anim_bone_dynamics_tissue_answer_key.doc

Bone Dynamics and Tissue To complete this worksheet, select: Module: Support and Movement Activity: Animations Title: Bone Dynamics and Tissue Introduction 1. Why is bone tissue called dynamic? It is dynamic because it cycles through, being reduced to its primary components to be reabsorbed into the body and then built up again from these components. This homeostatic process is regulated by the body’s requirements at any given moment. 2. Describe the process and timing of bone remodeling. Bone remodeling starts by having its bone cells (osteoclasts) resorb its own tissue thereby releasing calcium & other minerals for use throughout the body. When restoring bone tissue, bone cells form new bone, taking minerals from the bloodstream and storing it in the bone matrix. 3. How does remodeling change bone structure in response to slight and heavy stress? Remodeling of bone tissue is dependent upon the demands placed upon it. If an individual leads a sedentary and relaxed lifestyle, bone tissue is reduced and excessive bone matrix is resorbed into the body. In contrast, if an individual leads a physically demanding schedule like that of a professional athlete, then bone mass is increased to handle the additional mechanical stresses. 4. a. Describe the composition of bone matrix. Include the importance of collagen fibers and inorganic mineral salts such a calcium phosphate (also known as hydroxyapatite). Bone matrix is connective tissue that is both dense and resilient. Embedded collagen fibers provide for its resilience while calcium phosphate is responsible for the density and firmness in bone. b. Bone composition gives it great tensile strength. What does this mean? The combination of both these fibers with the minerals salts furnishes bone its capacity to withstand pressure along its long axis. 5. a. Describe the role of the following cells and structures: Mesenchymal cells primordial cells from which all connective tissue arise. Osteogenic cells are stem cells of bone derived from mesenchyme and undergo cell division which gives rise to osteoblasts. Osteoblasts are cells that synthesize & secrete osteoid (collagen fibers & other organic material) and begin the calcification of matrix. Lacunae spaces in which osteoblasts are trapped in after calcification has begun. Osteocytes mature bone cells that are derived from osteoblasts. These are the main cells in bone tissue that maintain its daily metabolism. Osteoclasts large, multinucleated cells formed from the fusion of monocytes that are responsible for bone resorption. b. Explain how bone tissue matrix serves as a storage site for calcium and phosphate ions. Osteoclasts break down the bony matrix, and release phosphate and calcium into the blood when they are their blood concentrations are low. Conversely, osteocytes are stimulated to remove calcium and phosphate from the blood when their concentrations are high and sequester them in new bone matrix. This process of resorption (withdrawal) as well as their absorption (deposit) indicates the bone matrix as the body’s bank for calcium & phosphate. 6. What bones contain spongy and compact bone tissue? All the bones of the body contain both spongy and compact bone tissue. 7. a. Describe the following structural features of compact bone tissue. Osteons (Haversian systems) a basic unit of structure in adult compact bone. These structures are aligned in the same direction along lines of stress. Lamellae are plates of bone matrix . They are ring shaped in an osteon and longitudinally arranged near the periosteum. Where is compact bone located? These are found in the external portion of all bones and the majority (diaphysis) of the shafts of all long bones. It is also seen immediately deep to the periosteum and external to spongy bone. 8. a. Describe the following structural features of spongy, or cancellous, bone tissue. Lamellar arrangement spongy bone lamellae consists of trabeculae. These units are aligned in a delicate, lacy framework providing space for red bone marrow. Define trabeculae The structural unit of spongy bone. Its appearance gives spongy bone its name because its arrangement is that of an irregular lattice of thin columns. b. What fills the spaces between the trabeculae? Red bone morrow fills the space between the trabeculae. c. Where is spongy bone located and what is its function? Spongy bone tissue is found in short, flat, and irregularly shape bones. It also forms most of the ends of long bones (epiphysis.) It is also found in a narrow border around the medullary cavity of the diaphysis of long bones.