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Ninth lecture.

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Presentation on theme: "Ninth lecture."— Presentation transcript:

1 ninth lecture

2 Male reproductive system
In human male, stem cells and spermatogonia are highly sensitive. Spermatids and mature sperm show considerable resistance. Sterility is never seen immediately after radiation. Doses of about 6 Gy cause permanently sterilize males. Lower doses can also cause temporary sterility after several months. Fertility and near-normal sperm counts return after 1 to 2 years. 28

3 Female reproductive system
Radiation destroys both ova and maturing follicles. Radiogenic sterility in females is accompanied by artificial menopause. A dose of 2 Gy permanently sterilizes women over 40 but causes temporary sterility in women of age 35 or under. Menopause was caused in 50% of younger women exposed to doses of 1,5 to 5 Gy. Women over 40 showed 90% menopause at 1,5 Gy. 31

4 Skin Skin is relatively radiosensitive.
The response of the skin to ionizing radiation includes: 1. Initial erythema. 2. Dry desquamation. 3. Erythema proper. 4. Moist desquamation. 5. Necrosis. 6. Late effects 35

5 Mucous membranes Mucous membranes are also radiosensitive, particularly those in the mouth, pharynx, and esophagus. After considerable doses, dryness, soreness, and petechial ulceration of the mouth occur within 2 weeks. In the third week this progresses to swelling of the tongue with hypersecretion of the mucus, which eventually becomes a thick pseudomembrane that covers the buccal area, throat, and tongue. Later, fibrosis, ulceration, and poor vasculature accompanies skin effects. 41

6 The Fetus Fetal effects are seen at relatively low doses of radiation. The fetus is a highly proliferative system with many undifferentiated cells. Therefore it is extremely sensitive to radiation effects. The classic triad of effects of radiation upon the embryo are : 1. Intrauterine growth retardation (IUGR) 2. Embryonic, fetal, or neonatal death 3. Congenital malformation 44

7 Effects of radiation according to gestational stage
Preconception: No significant effects noted. Preimplantation: “All or none” Implantation: Transient Intrauterine growth retardation; threshold cGy. Organogenesis: Embryo sensitive to lethal, teratogenic and growth-retarding effects. IUGR, gross congenital malformations, microcephaly and mental retardation are the predominant effects for doses > 50 rads. 45

8 Specific radiation effects on the fetus
Mental retardation i-Highest risk during major neuronal migration (8-15 weeks). Incidence increases with dose. At 1 Gy (100 rads), 75% experience severe retardation ii-At weeks, fetus shows no increase in mental retardation at doses < 0.5 Gy (50 rads). IQ Risk factor associated with diminution of IQ is points at 1 Gy given in the gestational period 8-15 weeks. 47

9 Lens of the eye At doses 2-6 Gy damage the lens significantly to cause eventual cataract formation. There is no mechanism for removal of cells from the lens. Subsequently, radiation-damaged cells migrate to the posterior poles and centrally, as an opacity. Latent period is from 2-35 years, with a mean time of 8 years at single doses of Gy 49

10 Other Organs The viscera exhibits relative radioresistance.
The connective tissue and vasculature become the limiting structures, but functional damage can result from high doses. Lung: Radiation pneumonitis, an acute inflammatory reaction of the functional tissue and vasculature with doses of several thousands centigray after 4 to 6 months. Lung: Radiation fibrosis, accumulation of fibrin in alveoli and septa, 6 months to years after high doses. Blood vessels: Hemorrhage followed by progressive thickening and proliferation of endothelial cells. Kidney: Nephrosclerosis, nephritis, hypertension, and renal failure 2 to 3 years after doses of 30 Gy. 50

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