This document discusses various patterns of tissue necrosis seen microscopically: - Coagulative necrosis preserves tissue architecture for days as cells are slowly removed by phagocytosis. It can result from ischemia. - Liquefactive necrosis digests dead cells into a liquid mass due to bacterial or fungal infection stimulating leukocytes. Pus results. - Specific types of necrosis include caseous, fat, fibrinoid, and those seen in conditions like gangrene and myocardial infarction.

4. Patterns of Tissue Necrosis
• When large numbers of cells
die the tissue or organ is
said to be necrotic
• thus, a myocardial infarct is
necrosis of a portion of the
heart caused by death of
many myocardial cells.

5. Patterns of Tissue Necrosis
Necrosis of tissues has several
morphologically distinct
patterns, which are important to
recognize because they may
provide clues about the
underlying cause.

6. Coagulative necrosis
• Form of necrosis in which the
architecture
• of dead tissues is preserved for a
span of at least some days .
• The affected tissues exhibit a firm
texture.
• Presumably, the injury denatures
not only structural proteins
•

7. • but also enzymes and so blocks the
proteolysis of the dead cells;
• as a result,eosinophilic,anucleate
cells may persist for days or weeks.
• Ultimately the necrotic cells are
removed by phagocytosis of the
cellular debris by infiltrating
leukocytes and
•

8. • by digestion of the dead cells by the
action of lysosomal enzymes of the
leukocytes.
• Ischemia caused by obstruction in a
vessel may lead to coagulative necrosis
of the supplied tissue in all organs
except the brain.
• A localized area of coagulative necrosis
is called an infarct.

13. Acute myocardial infarction

14. Liquefactive necrosis
• In contrast to coagulative necrosis, it is
characterized by digestion of the dead cells,
resulting in
• transformation of the tissue into a liquid viscous
mass. It is seen
• in focal bacterial or, occasionally, fungal infections,
because
• microbes stimulate the accumulation of leukocytes
and the liberation of enzymes from these cells.

15. Liquefactive necrosis
• The necrotic material is
• frequently creamy yellow because of the
presence of dead
• leukocytes and is called pus.
• For unknown reasons, hypoxic
• death of cells within the central nervous
system often manifests
• as liquefactive necrosis

18. Gangrenous necrosis
• is not a specific pattern of cell death,
• but the term is commonly used in
clinical practice.
• It is usually applied to a limb,
generally the lower leg, that has lost
its blood supply and has undergone
necrosis (typically coagulative
necrosis).

19. Gangrenous necrosis
• When bacterial infection is superimposed
there is more liquefactive necrosis
• because of the actions of degradative
enzymes in the bacteria
• and the attracted leukocytes (giving rise to
so-called wet gangrene).

21. Caseous necrosis
• Most often in foci of tuberculous infection
• The term “caseous” (cheese like)is derived from
the friable white appearance of the area of
necrosis
• On microscopic examination, the necrotic area
appears as a structureless collection of
fragmented or lysed cells and amorphous
granular debris enclosed within a distinctive
inflammatory border; this appearance is
• characteristic of a focus of inflammation known
as a granuloma

24. Fat necrosis
• Refers to focal areas of fat destruction,
typically resulting from release of
activated pancreatic lipases into the
substance of the pancreas and the
peritoneal cavity.
• In this disorder pancreatic enzymes
leak out of acinar cells and liquefy the
membranes of fat cells in the
peritoneum.

25. Fat necrosis
• 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

26. Fat necrosis. The
areas of white chalky
deposits represent
foci of fat necrosis
with calcium soap
formation
(saponification) at
sites of lipid
break down in the
mesentery.

27. Fibrinoid necrosis
is a special form of necrosis usually
seen in immune reactions involving
blood vessels. This pattern of
necrosis typically occurs when
complexes of antigens and antibodies
are deposited in the walls of arteries

28. Fibrinoid necrosis
• Deposits of these “immune
complexes,” together with fibrin that
has leaked out of vessels, result in a
bright pink and amorphous
appearance in H&E stains, called
“fibrinoid” (fibrin-like)

29. Fibrinoid necrosis in
an artery. The wall of
the artery shows a
circumferential
bright pink area of
necrosis with
inflammation
(neutrophils with
dark nuclei).

30. • A coronary angiogram of 53 years old male reveals
>90% occlusion of the left anterior descending artery. In
this setting, an irreversible injury to myocardial fibers
will have occurred.which of the following cellular
changes occurs?
• A Glycogen stores are depleted
• B Cytoplasmic sodium increases
• C Nuclei undergo karyorrhexis T
• D Intracellular pH diminishes
• E Blebs form on cell membranes

31. •C Nuclei undergo
karyorrhexis

32. • A 10-year-old black man with a known history
of sickle cell disease presents to the emergency
department complaining of left upper quadrant
pain suggestive of a splenic infarct. Microscopic
examination of the spleen would most likely
reveal
• A. Caseous necrosis
• B. Coagulative necrosis
• C. Fibrinoid necrosis
• D. Gangrenous necrosis
• E. Liquefactive necrosis

33. •B. Coagulative
necrosis

34. • A circumscribed mass of light yellow
crumbly to pasty material associated
microscopically with a macrophage
response is characteristic of
• A. Caseous necrosis
• B. Coagulative necrosis
• C. Fibrinoid necrosis
• D. Gangrenous necrosis

35. •A. Caseous necrosis

38. Mechanisms of Cell Injury

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