Bones advantages

Bones also protect the organs in our bodies. The skull protects the brain and forms the shape of the face. The spinal cord, a pathway for messages [blank] the brain and the body, is protected by the backbone or spinal column. The ribs form a cage that [blank] the heart and lungs, and pelvis help protect the bladder, part of the intestines, and in women, the reproductive organs. Bones are made up of a framework of a protein called collagen, with a mineral called calcium phosphate that makes the framework hard and strong. Bones store calcium and release some into the bloodstream when it's needed by other parts of the body. The amounts of certain vitamins and minerals that you eat, especially vitamin D and calcium, directly affect how much calcium is stored in the bones. Joints are where [blank] bones meet. They make the skeleton flexible -- without them, the movement would be impossible. Joints allow our bodies to move in many ways. Some joints open and close like a [blank] (such as knees and elbows), whereas others allow for more complicated movement -- a shoulder or hip joint, for example, allows for backward, forward, sideways, and rotating movement. Joints are classified by their range of movement: Immovable, or fibrous, joints don't move. The dome of the skull, for example, is [blank] of bony plates, which move slightly during birth and then fuse together as the skull finishes growing. Between the edges of these plates are links, or joints, of fibrous tissue. Fibrous joints also hold the teeth in the jawbone. Partially movable, or cartilaginous, joints move a little. They are linked by cartilage, as in the spine. Each of the vertebrae in the spine moves in relation to the one above and below it, and together these movements give the spine its flexibility. [blank] movable, or synovial (pronounced: sih-no-vee-ul), joints move in many directions. The main joints of the body -- such as those found at the hips, shoulders, elbows, knees, wrists, and ankles -- are freely movable. They are filled with synovial fluid, which acts as a lubricant to help the joints move easily. [blank] kinds of freely movable joints play a big part in voluntary movement: Hinge joints allow movement in one direction, as seen in the knees and elbows. Pivot joints allow a rotating or twisting motion, like that of the head moving from side to side. Ball-and-socket joints allow the greatest freedom of movement. The hips and shoulders have this type of joint, in [blank] the round end of a long bone fits into the hollow of another bone.