Gross and Microscopic Pathology of Tissue Stress Flashcards
Describe the gross and microscopic pathophysiology of at fat/enzymatic necrosis.
Gross
- White chalky deposits (saponification)
Microscopic
- Inflammation (edema)
- Loss of nuclei
- Destruction of tissue
Describe the biochemistry of a fatty necrosis.
Saponification is a process that produces soap, usually from fats and lye.
The released lipases split the triglyceride esters contained within fat cells. The fatty acids, so derived, combine with calcium to produce grossly visible chalky-white areas (fat saponification), which enable the surgeon and the pathologist to identify the lesions (Fig. 2-14). On histologic examination the necrosis takes the form of foci of shadowy outlines of necrotic fat cells, with basophilic calcium deposits, surrounded by an inflammatory reaction. (Kumar 44)
When looking at the microscopic lesion, what feature is most helpful in determining that the tissue is necrotic?
No staining nuclei
What is the large area of red in the head of the pancreas?
Hemorrhage - the fat necrosis also destroys vessels which bleed.
Once fat has become necrotic, can it become healthy fat again? Is fat necrosis reversible?
No. In the pancreas, once the tissue dies and becomes necrotic, that area is dead forever.
Things are different in the liver. Acute liver necrosis may be able to be regenerated.
What has happened to all the cells in the heart? (92 y/o female, expired)
Atrophy results in decreased size and metabolic activity of the cell. In our patient, this adaptive response occurred in response to decreased workload. Elderly patients often become increasingly sedentary, thus reducing cardiac demand. Correspondingly, the metabolic activity of the cardiac myocytes decreases and they become smaller.
Describe the physiologic mechanisms the result in cardiac atrophy associated with aging; where did the cellular proteins go? How where the proteins removed?
The UPS and autophagy-lysosomal systems are the two main protein degradation systems in the cell. Generally, proteins tagged with polyubiquitin chains become substrates for the UPS system where they are degraded into smaller, digested peptides. Some ubiquitinated substrates can also be degraded via the autophagy-lysosomal system. This system is composed of:
Macroautophagy
Cytosolic components are engulfed and delivered to the lysosome in bulk
Microautophagy
Small volumes of cytosol are directly engulfed by lysosomes
Chaperone-mediated autophagy
Soluble substrates associated with a specific chaperone complex are translocated into the lysosome via a lysosomal receptor (LAMP-2A)
*Atrophy is frequently associated with increased autophagy.
1)What is the brown material near the nuclei seen in the microscopic image? Where did it come from?
Note the brown pigment granules located within the cytoplasm of the cardiac myocytes. This pigment is called lipofuscin or lipochrome and accumulates as part of normal wear and tear.
Lipofuscin is formed as a result of free radical injury and lipid peroxidation, but is not injurious to the cell or its functions.
In tissue sections, lipofuscin appears as brown-yellow, finely granular, cytoplasmic, often perinuclear, pigment.
Lipofuscin accumulates in cells undergoing slow, regressive changes and is particularly prominent in the heart and liver of aging patients as well as patients suffering from malnutrition or cancer cachexia. It is formed during the process of autophagy.
Liquefactive necrosis. In liquefactive necrosis, cells are lysed and converted to a fluid phase. Eventually all the parenchymal cells are completely lysed or phagocytized, and all that remains is the vasculature and intervening spaces.
There are no fibroblasts in the brain. If a scar could form in the brain, it would result in contracture of the brain parenchyma, causing even more damage.
Brain tissue does not contain lymphatic vessels, therefore, necrotic tissue is removed via cerebrospinal fluid and the glymphatic system.
This is an image of the myocardium from a patient who had an MI. Describe the appearance of these cells.
- Are they normal?
Relatively normal myocardium…
Cells have nuclei and the cytoplasm is light pink. There is abnormal edema around the myocytes (empty white spaces).
This is an image of the myocardium from a patient who had an MI. Describe the appearance of these cells.
Are they normal?
Inflammation around the infarct…
Neutrophils in the interstitium around the infarcted zone.
This is an image of the myocardium from a patient who had an MI. Describe the appearance of these cells.
Are they normal?
Dead myocardium…
Dead, infarcted myocardium. The myocytes have no stainable nuclei. Edema and proteinaceous debris surround the myocytes.
Cells in the center of the myocardial infarct experience death through […].
Cells in the periphery of the infarct are under stress and tend toward […].
Necrosis
Apoptosis
