NECROSIS AND POSTMORTEM CHANGES Flashcards
(32 cards)
The death of a cell or group of cells in contact with living tissue.
Necrosis
Refers to an area of necrosis in which the gross and microscopic architecture of the tissue and some of the cells are preserved. Presumably, the cell’s structural and enzymatic proteins are denatured and rendered insoluble soon after cell death; thus, autolysis or self-digestion is hindered.
Microscopically, tissue structures and cellular outlines are recognizable; nuclei are pyknotic or absent; the cytoplasm is strongly acidophilic and opaque.
Grossly, necrotic tissue is grey to white (unless filled with blood), firm, dense, and often depressed compared to surrounding normal tissue.
Coagulative necrosis
Coagulative necrosis is most commonly the result of: (4 answers)
- (1) sudden severe ischemia (infarcts),
- (2) certain acute acting toxins (mercury chloride, etc.),
- (3) toxin produced by certain bacteria (Fusiformis necrophorus) and
- (4) mild burns
The term ______ ______ refers to coagulation of proteins of sarcoplasm. The condition occurs only in striated muscle. Microscopically, individual fibers are swollen, homogeneous and hyaline in texture. The sarcoplasm is usually eosinophilic, the myofibrils are indistinct and the nuclei are pyknotic. Grossly, involved muscle fibers are pale, rather shiny, and swollen.
Zenker’s necrosis
Refers to an area of necrosis which disintegrates very rapidly into a liquid mass, resulting in a loss of cellular and architectural outlines.
Liquefactive necrosis
*** The very rapid liquefaction is due to autolysis (release of enzymes from the cell’s own lysosomes) and to heterolysis (lysosomal enzymes from invading neutrophils). In liquefactive necrosis, the dead cells are digested, creating a defect which is filled usually by invading neutrophils.
*** A tissue defect of this nature frequently occurs in nervous tissue soon after death due to the high content of lipid and small amounts of coagulable protein. Thus, there are two principal situations in which liquefactive necrosis occurs - abscesses found in any body site and in the central nervous system.
*** Pyogenic bacteria (staphylococci, streptococci, etc.) are usually the cause of abscesses. Microscopically, the necrotic area may appear as empty spaces with frayed and irregular edges (commonly observed in the central nervous system); or it may be represented by a dehydrated residue of neutrophils, tissue debris and fibrin.
Refers to a distinctive pattern of necrosis which is a combination of coagulative and liquefactive necrosis. The gross and microscopic architecture of the cells/tissue is lost, but the necrotic tissue is not completely liquified.
Caseous necrosis
*** Caseous necrosis is associated with diseases in which granulomatous lesions occur (tuberculosis, mycotic infections, etc.). The caseous material usually remains in place for prolonged periods of time and is prone to undergo calcification. Liquefaction and disappearance seldom occur.
*** Microscopically, the necrotic cells are not totally liquified nor are their outlines preserved, creating a distinctive amorphous granular debris.
*** The necrotic material is usually enclosed by a connective tissue capsule. Grossly, the necrotic tissue is soft to firm, dry, friable, grayish-white to yellow, and resembles “milk curds” or cottage cheese. The term “caseous” is derived from the gross appearance of the necrotic tissue (white and cheesy).
A distinctive type of necrosis involving adipose tissue. It occurs in the body cavities (especially the abdomen) and beneath the skin.
Fat necrosis
*** Enzymatic fat necrosis occurs subsequent to pancreatic damage and the release of activated pancreatic enzymes into the abdominal cavity. The activated lipases split the triglyceride esters of adipose tissue into fatty acids and glycerin. The fatty acids combine with metallic ions (calcium, potassium sodium, etc.) to form a soap within what was once a fat cell.
*** Microscopically, the fat within adipose tissue cells is replaced by a soap which is solid, opaque and nearly homogeneous. The necrotic fat cell takes a bluish to pinkish tinge, depending on the presence of sodium or potassium, respectively. It is purple if calcium is deposited.
*** Cholesterol clefts are often present. Remember, the soap formed within necrotic fat cells is not dissolved out (as is fat) by fat solvents used in sectioning techniques. Grossly, necrotic fat is opaque, whitish, firm, chalky and somewhat granular. Enzymatic fat necrosis is not a specific form of necrosis. The cellular changes are essentially liquefactive.
*** Traumatic fat necrosis occurs primarily in subcutaneous adipose tissue. It is associated with mechanical trauma and pressure. However, the exact etiologic mechanism has not been clearly elucidated. Apparently, there is local damage to fat cells due to trauma with the release of fatty acids.
Refers to an area of necrosis (usually coagulative) which is invaded by saprophytic and/or putrefactive bacteria
Gangrenous necrosis
*** Initially, the tissues undergo coagulative necrosis; subsequently, the coagulated tissues are invaded by saprophytic and/or putrefactive bacteria which attract neutrophils to the area; the liquefactive action of the bacteria and the lysosomal enzymes released by the invading neutrophils modify the coagulated tissue
The term commonly used when necrotic tissue is invaded by bacteria that produce large amounts of gas from constituents of the dead tissue.
