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Radiobiology And Protection > Effects Of Radiation Exposure On Human Cells > Flashcards

Effects Of Radiation Exposure On Human Cells Flashcards

1
Q

Identify effects of radiation exposure on human cells

A
  • early effects
  • Late effects
  • Somatic effects
  • Genetic effects
  • Effects on blood cells
  • Effects on tissues
  • Effects on reproductive cells
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2
Q

early effects

A
  • 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
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3
Q

possible high dose consequences of late effects

A

*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

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3
Q

what name is given to deterministic effects.

A
  • Acute radiation syndrome.(ARS)
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3
Q

Under what conditions does ARS occur in humans.

A

*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;

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3
Q

Late effects

A
  • Effects appear months or years after
    exposure to irradiation.
  • Radiation induced at cellular level may lead to measurable somatic and hereditary damage.
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3
Q

late effects may result from

A
  • Previous whole-or partial body acute exposure
  • Previous high radiation doses
  • Long-term low-level doses sustained over several years
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4
Q

Major types of late effects

A
  • carcinogenesis ( stochastic)
  • Cataractogenesis ( deterministic)
  • Embryonic effects ( birth defects)(stochastic)
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4
Q

Carcinogenesis

A
  • 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
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4
Q

Cataractogenesis

A
  • 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.
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5
Q

Embryonic effects ( birth defects)

A
  • Embryonic cells begin dividing and differentiating after conception, so they are highly radiosensitive and hence may easily be damaged by ionizing radiation.
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6
Q

Gestation in humans is divided into 3 stages.

A
  • pre implantation ( 0-9 days after conception)
  • Organogenesis ( 10 days -12 weeks after conception.
  • Fetal stage(term)
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7
Q

Effects of embryonic effects on newly born babie.

A
  • growth inhibition
  • Mental retardation
  • Microcephaly
  • Genital deformity
  • Sense organ damage
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8
Q

Somatic effects of radiation exposure on human cells

A
  • somatic effects refers to the biological damage caused by ionizing radiation on living organisms.
  • Amount of biological damage depends on dose received.
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9
Q

Genetic effects

A
  • 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
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10
Q

Examples of genetic effects

A
  • Genital malformation
  • Early deaths
  • Radiation induced cancer
11
Q

Effects on blood cells

A
  • Hematologic depression
  • Depletion of immature blood cells
  • Stem cells of hematopoietic system
  • Neutrophils
  • Lymphocytes
  • Thrombocytes
12
Q

Hematologic depression

A
  • 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.
13
Q

Depletion of immature blood cells

A
  • 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.
14
Q

stem cells of hematopoietic system

A
  • Radiation affects the stem cells of hematopoietic system
  • Erythrocytes are among the most sensitive of human tissue
15
Q

Lymphocytes

A
  • 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.
16
Q

Neutrophils

A
  • 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.
17
Q

Thrombocytes( platelets)

A
  • 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
18
Q

Effects on tissues

A
  • effects on:
    1. Muscle and epithelial tissues
    2. Nervous tissue
19
Q

Epithelial tissues

A
  • line and cover the body surfaces
  • No blood vessels and constantly regenerate through mitosis therefore radiosensitive.
20
Q

Muscle tissues

A
  • Highly specialized and do not divide therefore not radiosensitive.
21
Q

Nervous tissue

A
  • 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
22
Q

Effects on spermatogonia

A
  • 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.
23
Q

Effects on ova

A
  • 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.

Radiobiology And Protection (9 decks)

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