The Skeleton
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The Skeleton

The Skeleton of the Human Body

The skeleton gives the body its internal framework. Bone is a perfect construction material, combining great strength with light weight. Bones help to protect the body's soft organs. The dish-shaped hip bones enclose the intestines and bladder, while the ribs and backbone form a cage around the heart and lungs. These bones protect vital organs from everyday knocks and bumps.

An adult has 206 bones, although some people may have extra ribs or bones in their fingers. Of these, 26 bones make up the spine, each arm has 32 bones, and each leg 31. The largest bone are the femurs, or thighbones, which account for around a quarter of the skeleton's weight. The smallest bone, only 3 mm long, is the stirrup bone in the ear.Without bones we could not move, for it is the bones that muscles pull into place when we change position. Many bones have flat surfaces that provide an anchorage for large muscles. Some bones have projections from them, to which muscles are attached. One example is the shoulder blade, which provides anchorage for several muscles that work together to move the arm and shoulder.

Living bone contains large quantities of three important minerals:calcium, phosphorus, and potassium. These substances give bone its strength and hardness, but they are also needed in other vital processes such as sending messages along the nerves. If a person's diet does not contain enough of these minerals, the body ca use the supply of them that it has locked up in bones. This may weaken bones for a time until the supply can be replenished.Bone is alive, and continues to grow as the body matures. If a bone breaks it is able to mend itself by producing new cells. Bones cal also strengthen themselves, and so are able to stand up the the stresses and strain of a very active person. In a less active person they do not need to be strong, and the calcium that gives bone its hardness can be gradually dissolved away.

Not every bone can be shown in a diagram of a skeleton. For example, the ear bones that transmit sounds from the ear drum, and the hyoid bone supporting the tongue muscles in the throat are just too small. 

The 26 small bones that make up the spine are separated by cartilage disks. They are squashed by your weight as you walk, and can cause health problems.

The skull forms a hard case that protects the brain. A newborn baby has 29 separate bones forming its skull. These overlap when the baby is born, but gradually fuse firmly together during the firs two years of life. Only the lower jaw remains a separate, moving part, making it possible for food to be chewed.

The unique arrangement of bones in a human hand gives us the ability to touch the tip of each finger with our thumb. This means we can perform delicate tasks like threading a needle or coordinated activities such as holding a pen and unscrewing its top with just one hand. Other animals cannot do this.

Bones are not solid. Long bones like femur have a hard, strong outer layer of compact bone that surrounds lightweight spongy bone inside. A network of blood vessels and nerves runs in canals through these outer bone layers to the hollow center of bone marrow. The canals also carry lymph vessels. The type of bone marrow called red marrow produces millions of red blood cells every day. Most of our bones contain red marrow when we are children, but as we get older red marrow is to be found only in the skull, backbone, ribs, breastbone, hip and some limb stone.

Spot Facts

  • A Baby has about 350 individual bones, but an adult has only 206. As the skeleton grows, some of the smaller bones join to form larger ones.
  • Over 100 bones, or over half the bones in your body, are in your hands and feet.
  • Bones are one of the most durable parts of the human body. Human bones have been found that are well over 1 million years old.
  • The condition and position of skeletal remains can give vital clues as to how a person died.
  • Bones are incredibly resistant to bending forces. They can withstand stresses over 16,500 newtons per square centimeter.

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Comments (2)
Heather Ann Witt

Thanks this will be useful for science lessons

Ranked #7 in Science

The bones in the dominant arm of say, a professional tennis player can be about 1/3rd larger & more dense due to the requirement placed upon it...