introduction general pathology slides from Robins pathology

slides give a brief introduction of general pathology

1. Prepared by : TAIMOOR HAIDER Lecture 1 General Pathology University of Sialkot Dept . Medical lab Tech Topic : Cell Injury & Adaptations

2. Cell Injury & Adaptations Pathology: The field of pathology is devoted to understanding the causes of disease and the changes in cells, tissues, and organs that are associated with disease. Pathogenesis refers to the mechanisms of development and progression of disease, which account for the cellular and molecular changes that give rise to the specific functional and structural abnormalities that characterize any particular disease.

3. Cell Injury Cells actively interact with their environment, Constantly adjusting their structure and function to accommodate changing demands and extracellular stresses. Within certain limits, injury is reversible, and cells return to their stable baseline. However, if the stress is severe, persistent, or rapid in onset, it results in irreversible injury and death of the affected cells.

4. CAUSES OF CELL INJURY

5. CAUSES OF CELL INJURY The causes of cell injury span a range from gross physical trauma, such as after a motor vehicle accident to a single gene defect. That results in a nonfunctional enzyme in a specific metabolic disease. Most injurious stimuli can be grouped into the following categories.

6. Hypoxia and ischemia Hypoxia, which refers to oxygen deficiency, and ischemia, which means reduced blood supply, are among the most common causes of cell injury. Both deprive tissues of oxygen, and ischemia. In addition, results in a deficiency of essential nutrients and a build up of toxic metabolites. The most common cause of hypoxia is ischemia resulting from an arterial obstruction

7. Hypoxia and ischemia oxygen deficiency also can result from inadequate oxygenation of the blood as in a variety of diseases affecting the lung, or from reduction in the oxygen-carrying capacity of the blood, as with anemia of any cause, and carbon monoxide (CO) poisoning.

8. Toxins Potentially toxic agents are encountered daily in the environment. These include air pollutants, insecticides, CO, asbestos, cigarette smoke, ethanol, and drugs. Many drugs in therapeutic doses can cause cell or tissue injury in a susceptible patient. Even innocuous substances, such as glucose, salt, water and oxygen, can be toxic.

9. Infectious agents All types of disease-causing pathogens, including viruses, bacteria, fungi, and protozoans,injure cells.

10. Immunologic reactions Although the immune system defends the body against pathogenic microbes, immune reactions also can result in cell and tissue injury. Examples are autoimmune reactions against one’s own tissues, allergic reactions against environmental substances. In all of these situations, immune responses elicit inflammatory reactions, which are often the cause of damage to cells and tissues.

11. Genetic abnormalities Genetic aberrations can result inpathologic changes as conspicuous as the congenital malformations. Genetic defects may cause cell injury as a consequence of deficiency of functional proteins.

12. Nutritional imbalances Protein–calorie insufficiency among impoverished populations remains a major cause of cell injury. Specific vitamin deficiencies are not uncommon even in developed countries with high standards of living. Ironically, excessive dietary intake may result in obesity and also is an important underlying factor in many diseases, such as type 2 diabetes mellitus and atherosclerosis.

13. Physical agents Trauma, extremes Trauma, extremes of temperature, radiation, electric shock, and sudden changes in atmospheric pressure all have wide-ranging effects on cells.

14. Aging Cellular senescence results in a diminished ability of cells to respond to stress and, eventually, the death of cells and of the organism. The progression and morphologic manifestations of cell injury, and then to the biochemical mechanisms in injury caused by different noxious stimuli.

15. SEQUENCE OF EVENTS IN CELL INJURY AND CELL DEATH Reversible injury is the stage of cell injury at which the deranged function and morphology of the injured cells can return to normal if the damaging stimulus is removed. In reversible injury, cells and intracellular organelles typically become swollen. they take in water as a result of the failure of energy-dependent ion pumps. In the plasma membrane, leading to an inability to maintain ionic and fluid homeostasis. In some forms of injury, degenerated organelles and lipids may accumulate insidethe injured cells.

16. Cell Death When cells are injured they die by different mechanisms, depending on the nature and severity of the insult. Severe disturbances, such as loss of oxygen and nutrient supply and the actions of toxins, cause a rapid and uncontrollable form of death that has been called “ accidental”cell death. Necrosis is the major pathway of cell death in many commonly encountered injuries, such as those resulting from ischemia, exposure to toxins, variousinfections , and trauma.

17. Necrosis Necrosis is a form of cell death in which cellular membranes fall apart, and cellular enzymes leak out and ultimately digest the cell.

18. Apoptosis Apoptosis is a pathway of cell death in which cells activate enzymes that degrade the cells’ own nuclear DNA and nuclear and cytoplasmic proteins .

19. Autophagy Autophagy (“self-eating”) refers to lysosomal digestion of the cell’s own components. It is a survival mechanism in times of nutrient deprivation, so that the starved cell can live by eating its own contents and recycling these contents to provide nutrients and energy.

20. Oxidative Stress Oxidative stress refers to cellular abnormalities that are induced by ROS, which belong to a group of molecules known as free radicals. Free radical-mediated cell injury is seen in many circumstances, including chemical and radiation injury, hypoxia, cellular aging, tissue injury caused by inflammatory cells, and ischemia-reperfusion injury.

21. CELLULAR ADAPTATIONS TO STRESS Adaptations are reversible changes in the number, size, phenotype, metabolic activity, or functions of cells in response to changes in their environment.

22. Hypertrophy Hypertrophy is an increase in the size of cells resulting in an increase in the size of the organ. Hypertrophy can be physiologic or pathologic and is caused either by increased functional demand or by growth factor or hormonal stimulation. The massive physiologic enlargement of the uterus during pregnancy occurs as a consequence of estrogen stimulated. An example of pathologic hypertrophy is the cardiac enlargement that occurs with hypertension or aortic valve disease

23. Hyperplasia Hyperplasia is an increase in the number of cells in an organ that stems from increased proliferation, either of differentiated cells or, in some instances, less differentiated progenitor cells. Hyperplasia can be physiologic or pathologic; in both situations, cellular proliferation is stimulated by growth factors that are produced by a variety of cell types. The two types of physiologic hyperplasia are Hormonal hyperplasia, exemplified by the proliferation of the glandular epithelium of the female breast at puberty and during pregnancy compensatory hyperplasia, in which residual tissue grows after removal or loss of part of an organ. For example, when part of a liver.

24. Atrophy Atrophy is shrinkage in the size of cells by the loss of cell substance. When a sufficient number of cells are involved, the entire tissue or organ is reduced in size, or atrophic. Although atrophic cells may have diminished function, they are not dead. Causes of atrophy include a decreased workload (e.g., immobilization of a limb to permit healing of a fracture), loss of innervation , diminished blood supply, inadequate nutrition, loss of endocrine stimulation, and aging.

25. Atrophy Although some of these stimuli are physiologic(e.g., the loss of hormone stimulation in menopause). others are pathologic (e.g., denervation ), the fundamental cellular changes are similar. Cellular atrophy results from a combination of decreased protein synthesis and increased protein degradation.

26. Metaplasia Metaplasia is a change in which one adult cell type (epithelial or mesenchymal ) is replaced by another adult cell type. In this type of cellular adaptation, a cell type sensitive to a particular stress is replaced by another cell type better able to withstand the adverse environment. Metaplasia is thought to arise by the reprogramming of stem cells.