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BIOLOGICAL EFFECTS OF IONIZING RADIATION ON TISSUES, ORGANS AND SYSTEMS.

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Presentation on theme: "BIOLOGICAL EFFECTS OF IONIZING RADIATION ON TISSUES, ORGANS AND SYSTEMS."— Presentation transcript:

1 BIOLOGICAL EFFECTS OF IONIZING RADIATION ON TISSUES, ORGANS AND SYSTEMS

2 Types of cellular damage Interphase cell death Changes of metabolism & function Mitotic cell death Norma repair Mutation

3 Moderately radiosensitive Skin Vascular endothelium Lung Kidney Liver Lens (eye) Radiosensitivity of tissues Highly radiosensitive Lymphoid tissue Bone marrow Gastrointestinal epithelium Gonads Embryonic tissues Bone marrow Skin CNS Least radiosensitive Central nervous system (CNS) Muscle Bone and cartilage Connective tissue

4 Relative radiosensitivity of various organs based on parenchymal hypoplasia OrgansRelative radio sensitivity Chief mechanism of parenchymal hypoplasia Lymphoid organs; bone marrow, testes & ovaries; small intestines Embryonic tissue High Destruction of parenchymal cells, especially the vegetative or differentiating cells Skin; cornea & lens of eyes; gastrointestinal organs: cavity, esophagus, stomach, rectum Fairly high Destruction of vegetable and differentiating cells of the stratified epithelium Growing cartilage; the vasculature; growing bones Medium Destruction of proliferating chondroblasts or osteoblasts; damage to the endothelium; destruction of connective tissue cells & chondroblasts or osteoblasts Mature cartilage or bone; lungs; kidneys; liver; pancreas; adrenal gland; pituitary gland Fairly low Hypoplasia secondary damage to the fine vasculature and connective tissue elements Muscle; brain; spinal cord Low Hypoplasia secondary damage to the fine vasculature and connective tissue elements, with little contribution by the direct effects on parenchymal tissues

5 Haematopoietic system Bone marrow

6 red blood cell platelets monocytes neutrophils basophils eosinophils B lymphocytes T lymphocytes Blood Bone marrow Proliferation Differentiation Thymus CFU-E CFU-MK CFU-M CFU-G CFU-Ba CFU-Eo CFU-BL CFU-TL Stem cell CFU-L CFU-GEMM BFU-E BFU-MK CFU-GM Hierarchical organization of haematopoiesis

7 Bone marrow kinetics Resting stem cells Proliferating compartment: stem cell and progenitors Differentiating compartment: precursors Mature cells Blood Normal physiological situation activation proliferation, differentiation exit Stem cells: immature cells with autorenewal capability Progenitors: primitive cells, high proliferative potential Mature cells: no proliferative capability

8 Effects of radiation on haematopoiesis Resting stem cells Proliferating compartment: stem cell and progenitors Differentiating compartment: precursors Mature cells Blood activation proliferation, differentiation Block of proliferation, cell death Depletion of proliferating compartment Depletion by absence of renewal BLOOD APLASIA IRRADIATIONIRRADIATION

9 Irradiated bone marrow lacks all precursor haematopoietic cells Normal bone marrow Effect of radiation on bone marrow

10 Model of blood renewal system Cell pools in normal steady state Stem cell Dividing & maturing Maturing only Blood ? 2 days 1 day Transit time Changes after irradiation Time After Irradiation 1 hour 1 day 2 days 3 days 4 1 / 4 days 5 days Relative Number of Cells

11 Erythrocytes changes as a function of dose 1 Gy 3 Gy

12 changes as a function of dose Leukocytes changes as a function of dose Normal <1Gy 1-2 Gy 2-5 Gy >5-6 Gy Neutrophils, per cent of normal Time after exposure, days

13 Thrombocytes changes as a function of dose Normal <1Gy 1-2 Gy2-5 Gy >5-6 Gy Platelets, per cent of normal Time after exposure, days

14 Normal monkey lymph node Germinal centre of normal monkey lymph node Germinal centre of irradiated human lymph node Lymphoid cells depleted in cortex of canine lymph node Effects of radiation on lymphatic tissue A B C D

15 Early changes in peripheral blood lymphocyte counts Gy Gy 2-4 Gy 4-6 Gy >6 Gy

16 Lymphocytes changes as a function of dose <1 Gy 1-2 Gy 2-5 Gy >5-6 Gy Time after exposure, days Lymphocytes, per cent of normal

17 Effect of radiation on gastrointestinal tract Irradiated gastrointestinal mucosa

18 Pathogenesis of the gastrointestinal syndrome  Depletion of the epithelial cells lining lumen of gastrointestinal tract  Intestinal bacteria gain free access to body  Haemorrhage through denuded areas  Loss of absorptive capacity

19 Reproductive cell kinetics and sterility – male

20 Reproductive cell kinetics and sterility – female

21 Human skin structure

22 Penetration of radiation through skin stuctures Alpha radiation is absorbed in superficial layers of dead cells within the stratum corneum Beta radiation damages epithelial basal stratum. High energy ß- radiation may affect vascular layer of derma, with lesion like thermal burn Gamma radiation damages underlying tissues and organs

23 Normal Irradiated Effect of radiation on skin

24 Pulmonary effects Irradiated lung tissue Pulmonary fibrosis

25 Summary of lecture  Bone marrow consists of progenitor and stem cells, the most radiosensitive cells in the human body and the most important in controlling infection   Doses in tens of gray produce central nervous system syndrome, causing death before appearance of the haematopoietic or gastrointestinal syndromes   The latter syndromes may occur after doses of as low as 2.5 and 8 Gy, respectively. Lesions in the brain are usually caused by damage to the vascular endothelium   Lung lesions do not usually appear at radiation doses less than 10 Gy. Significant concern in partial-body irradiation and in radiation therapy

26 Lecture is ended THANKS FOR ATTENTION In lecture materials of the International Atomic Energy Agency (IAEA), kindly given by doctor Elena Buglova, were used


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