An initial cartilaginous matrix is replaced during the process of endochondral o
ID: 101132 • Letter: A
Question
An initial cartilaginous matrix is replaced during the process of endochondral ossification by osteoblast cells a. True ??? Not 100% sure on this one b. False Parathyroid hormone (PTH) binds to receptors on osteoblasts a. True b. False Collagen in bone is a _____ a. lipid b. Carbohydrate c. Protein d. Fatty acid Cells that have only one nucleus and arc striated make up a. Smooth muscle (not striated) b. Skeletal muscle (multinucleated) c. Cardiac muscle If a thyroid tumor secreted an excessive amount of calcitonin in a teenager, we would expect a. An elevated level of osteoclast activity b. An elevated level of osteoblast activity c. A reduced rate of endochondral ossification d. A rise in blood calcium concentration e. Increasing bristle bones Increased amount of calcitonin would reduce the calcium concentration even more through an elevated level of osteoblast activity. Not sure if being a teenager changes the answer.. Blood Ca2+ deficiency stimulates _____ secretion, which leads to _____. Calcitonin, more urinary phosphate reabsorption b. Calcitriol. more urinary phosphate excretion c. Parathyroid hormone, increased osteoclast activity d. Growth hormone, increased osteoblast activity e. Thyroid hormone, less urinary calcium secretion _____ is synthesized by the combined action of the skin, UV, kidneys, and liver, and is important in the regulation of calcium levels in blood and bone. a. Growth hormone b. Testosterone c. Estrogen d. Calcitonin e. Calcitriol This image on the right shows the anatomy of a long bone. What does "4" represent? a. Marrow cavity b. Compact bone c. Spongy bone d. Epiphyseal line e. Articular cartilageExplanation / Answer
17. True, There are three types of cells involved in bone formation, growth and development. These cells are osteoblasts, osteocytes and osteoclasts. New bone formation starts with cartilage formation which is replaced later. During endochondral ossification osteoblasts penetrate into cartlage and replace it with spongy bone. Osteocytes represent mature bone and osteoclast is responsible for resorption of bone.
18. True, PTH involves in bone resorption which is a norma process performed by osteoclasts. But osteoclsts do not have its own resceptor for binding with PTH. PTH binds to osteoblast which indirectly affect the osteoclasts.
19. Option c is correct. Collagen is an insoluble fibrous protein.
20. Option c is correct. Cardiac muscles are mononucleated or binucleated and is striated also.
21. Option b is correct. Nothing to do with teenager. Although the status of bone formation and resorption is different in different age here the condition is thyroid tumor which will affect the level of calcitonin abnormally.
22. Option c is correct. Blood calcium dificiency stimulate PTH secretion which indirectly stimulate osteoclast activity and thus resorption process is increased and level of calcium is increased in blood.
23. Option e is correct. Calcitriol (1alpha,25(OH)2D3), the hormonally active form of vitamin D3 (D3) is produced by a series of reactions, including sun light activated D3 synthesis in the skin and subsequent hydroxylation at the C-25 atom in the liver and finally at C-1alpha position in the kidney.