A&P chapter 6

Discuss the roles of osteoclasts and osteoblasts in bone remodeling processes of bone resorption and deposition.

. Remodeling is the ongoing replacement of old bone tissue by new bone tissue. 2. Old bone is constantly destroyed by osteoclasts, whereas new bone is constructed by osteoblasts. 3.

Decribe the role of remodeling in orthodontics.

. Remodeling is the ongoing replacement of old bone tissue by new bone tissue. Remodeling allows teeth to be moved during orthodontia.

Describe the process of growth in thickness. List and describe the function of the cells responsible for this process.

1. Bone can grow in thickness or diameter only by appositional growthat the periosteum 2. Bone grows in diameter as a result of interstitial and appositional addition of new bone tissue by osteoblasts around the outer surface of the bone and to a lesser extent internal bone dissolution by osteoclasts in the bone cavity.

describe the histology features and their functions found in compact bone tissue.

1. Compact Bone a. Compact bone is arranged in units called osteons or Haversian systems (Figure 6.3a) and is found on the outside of bones. b. Osteons contain blood vessels, lymphatic vessels, nerves, and osteocytes along with the calcified matrix. c. Osteons are aligned in the same direction along lines of stress. These lines can change as the stresses on the bone changes.

compare and contrast the two types of bone formation, noting the location where each kind of ossification occurs.

1. Intramembranous ossification is the formation of bone directly from or within fibrous connective tissue membranes. 2. Endochondral ossification is the formation of bone from hyaline cartilage models.

Describe the four types of cells in bone tissue and their function

1. Osteogenic cells undergo cell division and develop into osteoblasts. 2. Osteoblasts are bone-building cells, promoting bone deposition 3. Osteocytes are mature bone cells, derived from osteoblasts, that maintain bone tissue. 4. Osteoclasts are derived from monocytes and serve to break down, or resorb, bone tissue.

Describe the zones of the epiphyseal plate and the role of the epiphyseal plate in growth in the length of bones. List and describe the function of the cells responsible for this process.

1. To understand how a bone grows in length, one needs to know details of the epiphyseal or growth plate 2. The epiphyseal plate consists of four zones: the zone of resting cartilage, zone of proliferation cartilage, zone of hypertrophic cartilage, and zone of calcified cartilage (Figure 6.7). 3. The activity of the epiphyseal plate is the only means by which the diaphysis can increase in length. 4. When the epiphyseal plate closes, is replaced by bone, the epiphyseal line appears and indicates the bone has completed its growth in length.

Briefly describe some of the hormonal abnormalities that affect height.

2. The most important hormones for stimulation of bone growth during childhood are the insulinlike growth factors (IGFs), which are stimulated by human growth hormone (hGH). 3. Thyroid hormones and insulin are also necessary hormones for bone growth.

discuss the use of bone scans as a diagnostic procedure to indicate bone abnormalities

A bone scan is a diagnostic procedure that can detect certain bone abnormalities or disorders (Clinical Application).

Define a fracture and describe several common kinds of fractures.

A fracture is any break in a bone. 2. Common fractures include open (compound) fracture (Figure 6.8a), closed (simple) fracture, comminuted fracture (Figure 6.8b), greenstick fracture (Figure 6.8c), impacted fracture (Figure 6.8d), Pott's fracture (Figure 6.8e), and Colles's fracture (Figure 6.8f). 3. A stress fracture is a series of microscopic fissures in bone that forms without any evidence of injury to other tissues.

major tissue types associated with the skeletal system

A. Bone is made up of several different tissues working together: bone, cartilage, dense connective tissue, epithelium, various blood forming tissues, adipose tissue, and nervous tissue. B. Each individual bone is an organ; the bones, along with their cartilages, make up the skeletal system.

describe the distribution of blood and nerve supply in bones

A. Bone is richly supplied with blood (Figure 6.4). B. The arterial supply to bone involves several vessels. 1. The periosteal arteries pass through Volkmans' canals to a multitude of vessels that supply the outer compact bone region (Figure 6.4). 2. The nutrient artery passes through the nutrient canal and sends branches into the central Haversian canals to provide nutrients for osteocytes (Figure 6.4). 3. The artery continues into the medullae to supply blood for the marrow and osteocells via the epiphyseal artery. (Figure 6.4) C. Veins that carry blood away from long bones are evident in three places. (Figure 6.4) 1. One or two nutrient veins follow the nutrient artery in the diaphysis. 2. Epiphyseal and metaphyseal veins accompany epiphyseal and metaphyseal arteries in the epiphysis. 3. Periosteal veins exit with their periosteal arteries in the periosteum. D. Nerves follow vessels into bone tissue and the periosteum where they sense damage and transmit pain messages.

discuss functions of support, protection, assistance in movement, mineral homeostasis, blood cell production, and triglyceride storage.

A. Bones support the soft tissues and provide attachment sites for muscles, thereby serving as the structural framework for the body. B. Many of the body's internal organs are physically protected by bony coverings. C. Bones assist skeletal muscles to produce movement of body partst. D. Bones store and release several minerals, especially calcium and phosphorus, to help maintain mineral homeostasis. E. Hemopoiesis, blood cell formation, occurs in the red marrow of bones. F. Yellow marrow of adult bones serves as a site of triglyceride storage.

Contrast the courses and clinical symptoms associated with osteoporosis, rickets, and osteomalacia.

