Textbook readings

• Cells respond to environmental changes in 3 different ways: reversible cell injury, adaptation and cell death
• Apoptosis is physiological process but could also be pathological in some cases
• Reversible injuries and early stages of irreversible cause cellular swelling
• Hydropic swelling or oncosis: Swelling that occurs due to accumulated water. Occurs from the malfunction of the Na/K pump. Is defined by large/pale cytoplasm and dilated ER + mitochondria.
• In some cases, cell accumulations don't cause injury themselves but are indicators of cell injury
• Cell accumulations could results in injury due to toxicity, provoking an immune response or occupying too much space
• Intracellular accumulations are categorized by excess amounts of normal substances(lipids), abnormal substances(occurs cuz of faulty metabolism) and pigments or particles that can't be degraded
• A common site of intracellular lipid accumulation is the liver
• Intracellular accumulation can occur because the enzymes/mechanisms to break things down are impaired
• Cellular stress may lead to accumulation of denatured proteins. These are then handled using protein chaperones and ubiquitin to degrade them in a proteosome
• Endogenous means produced within the body while exogenous means that introduced externally
• The pigments melanin, hemosiderin and bilirubin indicate disease processes in excess amounts
• Inorganic particles likes calcium or mineral dusts can be inhaled to cause chronic inflammation in the lung; this destroys alveoli and capillaries to form scar tissue. Extensive scarring cause the lungs to become stiff and hard to expand
• Calcification of the heart valves could cause cardiac ischemia; dead and dying tissues usually become calcified
• Lung damage resulting from tuberculosis appears as calcified area called tubercles
• With the exception of inorganic particles, intracellular accumulations are reversible if the causative factors are removed
• In some cases, adaptive changes are not beneficial
• Common adaptive changes are atrophy, hypertrophy, hyperplasia, metaplasia and dysplasia; each of these are reversible when the cellular stress is relieved
• Atrophy occurs when cells shrink and reduce their fxns in response to normal and injurious factors.
• Atrophy occurs bcuz of disuse, denervation, ischemia, malnourishment, interruption of endocrine signals and persistent cell injury.
• Hypertrophy is an increase in cell mass that comes with better functional capacity
• Organ enlargement occurs bcuz of hypertrophy and hyperplasia
• Hyperplasia is the increase of the number of cells and an example is an increase of RBCs in response to hypoxia
• Metaplasia is the replacement of one differentiated cell type with another
• Necrotic cells show these changes: shrunken nucleus, swollen cell volume and disrupted plasma and organelle membranes
• Necrosis causes general inflammation, increased heart rate, WBC count and a loss of appetite and fever
• There are 4 different types of tissue necrosis: coagulative, liquefactive, fat and caseous
• Coagulative necrosis is the most common
• Steps leading to coagulative necrosis are : ischemic cell injury, loss of ability to maintain electrochemical gradient, influx of calcium ions/mitochondrial dysfunction and degeneration of plasma membrane and structures
• The area of coagulative necrosis is composed of denatured proteins
• Liquefactive necrosis often forms an abscess or a cyst
• Fat necrosis occurs bcuz of trauma or pancreatitis. It refers to death of adipose tissue
• Caseous necrosis is specific to lung tissue damaged by tuberculosis
• Gangrene describes cellular death involving a large area of tissue
• Gangrene occurs bcuz of ischemia to body parts and depending on its appearance, it can described as wet, dry and gas
• Dry gangrene is a type of coagulative necrosis characterized by blackened tissue that only occurs on the extremities
• Wet gangrene is caused by liquefaction and occurs in internal organs; the rapid spread of tissue damage and toxins into the bloodstream make this a life-threatening problem
• Gas gangrene is characterized by the formation of gas bubbles in damaged tissue.
• Apoptosis has no inflammation in its process at all
• Apoptosis can also be implicated in response to pathologic cell death/disease; In an MI, about 20% of cell death is necrotic and the rest is apoptotic