Biology 252 Exam 2| 121 Questions and Answers(A+ Solution guide)

Describe the cells of the bone tissue - -Osteogenic cells -Osteoblasts -Osteocytes -Osteoclasts What membrane lines the internal canals and the small cavities of the compact and spongy bones? - Endosteum What is the periosteum composed of? - -Dense irregular connective tissue -Collagen fibers -Outer fibrous layer has fibroblasts -Inner layer has progenitor cells that become osteoblasts Describe the matrix of the bone tissue - -Stony matter surrounding osteocytes and lacunae -1/3 organic (collagen and protein-carb complex) and 2/3 inorganic (CaK, CaCO3...) -gives bone flexibility and strength -Minerals resist compression -Collagen resists tension Compare the function of the organic and the inorganic material in the bone matrix - -Inorganic (minerals) resist compression -Organic (protein-carb complex/collagen) resists tension Why does calcification result in death of chondrocytes, while ossification does not result in death of osteocytes? - Chondroblasts are surrounded by cartilage matrix and receive oxygen and nutrients by diffusion through the matrix. When the matrix becomes calcified, diffusion is reduced the the point that the cells die. When osteoblasts form bone matrix, they connect to one another by their cell processes. Thus, when the matrix is laid down, canaliculi are formed. Even though the ossified bone matrix is denseand prevents significant diffusion, the osteocytes can receive gases and nutrients through the canaliculi or by movement form one osteocyte to another. Describe the process of endochondral ossification. - 1. Hyaline cartilage is covered with fibrous perichondrium 2. In middle of cartilage (primary oss. center), chondrocytes die, and the thin wall calcify. Perichondrium cells become osteoblasts and form bony collar-periosteum. 3. Blood vessels grow into primary oss. center. Osteoclasts come and hollow out calcified center (primary marrow cavity). Osteoblasts come and deposit bone, thickening shaft. Second oss. center develops at ends of bone. 4. Second oss. center hollows out secondary marrow cavity. Dividing line is formed-metaphysis. 5. Epiphyseal plate surrounding by metaphysis exists; enables bones to grow in length and width. 6. No more cartilage=no more room to grow; only cartilage is articular cartilage, which needs to stay mushy What is the effect of inadequate levels of calcium in the diet of an adult on the skeleton? - Since we need calcium for everything, the parathyroid hormone stimulates osteoclast activity and breaks down bones to release calcium. Bones become brittle and porous