The human body can be considered as a collection of interrelated parts or organs all made up of spe­cialised cells. It is possible to identify those organs which will be of most significance when considering radiation damage, usually because of the higher radio­sensitivity of rapidly dividing cells. It is worth con­sidering the general effect of radiation on a number of body components.

The Blood

The two main cellular components of blood are red cells and white cells. Red cells carry oxygen to and carbon dioxide from other cells in the body. They are produced from specialised parent cells in bone mar­row and, as they have no nucleus, are unable to re­plicate by division. There is a continuous renewal of red blood cells as they only have a lifetime of about four months.

White blood cells are of several types. They are produced in bone marrow, the spleen and lymph nodes and are concerned with fighting infection in the body.

A third type of cell, platelets, is concerned with the clotting of the blood.

The effect of a high radiation dose to the blood — forming organs is to induce cell death in the spe­cialised parent cells which prevents the formation of new blood cells. This has serious consequences, both for the transport of oxygen and carbon dioxide and for the body’s resistance to infection and its ability to heal wounds.