Cell Necrosis Flashcards
Define the term Necrosis and differentiate between Necrosis and Autolysis Define the different types and Cell Necrosis and be able to give examples of each. Differentiate between Wet and Dry Gangrene Differentiate between Dystrophic and Metastatic Calcifications. List examples of Dystrophic and Metastatic Calcification
What is the definition of necrosis?
the death of cells or groups of cells within a living organism
Differentiate between necrosis and autolysis?
Necrosis is seen in the living with inflammation
autolysis is seen in tissues after death
What are the there different types of necrosis?
coagulative, liquefactive, caseous and fat
What is Coagulative Necrosis?
The most common form of necrosis. Occurs when cells proteins are altered or denatured.
when observed histologically the cell outline are preserved and the cytoplasm appears finely granular
coagulative necrosis in cells can be compared to the coagulation that occurs when cooking eggs
Examples of Coagulative Necrosis
this type of necrosis is typically observed in solid internal organs (heart, kidney. liver, spleen) and is most often caused by anoxia resulting from ischemia
Best example of Coagulative Necrosis
death of heart tissue as a result of a myocardial infarction
what leukocyte is found microscopically during examination of coagulative necrosis
neutrophils
in an Acute Myocardial Infarct you may also observe dead heart muscle cells
What is Liquefactive Necrosis?
process in which dead cells liquify under the influence of certain cell enzymes, resulting in soft and gel-like tissues
there will be a high concentration of neutrophils present
Examples of Liquefactive Necrosis
most often Liquefactive Necrosis occurs the the brain, resulting in loss of contours and liquefaction of brain cells.
loss of blood supply to the brain (i.e. stroke) causing softening and ultimately transformation into a fluid-filled cavity, common in drowning
this necrosis can also be seen in certain bacterial infections in which a cavity may develop, such as abscesses in the lungs
What is Caseous Necrosis?
a form of coagulative necrosis in which a thick yellowish and cheesy substance forms
Example of Caseous Necrosis
Tuberculosis
lung granulomas are formed encasing areas of caseous necrosis
this is called the Ghon Complex and many patients will heals, and the infection in contained within the granuloma
we may also observe cases necrosis in some fungal infections such as histoplasmosis (infection by a fungus found in the droppings of birds and bats in humid areas, not serious if contained within the lung but can be problematic or fatal if spread throughout the body)
What is Fat Necrosis?
A specialized form of liquefaction necrosis caused by the action of lipolytic enzymes
Examples of Fat Necrosis
It is limited to fat tissue, usually around the pancreas, where enzymes are released into the adjacent fat tissue, usually after rupture of the pancreas (trauma, acute pancreatitis from excessive ETHOL consumption), causing degradation of fat into glycerol and free fatty acids. The free fatty acids rapidly bind with calcium, forming soaps, causing white, calcified specks
Breast is another common site for fat necrosis, resulting in features that mimic breast cancer findings
Necrotic tissue and bacteria
Necrotic tissue can provide a good medium for infection by bacteria
Wet gangrene
The bacterial infection of coagulated tissue leads to inflammation and a secondary liquefaction clinically known as wet gangrene
an example is advanced decubitus ulcers
Dry gangrene
if the necrotic tissue dries out it become black and mummified
Give underlying conditions that contribute to Gangrene?
Gangrene infections frequently occur after an infarction of the intestines or in a limb and are usually caused be atherosclerosis or diabetes
What are Dystrophic Calcifications?
macroscopic deposition of calcium in injured or dead tissues. Represents an extracellular deposition of calcium from the circulation into dead or dying necrotic tissue, often visible to the naked eye, and range from gritty, sand-like grains to firm, rock-hard material
common in arteries
Necrotic tissue and calcium
Necrotic tissue attracts calcium salts and frequently undergoes calcification
Mammograms and Dystrophic Calcifications
Breast calcifications routinely appear on breast cancer screening mammograms.
Most breast calcifications are caused by benign breast changes
However calcifications and microcalcifications (that are smaller and usually found ‘earlier‘) are considered to be a breast cancer risk
examples of Dystrophic Calcification (4)
- Calcifications in Atherosclerotic coronary arteries contributes to narrowing of the vessels. Harder to get blood through these vessels, must use a balloon angioplasty
- Calcifications of the Mitral or Aortic valves leading to impeded blood flow (Stenosis)
- Calcifications seen around breast cancers that can be visualized by mammography.
- Infant periventricular calcifications seen in congenital Toxoplasmosis.
Toxoplasmosis
Parasitic infection, parasites can cross the placental and result in Infant periventricular calcifications
This is why we recommend pregnant women to stay away from the litter box (i.e. cleaning litter box), The parasites are commonly found ing the feces of cats and can migrate to the air and then be breathed in and cross the placental to the developing fetus
What are Metastatic Calcifications?
Reflects deranged calcium metabolism (not cell injury), usually associated with increased serum calcium levels, leading to deposition of calcium in other locations
Examples of Metastatic Calcifications
seen in various disorders including Hyperparathyroidism, vitamin D toxicity and Chronic Renal Failure.
causes formation of calcium stones in sites such as the gallbladder, kidneys and bladder due to precipitation of the salts from solution into tissues