Gas gangrene
Describe dry gangrene.
*** If the coagulative pattern is dominant, the process is called dry gangrene.
*** The affected tissue is cool, dry, pale, shriveled and leather-like. There is a sharp line of demarcation between normal and gangrenous tissue.
Describe moist/wet gangrene.
*** If the liquefactive pattern is more pronounced, it is designated as wet gangrene.
*** In moist gangrene, affected tissue is swollen, soft, pulpy, foul smelling and usually dark or black in color.
The term _____ _____ is used when calcium salts are deposited in dead or dying tissues.
Dystrophic calcification
The term _____ _____ is used to refer to the deposition of calcium salts in living tissues. It occurs subsequent to some derangement in calcium metabolism that results in hypercalcemia.
Metastatic calcification
Empty spaces left by crystals of cholesterol dissolved out by solvent used in the preparation of microscopic sections.
Cholesterol clefts
*** The cholesterol crystals are derived from the protoplasm of dead and/or dying cells. Thus, cholesterol clefts may be quite prominent in regions where there has been considerable necrosis of cells relatively rich in cholesterol. Microscopically, cleft-like empty spaces persist.
*** They occur in picket fence-like groups. In frozen sections, cholesterol crystals may be observed. These crystals are anisotropic or birefringent. Grossly, cholesterol crystals are not observed unless deposited in large amounts.
*** If visible, they appear as shiny, yellowish, granular or flaky material. Cholesterol clefts have no significance other than to indicate the presence of tissue damage or necrosis
Name this outcome of necrotic tissue:
This occurs when fluid accumulates faster than it is drained away by the blood and lymph streams.
Liquefaction by Autolysis and Heterolysis with the Formation of a Cyst-like Accumulation of Fluid
Name this outcome of necrotic tissue:
This occurs when pyogenic bacteria are present in the necrotic tissue. Pus is formed.
Liquefaction by Autolysis and Heterolysis with the Formation of Abscesses:
Name this outcome of necrotic tissue:
This may occur when there is very little moisture in a part and the inflammatory reaction is not intense enough to assist in the liquefaction of the necrotic mass.
Thus, within a few days, there is a proliferation of fibrous connective tissue around the necrotic tissue.
Eventually, _____ occurs. ______ caseous or coagulative necrotic tissue may persist in the body for a long time with little or not harm to the host.
Encapsulation without Liquefaction
Name this outcome of necrotic tissue:
This refers to the separation of necrotic tissue from viable tissue on an external or internal body surface (skin, intestine, etc.).
Desquamation or Sloughing of Necrotic Tissue
*** The term “desquamate” is used when thin layers of necrotic cells in the epithelial layer separate from the underlying viable tissue (the defect that remains is referred to as an erosion).
*** The term “sloughing” is used when larger masses of necrotic cells (extends beyond the surface epithelum) are separated from the underlying viable tissue (the defect that remains is referred to as an ulcer).
Name this outcome of necrotic tissue:
This occurs as a terminal stage. After necrotic tissue is removed, the damaged organ or part is restored as nearly as possible to its previous normal condition.
Regeneration of Replacement by Connective Tissue of Cells Lost via Necrosis
*** The term regeneration refers to the process whereby lost cells are replaced by others of the same kind (some cells regenerate readily whereas others do not).
*** In replacement by connective tissue or scar tissue formation, the lost cells are replaced by fibrous connective tissue.
Describe somatic death.
Refers to death of the entire body. The absence of heart beat, pulse, respiration, or brain waves have been used to define somatic death. In other words, somatic death is characterized by cessation of all organ function. It is quite difficult, however, to determine the precise moment at which somatic death occurs. In man, this difficulty assumes considerable medical, ethical and legal importance.
Refers to self-digestion by enzymes that are present within, or released into, the cytoplasm of cells after death.
Postmortem autolysis
Name this specific type of postmortem changes:
Refers to the decomposition of tissues by bacterial enzymes.
After death, bacteria from the digestive tract, etc., are able to invade, multiply and eventually digest tissues with their enzymes. Affected tissues are soft and foul-smelling.
Postmortem putrefaction
Name this specific type of postmortem changes:
Refers to the stiffening of all muscles after death. It is related to a progressive decrease in oxygen, ATP, creatinine phosphate and pH of muscles.
Rigor Mortis
*** Muscle fibers shorten as they pass into rigor. Rigor classically begins in one to six hours after death and disappears in 24-48 hours (as putrefaction begins).
*** However, it may be delayed or absent depending on various external factors. For example, rigor is enhanced by high metabolic activity and temperature prior to death. It is delayed by starvation, cachexia and cold.
*** Rigor mortis begins earliest in cardiac muscles. In skeletal muscles, rigor begins in the anterior portion of the body and progresses in a posterior direction (head, neck, trunk, limbs). Rigor disappears in the same order as it appears.
Name this specific type of postmortem changes:
Refers to the loss of body heat as the temperature of the body gradually equilibrates with its environment.
Algor Mortis
