Effects Of Radiation Exposure On Human Cells Flashcards
Identify effects of radiation exposure on human cells
- early effects
- Late effects
- Somatic effects
- Genetic effects
- Effects on blood cells
- Effects on tissues
- Effects on reproductive cells
early effects
- Early deterministic somatic effects depend on the time of exposure
to ionizing radiation. - They appear within minutes; hours; days; weeks.
- A significant dose of radiation is necessary to induce biological changes shortly after exposure.
- The severity of these dose related early effects are precipitated by
cell death
possible high dose consequences of late effects
*fatigue
* erythema
(diffuse redness over an area of skin after irradiation)
* epilation,
* blood disorders
* intestinal disorders
* fever
* Dry and moist desquamation (shedding of the outer layer of skin)
* depressed sperm count in males and temporary or permanent infertility in the male.
and females
what name is given to deterministic effects.
- Acute radiation syndrome.(ARS)
Under what conditions does ARS occur in humans.
*ARS, or radiation sickness, occurs in humans after the whole body receives large doses of ionizing radiation over a short period.
e.g Atomic bomb survivors of Hiroshima and Nagasaki during WW2;
Late effects
- Effects appear months or years after
exposure to irradiation. - Radiation induced at cellular level may lead to measurable somatic and hereditary damage.
late effects may result from
- Previous whole-or partial body acute exposure
- Previous high radiation doses
- Long-term low-level doses sustained over several years
Major types of late effects
- carcinogenesis ( stochastic)
- Cataractogenesis ( deterministic)
- Embryonic effects ( birth defects)(stochastic)
Carcinogenesis
- the formation of cancer whereby normal cells are transformed into cancer cells.
- Cause cancer as a late stochastic effect
- At high doses the risk is measurable in a human population.
- Severity is not dose related
Cataractogenesis
- a process by which a cataract forms.
- Lens direct rays to the retina so that an image is formed
- Cataracts is the clouding of the lens of the eye .
- Once ionizing radiation reach the eye they interact with the lens causing cataracts.
- Probability that a single dose of ionization ( 2GY) will induce the formation of cataracts.
Embryonic effects ( birth defects)
- Embryonic cells begin dividing and differentiating after conception, so they are highly radiosensitive and hence may easily be damaged by ionizing radiation.
Gestation in humans is divided into 3 stages.
- pre implantation ( 0-9 days after conception)
- Organogenesis ( 10 days -12 weeks after conception.
- Fetal stage(term)
Effects of embryonic effects on newly born babie.
- growth inhibition
- Mental retardation
- Microcephaly
- Genital deformity
- Sense organ damage
Somatic effects of radiation exposure on human cells
- somatic effects refers to the biological damage caused by ionizing radiation on living organisms.
- Amount of biological damage depends on dose received.
Genetic effects
- Radiation induced genetic effect is the damage to the genes and chromosomes of the germ cell( ova and sperm)
- Biological damage to the chromosomes brings about faulty recombination of molecules that make up the chromosomes.
- The biological code contained in the chromosomes gets altered and results into an abnormality.
- No threshold dose
Examples of genetic effects
- Genital malformation
- Early deaths
- Radiation induced cancer
Effects on blood cells
- Hematologic depression
- Depletion of immature blood cells
- Stem cells of hematopoietic system
- Neutrophils
- Lymphocytes
- Thrombocytes
Hematologic depression
- ionizing radiation affects blood cells by depressing the number of cells in peripheral circulation.
*Whole body dose of 0.25 Gy delivered within a few days produces a measurable hematological depression.
Depletion of immature blood cells
- blood cells are manufactured in the bone marrow
- Radiation decreases the number of immature blood cells, hence reduction in number of mature blood cells.
- Higher radiation dose received= greater severity of cell depletion.
stem cells of hematopoietic system
- Radiation affects the stem cells of hematopoietic system
- Erythrocytes are among the most sensitive of human tissue
Lymphocytes
- live for 24 hrs
- Most radiosensitive cells in human body, if destroyed body’s immune system decreases.
- Radiation dose of 0.25 Gy to cause damage.
- Dose greater than 0.2 Gy removes most lymphocytes, thus the body is weak and takes longer to restore it’s power.
Neutrophils
- part of immune system
- If destroyed the body is prone to infections and problems.
- Dose Ms of 0.5 Gy means 90% of them will die, but the # is restored after few months.
Thrombocytes( platelets)
- initiate blood clotting this preventing hamorrhaging.
- Life span of 30 days
- Doses greater than 0.5Gy decreases their number in circulation.
- 1- 10 Gy depletes them significantly, and restored after 2 months
Effects on tissues
- effects on:
1. Muscle and epithelial tissues
2. Nervous tissue
Epithelial tissues
- line and cover the body surfaces
- No blood vessels and constantly regenerate through mitosis therefore radiosensitive.
Muscle tissues
- Highly specialized and do not divide therefore not radiosensitive.
Nervous tissue
- found in the brain and spinal cord
- Do not divide
- Have nucleus if destroyed never restored.
- Radiation can cause permanent or temporary damage to nerve processes.
- Whole body exposure at high doses can damage CNS
- Single dose of 50Gy can cause death within days or hours
Effects on spermatogonia
- mature sperms are specialized therefore insensitive to radiation while immature are not specialized therefore radiosensitive.
- 2gy can cause temporary sterility and 3gy can cause permanent sterility.
- 0.1 Gy could depress sperm population. And can mutation to future generations.
Effects on ova
- immature ova are more radiosensitive while mature over are less radiosensitive
- A dose of 5Gy may cause permanent sterility in women and 2Gy temporary sterility.
