Which of the following is considered to have the least sensitivity to radiation?

Muscle cells are considered to have the least sensitivity to radiation when compared to other cell types listed. This reduced sensitivity is primarily due to the nature and frequency of cell division. Muscle cells are generally more differentiated and have a lower rate of mitosis compared to other types of cells, such as epithelial cells or reproductive cells, which are constantly undergoing division and are thus more vulnerable to the effects of radiation.

Cells that divide more frequently, like epithelial and immature reproductive cells, are typically more affected by radiation exposure because radiation can disrupt the process of cell division, leading to mutations or cell death. Bone cells also have a notable regenerative aspect; however, they can still be more sensitive than muscle cells due to their involvement in constant remodeling and repair.

In summary, the relative stability and lower rate of division of muscle cells contribute to their decreased sensitivity to radiation, making them more resilient compared to other cell types that are more actively dividing.