ABSTRACT
This chapter discusses radiation damage or sparing of all kinds of body cells, tissues and organs in vivo, and with damage developing from radiation injury at any time after irradiation given in various modes, by any of the direct and/or indirect pathways. An understanding of the relative radiosensitivity of cells of different kinds, under different conditions, that is, both their essential and conditional radiosensitivity, is necessary to an adequate understanding of the complexities of radiation histopathology. The relationships between relative radiosensitivity and cell proliferation are complex. Radiation sensitivity and effects depend upon the phase of the cell-generation cycle, on the frequency of mitosis, and the length of the interphase. The relative sensitivity of a tissue is determined largely by: the relative radiosensitivity of its parenchymal cells; or in the case of a tissue containing series of developing cells, relative radiosensitivity of its radiosensitive cells. The endothelial tissue of the small blood vessels seems to be moderately sensitive to ionizing radiation.
