The skeletal system is constituted by bones, cartilages and ligaments. This system provides 'the shape' to the body. Further, bones remain as re-gions for the attachment of muscles. It also helps to hold weight. Structures like skull, protect inner organs. This system is also useful in locomotion. The bones remain as reservoirs of fat and certain minerals. The bone marrow is the site for the production of erythrocytes.
The bones can be long, short, flat or irregular in shape. Hands and legs have long bones. Short bones are broad in shape. Carpals (wrist bones) and tarsals (antkle bones) are shorter. Flat bones are thin and flattened. Skull bones, ribs, sternum and scapula (shoulder blade) are flat bones. Verterbral and facial bones are irregular in shape.
A bone is covered by a double layered sheath called the periosteum. The outer layer of the periosteum is fibrous in nature. It is a dense collag-enous layer having blood vessels and nerves.
A growing long bone has three regions. The long bony part is the dia-physis or shaft. It is made up of compact bone.
Axial skeleton - It forms the upright axis of the body. It protects the brain, the spinal cord and the vital organs found within the thorax.
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