A. Osteoporosis is a decrease in the amount and strength of bone tissue owing to decreases in hormone output. In osteoporosis, bone resorption outpaces bone formation. B. Rickets and osteomalacia are disorders in which bones fail to calcify.

Describe the effects of mechanical stress, such as exercise, on bone maintenance and development.

A. Within limits, bone has the ability to alter its strength in response to mechanical stress by increasing deposition of mineral salts and production of collagen fibers. B. Removal of mechanical stress weakens bone through demineralization (loss of bone minerals) and collagen reduction. C. Weight-bearing activities, such as walking or moderate weightlifting, help build and retain bone mass.

Discuss the effects of aging on bone tissue, especially in regards to bone mass and strength.

A.Of two principal effects of aging on bone, the first is the loss of calcium and other minerals from bone matrix (demineralization), which may result in osteoporosis. B. The second principal effect of aging on the skeletal system is a decreased rate of protein synthesis, resulting in decreased production of matrix components (mostly collagen) and making bones more susceptible to fracture.

.Discuss the role of minerals, vitamins, and hormones in bone growth and remodeling.

Adequate dietary intake of minerals and vitamins is necessary for growth and maintenance of bone.a. Calcium and phosphorus are needed for bone growth in large concentrations, with other minerals needed in smaller amounts.b. Vitamins C, K, B12, and A are needed for bone growth.

Compare and contrast the role of hormones (PTH and CT) that stimulate opposing activities of bone cells, in order to maintain blood calcium homeostasis.

An important hormone regulating Ca2+ exchange between bone and blood is parathyroid hormone (PTH), secreted by the parathyroid gland. It increases blood calcium ion levels (Figure 6.10). Another hormone that contributes to the homeostasis of blood Ca2+ is calcitonin (CT). It is secreted by the thyroid gland and decreases blood Ca2+ levels.

list and describe parts of the long bone

B. A typical long bone consists of numerous parts.1. The diaphysis is the shaft of the long bone. 2. The epiphyses are the ends of the bone, that articulate with adjacent bones. 3. The metaphyses are the areas between the epiphysis and diaphysis. It includes the epiphyseal plate, which the site of bone elongation, in growing bones. 4. Hyaline cartilage (articular cartilage) at the ends of the bones reduces friction and absorbs shock at freely moveable joints. 5. The periosteum is a connective tissue covering of the surface of the bone which contains osteogenic cells which promotes bone growth in width, assists in fracture repair, helps nourish bone tissue, and serves as an attachment point for ligaments and tendons. 6. The space within the diaphysis is the marrow cavity which contains yellow marror, or adipose connective tissue 7. The endosteum is the lining of the medullary cavity.

describe the steps involved to intramembranous ossification.

B. Intramembranous ossification forms the flat bones of the skull and the mandible (Figure 6.5). 1. An ossification forms from mesenchymal cells as they convert to osteoblasts and lay down osteoid matrix. 2. The matrix surrounds the cell and then calcifies as the osteoblast becomes an osteocyte. 3. The calcifying matrix centers join to form bridges of trabeculae that constitute spongy bone with red marrow between. 4. The periosteum first forms a collar of spongy bone that is then replaced by compact bone.

describe the steps involved in endochondral ossification.

C. Endochondral ossification involves replacement of cartilage by bone and forms most of the bones of the body (Figure 6.6). 1. The first step in endochondral ossification is the development of the cartilage model. 2. Step two is the growth of the cartilage model. 3. In step three, the primary ossification center develops in the diaphysis. Cartilage is being removed and replaced by bone 4. Step four results in the formation of a medulary cavity 5. Step five involves the development of secondary ossification centers in the epiphysis. 6. The final process is the formation of articular cartilage and the epiphyseal plate.

List and describe the steps involved in fracture repair.

Fracture repair (Figure 6.9)involves formation of a clot called a fracture hematoma, organization of the fracture hematoma into granulation tissue called a procallus (subsequently transformed into afibrocartilaginous [soft] callus), conversion of the fibrocartilaginous callus into the spongy bone of a bony (hard) callus, and, finally, remodeling of the callus to nearly original form.

contrast and compare the structure and composition of spongy bone versus compact bone

Spongy (cancellous) bone does not contain osteons but, instead, consists of trabeculae surrounding many red marrow filled spaces (Figure 6.3b). It forms most of the interior structure of short, flat, and irregular bones, and the epiphyses of long bones. c. Spongy bone tissue is light and provides open spaces for the red bone marrow and, as such, is the site of hemopoesis..

describe the chemical components of bone

The matrix of bone contains inorganic salts, primarily hydroxyapatite and some calcium carbonate, and collagen fibers .1. These and a few other salts are deposited in a framework of collagen fibers, a process called calcification or mineralization. 2. Mineral salts confer hardness on bone while collagen fibers give bone its great tensile strength. 3. The process of calcification occurs only in the presence of collagen fibers.

Discuss some treatments for fracture.

Treatments for fractures include the anatomic realignment of the bone fragments, immobilization to maintain realignment, and restoration of function.

role of osteology in understanding bone structure and disorders

support the soft tissues and provide attachment sites for muscles, thereby serving as the structural framework for the body. B. Many of the body's internal organs are physically protected by bony coverings. C. Bones assist skeletal muscles to produce movement of body partst. D. Bones store and release several minerals, especially calcium and phosphorus, to help maintain mineral homeostasis. E. Hemopoiesis, blood cell formation, occurs in the red marrow of bones. F. Yellow marrow of adult bones serves as a site of triglyceride storage.