Old bones are dead, dry and brittle. But in the body, bones are very much alive. They have their own nerves and blood vessels, and they do various jobs, such as storing body minerals. A typical bone has an outer layer of hard or compact bone, which is very strong, dense and tough. Inside this is a layer of spongy bone, which is like honeycomb, lighter and slightly flexible. In the middle of some bones is jelly-like bone marrow, where new cells are constantly being produced for the blood.

Ball-and-Socket : The ball-shaped end of one bone fits into a cup shaped socket on the other bone allowing the widest range of motion including rotation. Examples include the shoulder and hip. Hinge: A convex projection on one bone fits into a concave depression in another permitting only flexion and extension as in the elbow and knee joints. Gliding: Flat or slightly flat surfaces move against each other allowing sliding or twisting without any circular movement. This happens in the carpals in the wrist and the tarsal in the ankle.

There are many ways that a ligament can help the body's bones move. With out a ligament your bodies bones would be unable to move. A ligaments attach bone to bone, stabilizing and strengthening joints and determining the range of motion. Cartilage plays a important role in the skeletal system. The cartilage is a gel- like substance which provides a protective cushioning..

Not long after a bone is broken it is replaced with a splint. The bone produces a material like substance that is in the gap of the break at each end of the bone. This helps hold them in alignment. The cartilage,ligaments,and tendons are replaced with a thick blood clot.

Here is a question that may stump you. How many bones are in the human body? When you were born you had over 300 bones. As you grew, some of these bones began to fuse together. The result? An adult has only 206 bones! Skull and upper jaw 21 bones 3 tiny bones in each ear Lower jaw (mandible) Front neck bone (hyoid) Backbone or spine (26 separate bones or vertebrae) Ribs (12 pairs - same number for men and women) Breastbone Each upper limb has 32 bones: 2 in shoulder, 3 in arm, 8 in wrist, 19 in hand and fingers. Each lower limb has 31 bones: 1 in hip (one side of pelvis), 4 in leg, 7 in ankle, 19 in foot and toes.