The skeletal system is made up of more than 280 bones. The bones act as a framework for the body giving it struc-ture and support . Bones also protect several internal organs. The bones of the skull joined toghether during the first year of life totally surround the brain. The vertebral column or spinal column protects the spinal cord. The rib cage guards the heart lungs and major blood vessels. Bones are the pas-sive organs of motion. The do not move by themselves. They must be moved by muscles which shorten or contract. This is an example of how systems work together. Bones also store minerals that are necessary for many other body activities and are involved in the constant reproduction of blood cells. Broken or fractured bones usually can mend solidly but the process is slow and gradual. Nones cells grow and reproduce slowly compared to other types of cells. The hardening of the new none is a gradual process of depositing cailcium . As we age our bones become more brittle
đang được dịch, vui lòng đợi..
