Cellular sensitivities in approximate descending order from most to least sensitive are Lymphoid cells Germ cells Proliferating bone marrow cells Intestinal epithelial cells Epidermal stem cells Hepatic cells Epithelium of lung alveoli and biliary passages Kidney epithelial cells Endothelial cells (pleura and peritoneum) Connective tissue cells Bone cells Muscle, brain, and spinal cord cells The severity of radiation injury depends on the dose and the length of time over which it is delivered.