Cell Injury 2 Basics Flashcards
Define: Necrosis
a sequence of morphological changes that follow irreversible injury and cell death in a tissue
Describe two biochemical processes that can occur in necrosis.
Cell changes may be accomplished by 1) enzymatic digestion or 2) denaturation of proteins. If the source of the hydrolytic enzymes is from the dead cells themselves the process is called autolysis. If the enzymes originate from inflammatory cells that invade the necrotic focus, the process is termed heterolysis.
Describe coagulation necrosis.
This is the most common form of necrosis and occurs in a number of solid organs. Hypoxic death of cells in all tissues except brain will result in a coagulation necrosis. In this form the structural outline of elements of the tissue is preserved for days.
What are the histological characteristics of coagulation necrosis?
Histologically, the necrotic tissue contains eosinophilic ghosts of structures or cells that are devoid of nuclear detail. The necrotic area may have an inflammatory infiltrate.
Describe liquefactive necrosis.
This necrosis occurs in any tissue where there is a focus of bacterial or fungal infection (abscess). The focus will attract inflammatory cells that contribute enzymes for digestion (pus). This process obliterates the structure of tissue. Liquefactive necrosis is the necrosis affecting the central nervous system even without bacterial involvement. Large hemorrhages of the brain leave empty cavities when the liquid debris is resolved.
What are the histological characteristics of liquefactive necrosis?
This process obliterates the structure of tissue, leaving nothing resembling the previously existing cell behind.
Describe gangrenous necrosis.
Normally this type of necrosis involves the distal region of the limb (most often leg). Loss of blood supply initiates a coagulative necrosis with a superimposed bacterial infection (wet gangrene).
Describe caseous necrosis.
This type of necrosis is a form of coagulation necrosis at the focus of a tuberculous infection. It is seen in the lung and any other tissue affected by tuberculosis. The necrotic area is white and cheesy and devoid of structure but surrounded by a ring of granulomatous inflammation. Once resolved this too leaves cavities at the site.
What are the histological characteristics of caseous necrosis?
the necrotic area is white and cheesy and devoid of structure, but is surrounded by a ring of granulomatous inflammation. Eventually there will remain a cavity in the previous site.
Describe fat necrosis.
Enzymatic fat necrosis may be seen in focal areas of the peritoneal cavity and is caused by release of pancreatic enzymes into the peritoneum. The pancreatic lipases attack the fat associated with the mesenteries and omentum hydrolyzing triglyceride esters to release fatty acids. The fatty acids combine with calcium to form chalky white areas (fat saponification). Histologically these calcium soaps appear as pale basophilic amorphic foci. Traumatic fat necrosis is seen in the breast.
What are the histological characteristics of fat necrosis?
white chalky areas
Define: Calcification
an abnormal deposition of calcium salts and other types of minerals in tissues
What are the two types of calcification?
dystrophic and metastatic
Describe: Dystrophic Calcification
It occurs in areas of necrosis despite normal circulating levels of calcium. Crystal formation begins as calcium combines with phosphate to form a hydroxyapatite-like deposit in the dead cells or mitochondria of the necrotic tissues. In some cases these sites may initiate heterotopic bone formation. Dystrophic calcification can contribute to further organ dysfunction.
Describe: Metastatic Calcification
It occurs in normal tissues. Abnormally high levels of circulating calcium (hypercalcemia) due to endocrine dysfunction or a tumor causing bone destruction are the cause of this sort of calcium deposition.
Define: Apoptosis
programmed cell death
What are some major differences between apoptosis and necrosis?
cell size: necrosis-swelling, apoptosis-shrinkage;
nucleus: necrosis-pyknosis to karyorrhexis to karyolysis, apoptosis-fragmentation;
plasma membrane: necrosis-disrupted, apoptosis-intact;
cellular contents: necrosis-enzymatic digestion may leak out, apoptosis-intact may be apoptotic bodies;
inflammation: necrosis-frequent, apoptosis-none
regulation: necrosis-unregulated process, apoptosis-highly regulated process
Describe the morphology of apoptosis.
Morphologically, the nucleus of the apoptotic cell exhibits a distinctive condensation of chromatin which is followed by formation of nuclear fragments. The plasma membrane of the apoptotic cell remains intact and packages budding cytoplasmic fragments containing organelles and nuclear fragments into discrete apoptotic bodies that are quickly phagocytosed by macrophages and other cells without inflammation. If DNA is isolated from apoptotic cells, necrotic cells and viable cells and subjected to electrophoretic separation, distinct differences are observed. The control DNA runs as a single band while the DNA isolated from the necrotic cells will travel as a streaked band due to general degradation. The DNA from apoptotic cells forms distinct subunits or fragments that “ladder” along the band of the gel. This observation was once considered the best experimental indicator of apoptosis but once the biochemical pathways for this activity have been clarified , it would seem that assays for specific caspases are better indicators.
Name three events that involve physiologic apoptosis.
limb development, implantation, organogenesis, developmental involution, and metamorphosis
Define: Autolysis
spontaneous degredation of cells or tissues by enzymes produced by the organism, as occurs after death and in some pathologic conditions. Enzymatic digestion results from the catalytic enzymes derived from the lysosomes of the dead cell themselves.
Define: Heterolysis
Cell death resulting from the catalytic enzymes derived from the lysosomes of immigrate leukocytes.
Define: Atrophy
Decrease in cell size.
Define: Hypertrophy
Increase in cell size.
Define: Hyperplasia
Increase in mitosis resulting in a greater number of cells.
Define: Metaplasia
change in the state of differentiation of a cell in response to stress, most commonly an irritation.
Define: Dysplasia
Abnormality in development; in pathology, alteration in size, shape, and organization of adult cells
What is the most common form of necrosis?
coagulation necrosis
What type of necrosis occurs in any tissue where there has been a bacterial or fungal infection (abscess)?
liquefactive necrosis
What type of necrosis is found in tissues affected by tuberculosis?
caseous necrosis
What form of necrosis affects the cetnral nervous system and brain?
liquefactive necrosis
What type of necrosis is often found in distal limbs?
gangrenous necrosis
What type of necrosis is characterized by chalky white areas?
fat necrosis; the chalky white areas are called fat suponification.
What adaptations can lead to an incrase in organ size? A. atrophy B. hypertrophy C. hyperplasia D. metaplasia
B. hypertrophy and C. hyperplasia
What cell adaptation leads to a decrease in cell or organ size? A. atrophy B. hypertrophy C. hyperplasia D. metaplasia
A. atrophy
