ninth lecture Male reproductive system In human male

ninth lecture

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.

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.

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

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.

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

Effects of radiation according to gestational stage • Preconception: No significant effects noted. • Preimplantation: “All or none” • Implantation: Transient Intrauterine growth retardation; threshold 10 -20 c. Gy. • 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.

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 16 -25 weeks, fetus shows no increase in mental retardation at doses < 0. 5 Gy (50 rads). • IQ Risk factor associated with diminution of IQ is 21 -33 points at 1 Gy given in the gestational period 8 -15 weeks.

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, radiationdamaged 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 2. 5 -6. 5 Gy

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.