THE SKELETAL SYSTEM
The adult human body consists of approximately 206 bones. The variation in size and shape among the bones that make up the skeleton reflects their different roles in the body. Bones are made up of: 25% water, 30% organic material and 45% mineral.
The mineral matter consists mainly of calcium phosphate and a small amount of magnesium salts; this gives the bones its hardness.
The organic matter consists of fibrous material, which gives the bones its toughness and resilience.
The bones serve the following main functions:
• Provides a framework that supports the body; the muscles that are attached to the bones move the skeleton.
• Protects Some Internal Organs from mechanical injury; the rib cage protects the heart and lungs or skull around the brain for example.
• Contains and Protects the Red Bone Marrow, Haematopoiesis (Blood-forming) tissues (Red Blood Cells or Erythrocytes). Some White Blood Cells (Leukocytes) are also produced in Bones.
• Provides a storage site of inorganic salts, such as calcium. Calcium may be removed from bone to maintain a normal blood calcium level, which is essential for blood clotting and proper functioning of the muscles and nerves.
• Bones also provide a system of levers (rigid rods that can be moved about a fixed point) on which a group of specialized tissues (Muscles) act to produce motion.
There are 5 classifications for the bone:
1. Long bones. E.g. the femur or the thigh bone (these are the longest and strongest part of the body). Long bones consist of marrow surroundings.
2. Short bones. E.g. the metatarsal bones of the feet.
3. Flat bones. E.g. frontal bone of the head.
4. Irregular bones.
5. Sesamoid bones. E.g. Rounded masses found in certain tendons of the muscles being the patella or kneecap.
