Biology 252 Exam 2 Questions And Answers Solved 100% Correct!!

Describe the cells of the bone tissue - Answer--Osteogenic cells -Osteoblasts -Osteocytes -Osteoclasts What membrane lines the internal canals and the small cavities of the compact and spongy bones? - Answer-Endosteum What is the periosteum composed of? - Answer--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 - Answer--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 - Answer--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? - Answer-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 bonematrix is dense and 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. - Answer-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? - Answer-Since we need calcium for everything, the parathyroid hormone stimulates osteoclast activity and breaks down bones to release calcium. Bones become brittle and porous. The epiphyseal cartilage becomes ossified in our youth. On the other hand, the articular cartilage does not become ossified. Why is that advantageous? - Answer-Growth of articular cartilage results in an increase in the size of the epiphyses. This is only one of the functions of articular cartilage; it also forms a smooth, resilient covering over the ends of the epiphyses within joints. Ossified articular cartilage could not perform that function. A 12 year old girl produces relatively large amount of estrogen, a sex hormone that stimulates growth of the epiphyseal plate, as well as the rate of ossification. How will that affect her height in future months? At the age of 25? - Answer-Her growth for the next few months increases, and she may be taller than a typical 12-year-old female. Because the epiphyseal plates ossify earlier than normal, however, her height at age 18 will be less than otherwise expected. Why do astronauts experience a dramatic decrease in bone density? - Answer-When a limb is immobilized in a cast, when an astronaut experiences zero gravity, or whenever a person lies down, the weight-bearing bones of the body such as those in the spine and leg, are relieved of their burden, a condition known as skeletal unloading.When skeletal unloading persists for several weeks, bones start to deteriorate: the number of bone cells decreases, movement into the bone of such minerals as calcium and phosphorous slows, and production of bone-cell precursors called osteoprogenitor cells diminishes. All these changes result in weakened, brittle bones prone to fracture. ` In Rickets the long bones become abnormally long. Why? - Answer-Epiphyseal plates cannot be calcified, therefore they continue to widen and causes the ends of long bones to become abnormally long and enlarged Which of the following is correct? - Answer-a. Calcified cartilage is the major component of the bone tissue b. The chondrocyets are responsible for calcification of the cartilage matrix c. The epiphyseal plate marks the primary ossification center d. During bone growth the diaphysis does not grow in length