It is present in developing bones of the fetus and in some adult bones, such as the hip (pelvic) bones, ribs, sternum (breastbone), vertebrae (backbones), skull, and ends of the bones of the humerus (arm bone) and femur (thigh bone). Red bone marrow consists of developing blood cells, adipocytes, fibroblasts, and macrophages within a network of reticular fibers. Within certain bones, a connective tissue called red bone marrow produces red blood cells, white blood cells, and platelets, a process called hemopoiesis (hēm‐ō‐poy‐Ē‐sis hemo‐ = blood ‐poiesis = making). On demand, bone releases minerals into the blood to maintain critical mineral balances (homeostasis) and to distribute the minerals to other parts of the body.ĥ. Bone tissue stores about 99% of the body's calcium. Bone tissue stores several minerals, especially calcium and phosphorus, which contribute to the strength of bone. Mineral homeostasis (storage and release). This function is discussed in detail in Chapter 10.Ĥ. Most skeletal muscles attach to bones when they contract, they pull on bones to produce movement. For example, cranial bones protect the brain, vertebrae (backbones) protect the spinal cord, and the rib cage protects the heart and lungs.ģ. The skeleton protects the most important internal organs from injury. The skeleton serves as the structural framework for the body by supporting soft tissues and providing attachment points for the tendons of most skeletal muscles.Ģ. The skeletal system performs several basic functions:ġ. Also called mineralizationīone tissue makes up about 18% of the weight of the human body. Deposition of calcium salts, primarily hydroxyapatite, in a framework formed by collagen fibers in which the tissue hardens.
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