which need to be supported. The skeletal system provides this support. In one fashion or another, through various connective tissues, all organs are attached either directly or indirectly to the skeletal system.
  
  The large bones of our lower bodies support the trunk when we stand. The skeletal system as a whole provides the necessary framework for humans to stand upright.
  
  

Protection

• Protecting those soft tissue organs is another major role for the human skeletal system. The brain is protected by fused bones that make up the skull, the spinal cord is surrounded by vertebrae that protect it and the rib cage provides protection to the heart, lungs and other nearby organs.
  
  

Movement

• The body is designed to move with a series of mechanical levers. Bones provide those levers and the joints between bones act as pivot points. As muscles contract and relax, the bones of the human skeletal system move allowing us to reach, walk, run, climb, sit, stoop and bend.
  
  

Red Blood Cells

• Known as hematopoiesis, bone marrow makes up most of the red blood cells required by the human body and some of the white blood cells as well. Marrow is a network of soft connective material that fills the cavities of bones.
  
  The process of hematopoiesis is carried on by the marrow in the skeletal system on a continuous basis depending on the needs of the body at any given time.
  
  

Mineral Storage

• The human skeletal system contains more calcium than any other organ in the entire body. Bones store calcium for times when blood calcium levels are increased or normal. They inject the blood with calcium during times when calcium levels are decreased. Like hematopoiesis, this is a continuous process.