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CHAPTER 3
Sensitivity of Various Organs of the Body
LEARNING OUTCOMES
At the end of the lesson, the student should be able to:-
• Explain factors which affect organ sensitivity.
• Explain cellular components
The Cell
• Three Main Parts: 1. Cell Membrane 2. Cytoplasm 3. Nucleus
• Cell Membrane – Protects the cell, holds water/nutrients and is
semipermeable.
• Cytoplasm – Composed mostly of water, Conducts cell metabolism, and
contains organelles.
Organelles 1. Centrosomes – Participate in cell division.
2. Ribosomes – Synthesize protein.
3. Lysosomes – Intracellular digestion.
4. Mitochondria – Produce energy.
5. Golgi Apparatus – Combines proteins & carbohydrates.
6. Endoplasmic Reticulum – Moves food/molecules in cell.
• Nucleus – Contains DNA and RNA – DNA controls cell function.
Law of Bergonie’ and Tribondeau
 It was developed in 1906 by two French
radiobiologist, Bergonie’ and Tribondeau
It offers a prediction about the relative
sensitivity of two different types of cells or
tissues to radiation
Law of Bergonie’ and Tribondeau
 It states that the radiosensitivity of cell is directly
proportional to their reproductive activity and
inversely proportional to their degree of
differentiation.
 Cells most active in reproducing themselves and cells
not fully mature will be most harmed by radiation.
 The more mature and specialized in performing
functions as cell is, the less sensitive it is to radiation.
More radiosensitive cells
Cells that have a high division rate
Cells that have a high metabolic rate
Cells that are of a non-specialized type
Cells that are well nourished
Sensitivity – Cell Cycle Phase
 Cells are most sensitive to
radiation during mitosis
(M phase) and RNA
synthesis (G2 phase)
 Less sensitive during the
preparatory period for
DNA synthesis (G1 phase)
 Least sensitive during
DNA synthesis (S phase)
 During mitosis (M), the
metaphase is the most
sensitive
Radioresistant cells
 Bone
 Liver
 Kidney
 Cartilage
 Muscle
 Nervous tissue
Radiosensitive cells
Germinal cells
Lymphoid tissues
 basal cells
Hematopoietic tissues
Epithelium of the GI tract
Gonads are very radiosensitive
Females
Temporally sterility 1.5 Gy (150 rad)
Permanent sterility 5 Gy (500 rad)
Males
Temporally sterility 2.5 Gy (250 rad)
Permanent sterility 6 Gy (600 rad)
Pregnancy and minors
Children could be expected to be more
radiosensitive than adults
fetuses more radiosensitive than children and
embryos even more in the first weeks of
pregnancy when organs are forming
Radiosensitivity of various cell types
Radiosensitivity
Low
Intermediate
High
Cell type
nerve cell
muscle cells
osteoblast,endothelial
cells,fibroblast,spermatids
spermatogonia,
lymphocytes, stem cells,
intestinal mucosa cells and
erythroblast
Questions
1. The law of Bergonie and tribondeau states that the
radiosensitivity of cell is directly proportional to
their reproductive activity and inversely
proportional to their degree of differentiation.
2. Those cells with a low metabolic rate are more
radiosensitive.
3. Cells are more sensitive during meiosis phase.
4. Gonads are very radiosensitive cells
5. List four of the radioresistant cells.
Answer
1.
2.
3.
4.
5.
True
False
False
True
bone, liver, kidneys, muscles