Pathophysiology

Pathophysiology Study Guide

Mechanisms of Cell Injury There are a variety of factors that may lead to cell injury. Some of the injurious stimuli for cells are: • Hypoxia: Also known as a deficiency of oxygen, hypoxia is one of the most common mechanisms leading to cell injury and death. With hypoxia, there is interference in the aerobic oxidative respiration. Causes of hypoxia include a loss of blood supply in the body tissues, as in ischemia, inadequate oxygenation of blood, like in pneumonia, and a reduction in the capacity of the blood to carry blood, as in anemia or carbon monoxide poisoning. • Hyperoxia/free radicals: As opposed to hypoxia, hyperoxia is when the tissues and organs in the body receive more blood than the required partial pressure of oxygen. This leads to oxygen toxicity. The human body can tolerate mild levels of hyperoxia, but in extreme cases, pulmonary damage occurs. Hyperoxia may result in an elevated level of reactive oxygen molecules containing a chemical with the capacity to react. These molecules react with the tissues and cause injury to DNA, nucleic acids, and lipids. Major symptoms of hyperoxia are edema of lungs, irritation, and congestion, which may lead to death in the case of prolonged exposure. • Nutritional deficits: One possible cause of cell injury is protein deficiency; it is the most common reason for cellular injury in disadvantaged people. Even in developed populations, vitamin deficiency is a large cause of cell injury. An excess of calories can also cause morbidity and death. For example, an excess of calories may cause obesity, which can lead to diabetes type 2 mellitus. Moreover, animal-fat rich food items are likely to cause diseases like atherosclerosis, and disorders including cancer. • Chemical injury: Chemical substances, in abundance, have the ability to cause injury and death of cells. Glucose and salt, in concentrated form, disrupt the osmotic environment. Similarly, the high partial pressure of oxygen becomes toxic. Many chemical agents, which are toxic and poisonous, include insecticides, pollutants in the air, carbon monoxide, asbestos, and ethanol. These chemical agents damage the cell after altering the permeability of the membrane, osmotic homeostasis, and disturbing the enzyme integrity, which can eventually lead to the death of the entire organism. Further, inappropriate use of therapeutic drugs also leads to injury of the cells and tissues. • Infectious agents: A large number of microorganisms and species in the environment have the ability to cause infections, which aid in damaging cells and tissues in the body. These agents could be as minute as viruses seen from microscopes to as long as tapeworms measured in meters. Bacteria, fungi, protozoans, and rickettsia are some other agents that are infectious pathogens and cause cell injury. • Physical andmechanical injury: Both physical andmechanical reasons can cause injury to cells. Examples include trauma, extreme temperatures, exposure to radiation, electric shock, and sudden and drastic changes in atmospheric pressure. Intracellular Accumulation Sometimes cells can accumulate different substances, which can either be harmless or cause cell injury and death. These collections can be stored in various parts of the cell, which range from the cytoplasm of the cell, lysosomes in organelles, and nucleus. They can also be transmitted from the

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