Myocarditis is caused by infectious (coxsackie A and B viruses, Chagas disease) andimmune causes. Clinically, the patient may be asymptomatic or may suffer from acute heart failure or even dilated cardiomyopathy.
CELLULAR ADAPTIVE RESPONSES TO INJURY In general, cellular adaptation is a potentially reversible change in response to the environment. Atrophy is a decrease in cell/organ size and functional ability. Causes of atrophyinclude decreased workload/disuse (immobilization); ischemia (atherosclerosis); lack of hormonal or neural stimulation, malnutrition, and aging. Light microscopic examination shows small shrunken cells with lipofuscin granules. Electron microscopy shows decreased intracellular components and autophagosomes. Hypertrophy is an increase in cell size and functional ability due to increased syn-thesis of intracellular components. Causes of hypertrophy include: · Increased mechanical demand can be physiologic (striated muscle of weight lifters) or pathologic (cardiac muscle in hypertension). · Increased endoc...
CELL DEATH Morphologic types of necrosis (cell death in living tissue, often with an inflamma-tory response) are as follows: · Coagulative necrosis , the most common form of necrosis, is most often due toischemic injury (infarct). It is caused by the denaturing of proteins within the cytoplasm. Microscopic examination shows loss of the nucleus but preservation of cellular shape. Coagulative necrosis is common in most organs, including the heart, liver, and kidney, but not the brain. · Liquefaction necrosis results from cellular destruction by hydrolytic enzymes,leading to autolysis (release of proteolytic enzymes from injured cells) and het-erolysis (release of proteolytic enzymes from inflammatory cells). Liquefaction necrosis occurs in abscesses, brain infarcts, and pancreatic necrosis. · ...
CAUSES OF CELLULAR INJURY Hypoxia is the most common cause of injury; it occurs when lack of oxygen preventsthe cell from synthesizing sufficient ATP by aerobic oxidation. Major mechanisms leading to hypoxia are ischemia, cardiopulmonary failure, and decreased oxygen-carrying capacity of the blood (e.g., anemia). Ischemia , due to a loss of blood supply, is the most common cause of hypoxia, and is typically related to decreased arterial flow or decreased venous outflow (e.g., atherosclerosis, thrombus, thromboembolus). Pathogens (viruses, bacteria, parasites, fungi, and prions) can injure the body bydirect infection of cells, production of toxins, or host inflammatory response. Immunologic dysfunction includes hypersensitivity reactions and autoimmune diseases. Congenital disorders are inherited genetic mutations (e.g., inborn errors of metabolism). Chemical injury can occur with drugs, poisons (cyanide, arsenic, mercury, etc.), pol-lution, occ...
Comments
Post a Comment