CELL DEATH - NECROSIS

Question 1

Describe the morphology of Cell Injury

Answer 1

1- The changes are produced by enzymatic
digestion of dead cellular elements, denatunation of proteins and autolysis (by lysosomal enzymes)
2- Cytoplasm -­ increased eosinophilia
3- myelin figures -­ large, phospholipid masses derived from damaged cell membranes.
4- Nucleus -­ nonspecific breakdown of DNA leading to:
• pyknosis (shrinkage)
• karyolysis (fading) and
• karyorrhexis (fragmentation)

Question 2

What are the different patterns of necrosis?

Answer 2

• Coagulative -­ hypoxic death (except brain)
the outline of the dead cells are maintained and the tissue is somewhat firm
• Liquefactive -­ bacterial infections;; also hypoxic death in brain tissue (infarction) the dead cells undergo disintegration and affected tissue is liquified.
• Caseous -­ tuberculosis
• Fat -­ enzymatic or traumatic damage to fatty tissue;; eg.
Pancreatitis (enzymatic)
• Gangrenous -­ usually involves lower extremities and often is a type of coagulative necrosis
• Fibrinoid -­ immune complexes in arteries

Question 3

What is coagulative necrosis?

Answer 3

injured myocardium
• tissue is not recognizable
• nuclei:
pyknotic (shrunken and dark)
karorrhexis (fragmentation)
karyolysis (dissolution)
• cytoplasm and cell borders are
not recognizable.

Question 4

What is liquefactive necrosis?

Answer 4

This is liquefactive necrosis in
the brain in a patient who
suffered a "stroke" with focal
loss of blood supply to a
portion of cerebrum. This type
of infarction is marked by loss
of neurons and neuroglial cells
and the formation of a clear
space at the centre left.

Question 5

What is Caseous Necrosis?

Answer 5

Specific form of coagulation
necrosis typically caused by
mycobacteria (e.g.
tuberculosis)

It means cheese-­like

Example: tuberculosis lesions

Microscopically, caseous
necrosis is characterized by
acellular pink areas of
necrosis, as seen here at the
upper right, surrounded by a
granulomatous inflammatory
process

Question 6

What is fat necrosis?

Answer 6

Enzymatic digestion of fat

Example: necrosis of fat by
pancreatic enzymes.

Cellular injury to the pancreatic
acini leads to release of powerful
enzymes which damage fat by the
production of soaps, and these
appear grossly as the soft, white
areas seen here on the cut
surfaces.

Question 7

What is gangrenous necrosis?

Answer 7

Necrosis (secondary to ischemia) usually with superimposed infection. Example: necrosis of distal limbs, usually foot and toes in diabetes. In this case, the toes were involved in a frostbite injury. This is an example of “dry” gangrene in which there is mainly coagulative necrosis from the anoxic injury.

Question 8

What is fibrinoid necrosis?

Answer 8

Caused by immune-­‐ mediated vascular damage. It is marked by deposition of fibrin-­‐like proteinaceous material in arterial walls, which appears smudgy and
eosinophilic on light microscopy.