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File:IPLab12RadiationFibrosis13.jpg|This is a high-power photomicrograph of a recanalized blood vessel in the lung. Notice the anthracotic pigment adjacent to the vessel (arrows).
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== Study Questions ==
* <spoiler text="Why is the lung particularly vulnerable to radiation injury?">The lungs are extremely vascular; thus, the radiation changes seen in the vasculature can have a profound effect on the lungs. During the immediate post-irradiation period, endothelial cell swelling and vacuolization can be seen in the alveolar capillaries. The increased vascular permeability may lead to marked pulmonary congestion and edema and the other changes similar to those encountered in adult respiratory distress syndrome.</spoiler>
* <spoiler text="What types of long-term consequences does radiation injury of the lung cause?">Long-term pulmonary consequences of radiation injury include fibrosis of the alveolar walls as well as the vascular changes seen in the previous case (vessel narrowing). The respiratory dysfunction due to the combined alveolar wall fibrosis and thickening as well as the poor perfusion due to the vascular lesions can severely inhibit pulmonary function. This radiation pneumonitis creates a profound alveolocapillary block.</spoiler>
* <spoiler text="What are the vascular changes seen in radiation injury and what are the consequences of these changes?">Vascular changes, which are dose/rate dependent, are prominent in all irradiated tissues.
Endothelial cells are not specifically radiosensitive but with high exposure vascular changes can occur. There is endothelial swelling and vacuolation or even death of the endothelial cells which can then lead to secondary thrombosis or hemorrhage.
At later time points, intimal hyperplasia and fibrosis occurs which results in thickening of the vessel wall and narrowing of the vessel lumen. These vascular changes can lead to poor blood flow to the tissues.</spoiler>
* <spoiler text="Why are the fibroblasts in these areas of fibrosis so abnormal?">Radiation can lead to alterations in the mitotic process resulting in cells that have abnormal mitotic figures. These changes can lead to death of the cell.
Subtle genetic injuries, such as DNA strand breaks, are responsible for translocations and deletions. These changes lead to the mutagenic, teratogenic, and carcinogenic potentials of ionizing radiation that become evident many years after the radiation exposure. During this long time interval, sequential mitotic divisions are occurring that will ultimately lead to these untoward consequences. This phenomenon is known as radiation "latency."</spoiler>
{{IPLab 12}}
[[Category: IPLab:Lab 12]]