Posted by DAM on February 3, 2012 in IONISING RADIATIONS | Short Link
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Following a substantial dose of radiation, there is a latent interval of hours or days before histological evidence of tissue injury is seen. As already explained, the damage depends on:

a- The dose

b- Type of radiation

c- The interval following exposure

d- The tissue exposed.


A) Early changes in the skin include:

  1. Dilatation of blood vessels, congestion of dermal vessels and other signs of acute inflammation and these reflect acute tissue injury.
  2. With a single dose, the mitotic activity of the basal cells is arrested with subsequent loss of the epidermis and epilation (loss of hair).
  1. The walls of the dermal vessels are infiltrated with fibrin.

    B- Late changes: The dermal vessels show the picture of endarteritis obliterans followed by replacement with hyaline collagen and this will hinder regeneration of epidermis.

    2- With repreated exposure to radiation; large bizarre fibrocytes are present in the dermal connective tissue, the dermal collagen becomes very dense and there is a tendency to become necrotic even years after exposure.

    3- Persistent melanin pigmentation is noted.

    Lymphoid and hemopoeitic tissue (are very sensitive to radiation).

    Necrosis of lymphoid and hemopoeitic tissue is manifested by changes in the peripheral blood cells which appear at different times depending on the length of life of different cells.

    1. The lymphocytes: are easily degenerated and necrosed with marked decrease in their number in the peripheral blood.
    2. The granulocytes: many show an initial rise followed by marked drop by the end of the second to the fourth weeks. This leads to diminished resistance with subsequent infection.
    3. The platelets: show an initial rise followed within few days by marked drop leading to haemorrhagic tendency.
    4. The red blood cells: are lately dcreased and anemia shows up after several weeks (6 weeks) due to their relative long life span.
    5. Leukemia may develop after many years from exposure to ionizing radiation due to mutation in lymphoid tissue.

    Intestinal Epithelium

    Degeneration and necrosis occur after two days and are accompanied by severe diarrhea. Disturbances in fluid and elecholyte balance may cause death.

    Healing of intestinal lesions may be followed by stensosis.


    Grauulosa cells are affected than the ovum so Graffian follicles appear small, and anovular.


    1-    Destruction of spermatogonia prevents further
    production of spermatorytes and spermatozoa.

    2-    Interstitial cells are not affected.
    Blood vessels

    1. Degeneration and necrosis of endothelium followed by acute inflammation of the wall and thrombosis.
  2. Healing is followed by vascular occlusion.

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