Lecture #4.1: Intracellular Accumultions & Necrosis Flashcards
where are intracellular accumulations most common?
more often in the cytoplasm (phagolysosomes) but also in the nucleus
What is the main cause of intracellular accumulations?
metabolic alterations
what do intracellular accumulations consist of?
- normal cellular constituents (water, lipids, carbs and proteins)
- abnormal substances (minerals, products of infectious agents, products of abnormal metabolism)
- pigments
how can abnormal intracellular accumulations occur? (mechanisms)
- a normal endogenous substance is produced at a normal or increased rate but the metabolism is inadequate to remove it (ex: steatosis)
- a normal or abnormal endogenous substance that accumulates because of genetic or acquired defects in the metabolism, packaging, transport or secretion (ex: enzyme deficiencies resulting in the accumulation of lipids, proteins and carbohydrates)
- an abnormal exogenous substance that accumulates due to the inability to degrade or transport it (ex: carbon or silica particles)
what is steatosis?
intracellular accumulation of triglycerides in the liver
what is hepatic lipidosis (fatty liver or hepatic steatosis)?
an accumulation of lipids or triglycerides in the liver
what are the types of pigments accumulation?
- hyaline
- lipofuscin
- hemosiderin
- bilirubin
- exogenous pigmetns-> anthracosis
what is hyaline?
a substance (often protein) that has a homogeneous, glassy eosinophilic appearance
what is lipofuscin?
a golden brown pigment caused from lipids peroxidation (deficiency of Vit E or Selenium)
what is hemosiderin?
iron containing yellow-brown pigments, derived from hemoglobin (breakdown of RBCs), represents aggregates of ferritin
what is bilirubin (icterus or jaundice)?
accumulates in hemolytic diseases, failure of conjugation or excretion
what is anthracosis? what kind of pigment is it?
the storage of carbon particles in lung and lymph nodes (miner’s lungs). it is an exogenous pigments
what are the 5 histological classifications of necrotic lesions?
- Coagulative necrosis
- Liquefactive necrosis
- Caseous necrosis
- Fat necrosis
- Gangrene
what is the most common form of necrosis?
Coagulative necrosis
what are some characteristics of Coagulative necrosis?
- results from sudden & severe ischemia (often occurs in heart, kidney & adrenal tissue)
- morphological appearance of boiled meat (coagulated protein)
- denaturation of proteins (only the outline of cells can be seen, cytoplasm is eosinophilic, nuclei are pyknotic or absent)
- tissue organization is preserved but cellular details are lost
- over time affected cells are removed by phagocytosis and action of proteolytic lysosomal enzymes
what are some characteristics of liquefactive necrosis?
- characteristic of focal bacterial or fungal infections (accumulation of inflammatory cells), and hypoxic death of cells in the CNS
- dissolution of the cells (the affected tissue is liquefied)
- transformation of the tissue into a liquid viscous mass (enzymatic degradation; neutrophils, lysosomes)
- presence of pus if the process is initiated by acute inflammation (extensive infiltration of neutrophils-abscess)
what is encephalomalacia?
hypoxic death of cells in the brain
what is myelomalacia?
hypoxic death of cells in the spinal cord
what are some characterisitcs of caseous necrosis?
- distinct form of coagulative necrosis where coagulated dead cells are converted into granular friable mass
- amorphous granular debris
- necrotic tissue with the appearance of “cottage cheese” (soft and pasty)
- combination of coagulative and liquefactive necrosis (coagulative necrosis with limited liquefaction)
where do we mostly see caseous necrosis?
encountered most often in foci of tuberculosis infection
what is characteristics of fat necrosis?
- focal area of fat destruction
- type of liquefactive necrosis but does not denote a specific pattern of necrosis
- necrosis of fat due to action of enzymes (pancreatic lipases) followed by formation of complexes with calcium
- fatty acids combine with calcium to create a “calcium soap” (white chalky deposits)
what is characteristic of gangrenous necrosis or gangrene?
- usually applied to necrosis of extremities (limbs, digits, and tips of the ears)
- not a distinctive pattern of cell death (no clear differences from liqurefactive or coagulative)
what type of necrosis is dry gangrene?
coagulative (ischemic)
what type of necrosis is wet gangrene?
liquefactive (bacterial)
