Cell Injury Lecture Notes PDF

# Cell Injury The lecture was prepared by Aigerim Shabykeeva. ## Plan of the lesson * Introduction * Causes of the cell injury * Reversible Injury * Morphological changes in the Reversible injury * General Principles of the Cell injury * Mechanism of the cell injury ## Introduction * The cells...

# Cell Injury The lecture was prepared by Aigerim Shabykeeva. ## Plan of the lesson * Introduction * Causes of the cell injury * Reversible Injury * Morphological changes in the Reversible injury * General Principles of the Cell injury * Mechanism of the cell injury ## Introduction * The cells of the body actively interact with the environment. * Body cells regulate their structure and function to adapt to changing conditions and stress. * **Homeostasis** is the maintenance of the internal environment of the cell within acceptable limits. * Cells can adapt when faced with physical stress (increased workload) or harmful conditions (nutrient deficiency). * Cells retain their viability and function after adaptation. * Cell injury develops if adaptive capacity or stress is exceeded. * Cell injury can be reversible with little exposure to negative factors (cells return to their original state). * Irreversible cell injury or cell death develops with prolonged exposure to negative factors. * Cell death is also a normal and important process in embryogenesis, the development of organs and tissues, and the maintenance of homeostasis. ## Causes of the cell injury * **Hypoxia and ischemia**. Hypoxia (oxygen deficiency) and ischemia (reduced blood supply) are the most common causes of cell injury. Hypoxia and ischemia deprive tissues of oxygen and nutrients. * **Toxins**. Toxins are found daily in the environment (carbon dioxide, cigarette smoke, alcohol, drugs, and many medicine at therapeutic doses can cause damage to cells or tissues). * **Infectious agents**. All viruses, bacteria, fungi and protozoa can damage cells. * **Physical agents** (trauma, high air temperature, radiation, electric current and changes in atmospheric pressure). * **Immunological reactions** can also damage body cells (autoimmune reactions, allergic reactions). * **Genetic abnormalities** can damage cells as a result of a deficiency in functional proteins. * **Nutritional imbalances** are the main cause of cell injury. * **Aging** reduces the ability of cells to respond to stress and ultimately cell death. ## Reversible Injury * **Reversible injury** is the stage of cell injury at which impaired function and morphology can return to normal when negative factors are eliminated. * Cells and intracellular organelles usually swell because they absorb water and cell homeostasis is disrupted in reversible injury. ## Morpholigical changes in the Reversible injury There are two morphological changes in reversible injury: cellular edema and fatty changes. * **Cell edema** is clearly visible at the level of the whole organ. Paleness, increased turgor, an increase in the mass of the organ is observed during macroscopic examination. Small vacuoles can be seen under microscopic examination in the cytoplasm of cells. * **Fatty changes** are formed in the cytoplasm of cells. Other changes associated with cell damage include: * The cytoplasm of damaged cells may be more red. * Swelling of the plasma membrane. * Weakening of the intercellular connections. * Accumulation of the chromatin. * Amorphous formations are formed. * The cytoplasm may have "myelin figures" (aggregations of phospholipids). ## General Principles of the Cell Injury * Cellular response to a traumatic factor depends on the type of injury, its duration and severity. * The result of the action of the traumatic factor depends on the type of cell, the adaptability of the cell and the genetic composition of the cell. * Cell injury usually results from functional and biochemical abnormalities in one or more major cellular components. * Cell functions are lost far before biochemical and morphological manifestations of injury become detectable. ## Mechanism of the cell injury ### Hypoxia and Ischemia * Hypoxia is "reduction of oxygen supply to tissues below physiological levels". * It is an extremely important and common cause of cell injury and death. **Types of Hypoxia** 1. **Anemic hypoxia** is a decrease in oxygen in the blood due to a decrease in hemoglobin (hemolytic anemia, iron deficiency anemia). 2. **Histotoxic hypoxia** develops due to impaired oxygen utilization by tissues (carbon monoxide poisoning). 3. **Hypoxic hypoxia** develops due to insufficient oxygen supply to the blood (drowning). 4. **Ischemic hypoxia** develops due to impaired blood supply to tissues. 5. **Stagnant hypoxia** develops due to inadequate blood supply (cardiopulmonary failure). ### Mechanism of the Hypoxic Cell Injury * The generation of ATP (energy) slows down. * Failure of Na+ - K+ Pump. * The decrease in ATP (energy) stimulates anaerobic glycolysis to maintain the cell's energy. * Glycolysis results in the accumulation of lactic acid and inorganic phosphates inside the cell. * Protein synthesis decreases and lipids accumulate inside the cell. * All the above disturbances are reversible if oxygenation is restored. ### Toxins * Toxins induce cell injury. * Different types of toxins induce cell injury by two general mechanism: * **Direct-acting toxins**. Some toxins act directly by combining with a critical molecular component or cellular organelle. * **Latent toxins**. Many toxic substances are inactive, but they pass into reactive metabolites that act on cells. Such toxins usually affect the cells in which they are activated.