Anatomy Chapter 5- Osseous Tissue and Skeletal Structure

4. List and briefly describe 4 types of cells in mature bone.

1. Osteocytes- Mature Bone cells, Maintain the protein and mineral content of the matrix. Each osteocyte directs both the release of calcium from the bone to blood and deposition of calcium salts in the surround matrix. Osteocytes occupy small chambers called lacunae which are sandwhiched between maxtrix layers known as lamellae. Channels called canaliculi, extend from the osteocytes to bone capillaries. 2. Osteoblasts- Cells that are cubodial in shape and are found in a single layer on the inner or outer surfaces of a bone. Immature bone cells. Found on the inner and outer surface of bones. These cells secret the organic components of the bone matrix. This material is called osteoid, which is later mineralized through complicated, multistep mechansim. Osteoblasts are responsible for the production of new bone which is called osteogenesis. 3. Osteoprogenitor cells- Bone tissue also contains small numbers of flattened or squamous shaped stem cells termed osteoprogenitor cells. These are bone stem cells. These cells are found on the innermost layer of the periosteum and inner lining of the endostum. Differentiate to form new osteoblasts. Heavily involved in the repair of bones after a break. 4. Osteoclasts- Miltinucleated cells. Found at the sites where bone is being removed. Secrete acids, which dissolve the bones thereby causing the release of stored calcium ions and phosphate ions into the blood. The erosion process is called osteolysis.

List the 4 major components to the skeletal system.

1. Skeletal Bones 2. Cartilage 3. Ligaments 4. Connective Tissue

List the major components of osseous tissue.

1. Specialized Cells- These include the osteoblasts, osteocytes, osteoprogenitor cells, osteoclasts 2. Solid Matrix- Calcium phosphate make up 2/3 of the bone mass. This calcium phosphate interacts with calcium hydroxide to form crystals of hydroxyapatite. As the Hydroxyapatite form, they also incorporate other calcium salts such as calcium carbonate, and ions such as sodium, magnesium, and fluoride. These inorganic components enable bone to resist compression. Collagen Fibers make up 1/3 of the bone matrix. Collagen and hydroxyapatite make bone tissue extremely strong. Bone cells contribute only 2 percent of the bone mass. 3. Periosteum- Out surface of a bone is covered by periosteum. Periosteum isolates and protects the bone from surrounding tissues, provides a route and a place of attachment for circulatory and nervous supply, and attaches the bone to the connective tissue network of the deep fascia. 4. Endosteum- Inside the bone, a cellular endosteum line the medullary cavity. This layer covers the trabeculae of spongy bone and lines the inner surfaces of the central conals and perforating canals.

List and briefly describe 5 major functions of the skeletal system.

1. Support- The skeletal system provides support for the entire body. Individual bones or groups of bones provide a framework for the attachment of soft tissues and organs 2. Storage of Minerals- Calcium salts of the bone act as as valuable mineral reserve of calcium and phosphate. Ton of calcium is stored in the bone and calcium is also the most abundant mineral in the body. 3. Blood Cell Production- The red marrow filled in the internal cavity of bones; helps produce red blood cells, white blood cells, and platelets. 4. Protection- Delicate tissues and organs are often surrounded by skeletal element. Example would be the ribs protecting the heart. 5. Leverage- Many bones in the body function as levers. They can change the magnitude and direction of the forces generated by skeletal muscles.

5. What is the basic unit of skeletal bones called and what are some of its major features? Label Figure 5.2 (b,c) with these structures.

Cylindrical Osteon. Central Canal- Contains the blood vessels that supply the osteon. These canals run parallel to the surface of the bone. Perforating Canal- extend roughly perpendicular to the surface. Blood vessels in the perforating canals deliver blood to osteons deeper in the bone and service the medulalry cavity. Concentric Lamellae- cylindricl and aligned parallel to the long axis of the bone. Collectively, these concentric lamellae form a series of concentric rings, resembling a "bull's-eye" target., around the central canal. Interstitial lamellae- fill in the spaces between the osteons in compact bone. Circumferential lamellae- Occurs at the external and internal surfaces of the bone. In a bone such as the humerus or femur, the circumferential lamellae form the outer and inner surfaces of the shaft. Trabeculae-