Question

which one of the following is true?
a osteoblasts are large, multinucleated cells that break down calcified bone matrix.
b osteoclasts secrete bone matrix and become osteoblasts.
c osteoblasts deposit bone matrix around themselves and become osteocytes when they are isolated in lacunae.
d osteoclasts deposit bone matrix around themselves and become osteocytes when they are isolated in lacunae.

Explanation:

• Option A: Osteoclasts (not osteoblasts) are large, multinucleated cells that break down calcified bone matrix. So this option is incorrect.
• Option B: Osteoblasts secrete bone matrix. Osteoclasts are involved in bone resorption (breaking - down), not secretion to become osteoblasts. So this option is incorrect.
• Option C: Osteoblasts deposit bone matrix around themselves. As they become surrounded by the matrix, they differentiate into osteocytes (mature bone cells) and are isolated in lacunae. This is correct.
• Option D: Osteoclasts do not deposit bone matrix. Osteoblasts are the matrix - depositing cells. So this option is incorrect.

Answer:

C. Osteoblasts deposit bone matrix around themselves and become osteocytes when they are isolated in lacunae.