A bone thickens by
A. Activity of osteocytes in the medullary cavity
B. increased secretion of calcium salts by osteoclasts
C. Adding blood vessels and nerves
D. None of the above
To determine the correct answer, we need to understand how bones thicken and what processes are involved.
Bones are dynamic tissues that undergo constant remodeling throughout life. They adapt to mechanical stress and repair themselves when damaged. The process by which bones thicken is called bone modeling and remodeling.
The bone remodeling process involves the activity of two main types of bone cells: osteoblasts and osteoclasts. Osteoblasts are responsible for bone formation, while osteoclasts are involved in bone resorption or breakdown.
When a bone needs to thicken or strengthen, the activity of osteoblasts is crucial. Osteoblasts produce new bone tissue, which is deposited on the existing bone surface. They secrete organic compounds, such as collagen, and mineralize them with calcium salts, like hydroxyapatite, to form new bone.
Based on this information, we can eliminate options B and C. Osteoclasts are responsible for the breakdown of old or damaged bone tissue, so they don't play a direct role in bone thickening. Similarly, adding blood vessels and nerves is not the primary mechanism by which bones thicken.
Now let's examine option A, which states that bone thickens due to the activity of osteocytes in the medullary cavity. Osteocytes are mature bone cells that are found within the bone matrix, and their primary function is to maintain bone tissue. While osteocytes sense and respond to mechanical stress, they are not directly responsible for bone thickening.
Therefore, the correct answer is D. None of the above. Bone thickening is primarily orchestrated by osteoblasts, which deposit new bone tissue on the existing bone surface.