Chapter 5: the Skeletal System

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Chapter 5: The Skeletal System

I.Introduction. The skeletal system consists of the bones, along with the cartilage and fibrous connective tissue that make up the ligaments that connect bones to bone at joints. A.Functions of the Skeleton.

1.The skeleton supports the body.
2.The skeleton protect soft body parts.
The skull protects the brain, the rib cage protects the heart and lungs, and the vertebrae protect the spinal cord. 3.The skeleton produces blood cells. Red bone marrow contains stem cells that produce all of the blood cells. 4.The skeleton stores mineral and fat. All bones have a matrix that contains calcium phosphate that serves as a source of calcium and phosphate ions for the blood. Fat is stored in the yellow bone marrow. 5.The skeleton, along with the muscles, permits flexible body movement. B.Anatomy of a Long Bone. The shaft, or the main portion of the bone, is called the diaphysis. The diaphysis has a large medullary cavity, whose walls are composed of compact bone. The medullary cavity is lined with a thin membrane called the endosteum and is filled with yellow bone marrow. The enlarged ends of a long bone are called the epiphyses. The epiphyses are composed largely of spongy bone that contains the red bone marrow. The epiphyses are covered by a thin layer of hyaline cartilage in the joints. Areas of the bone other than at the joints are covered with a layer of fibrous connective tissue called the periosteum.

II.Bone Growth, Remodeling and Repair. Most bones grow in length and width occurs through adolescence, but some continue to enlarge until about age 25. In a sense, bones can grow throughout a lifetime because they are able to respond to stress by changing size, shape and strength. Bones are composed of living tissue, as demonstrated by their ability to grow, remodel and undergo repair. Several types of cells are involved in these activities. Osteoblasts are bone-forming cells. They secrete the organic matrix of the...
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