Bones and Joints: Quick Facts


The human skeleton is an engineering marvel with numerous functions: Not only does it give the body its needed support and a protective framework for vital internal organs, bit it also serves as a storehouse for calcium and other essential minerals and is critical in making new blood cells.

Although we tend to regard bones as being inert, in reality they are in a constant flux and also change dramatically over a lifetime. At birth, a baby has about 350 bones, a number of which are soft and pliable. As the child grows, the bones harden and many, such as those in the skill, fuse together.

The typical adult skeleton has 206 bones and weighs only about 20 pounds. Ounce for ounce, however, company bone tissue is one of nature's strongest materials. A cubic inch of bone can bear 19,000 pounds, making it four times stronger than reinforced concrete. Bones derive their incredible strength from their honeycombed structure and composition of calcium, phosphorous, and other mineral salts held together by collagen fibres. Nerves and blood vessels permeate the honeycombed structure and calcium and other minerals constantly move in and out of bone tissue. New blood cells are continually being made in the marrow, the spongy interior.

Red blood cells, platelets, and white blood cells are produced in the red marrow, which is found in flat bones such as the breast bone, skull, ribs, shoulder blades, and hip bones. Yellow marrow, which increases in quantity with age, produces white blood cells as well. Yellow marrow is composed of many fat cells, which is what gives it its yellowish color. Yellow marrow is found in the middle sections of long bones, such as the femur, humerus, radius, and ulnar. Bone marrow is also responsible for the production of stem cells.

Cartilage, a tough, slippery material, covers the ends of bones, cushioning the joints and reducing friction. Ligaments act as bindings to keep bones in place, and tendons attach muscles to the bones. To permit movement, bones at as levers, the joints are fulcrums, and muscles contract to provide the necessary force.

Age takes its toll on bones and joints. The knee and hips are especially vulnerable to degenerative arthritis. And with advancing age, bones begin to lose some of their calcium, making them porous and weak, a condition called osteoporosis.

Osteoporosis is a disease which affects many older women, but it can also affect men and young adults. It is a weakening of the bones, usually caused by poor nutrition and lack of weight bearing exercises (walking, running, weight lifting, etc.). Osteoporosis will be there to some extent with all older adults but the degree will depend on the above, and also proper nutrition and exercise during adolescence. Research has shown that building strong bones when young helps maintain bone density later on in life.

Best sources of calcium, which is vital for proper bone maintenance, include milk, cheese, green leafy vegetables, and if needed through vitamin supplements. Calcium is not stored in the body for very long so regular ingestion is important.

When a bone breaks it needs to be realigned to make sure it heals properly. If this is not done it may cause pain later on. Bones, compared to other connective tissue, heals quite quickly.

Note: Phosphorus is a chemical found in almost all soft drinks. There are some studies that indicate that this chemical causes calcium to be absorbed out of the bones leading to weaker bones.


There are several types of synovial joints:

  • Ball-and-socket: allow for all possible movement such as in shoulder and hip joints.
  • Hinge: allow for flexion and extension such as in elbow and knee.
  • Pivot: allow for rotation around an axis such as in twisting the wrist by using the radius and ulna.
  • Ellipsoidal: have a convex head in an elliptical concave socket such as in the wrist.
  • Saddle: such as the thumb.
  • Gliding: allow for a small amount of gliding back and forth such as in the vertebrae and the bones of the small wrist and foot.

Joints are held together by ligaments – strong connective fibrous tissue. They are also protected by synovial membrane which are filled by fluid.

Injuries to joints are usually serious, will take a very long time to heal and may never be as good as before. During such injuries it is very likely that the synovial capsule and ligaments have also been damaged. Complications arise because the joint needs immobilization to repair itself, but with immobilization joint becomes very stiff and a great deal of range of motion may be permanently lost. Therefore therapy is usually required during and after the healing process.

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