irreversibile cell injury and cell death

what is the "point of no return"?

it is the point where the injury to the cell is no longer reversible, and will lead to cell death

irreversible cell injury leads to....

cell death

what are the 2 types of cell death?

1. death by swelling- necrosis/oncosis

2. death by shrinking- apoptosis

death of a cell by swelling is called....

necrosis/oncosis

death of a cell by shrinking is called....

apoptosis

what is the difference between necrosis and autolysis?

necrosis is pathological and is the death of living cells

autolysis is physiological, and is the post-mortem degeneration of cells

autolysed organs appear....

shrunken

what are the possible ways that the nucleus can change after cell death?

-pyknosis: shrunken, dark, homogenous, round

-karyorrhexis: ruptured, dark fragments in cytoplasm

-karyolysis: pale due to dissolution of chromatin

-absence of nucleus: later stage of karyolysis

what is pyknosis?

the condensation of chromatin in the nucleus of a cell due to cell death. the nucleus appears shrunken, dark, homogenous, and round

what is karyorrhexis?

the fragmentation of the chromatin after cell death. the cell has fragments irregularly floating within the cytoplasm

what is karyolysis?

the dissolution of chromatin after cell death. the nucleus is pale and will disappear completely

what are the 2 instances that tell us the cell has reached a point of no return?

1. inability to restore mitochondrial function

2. obvious cell membrane damage

if an injured cell cannot restore mitochondrial function and has obvious cell membrane damage, we say that it has reached the ...

point of no return

what are the effects of free radicals?

-peroxidation of membrane lipids

-oxidative changes of proteins

-DNA damage

what occurs when a cell has obvious membrane damage?

there will be an influx of Ca2+, which activates enzymes (ATPases, endogenous phospholipases, proteates, endonucleases), including arachidonic, acid, which attracts an immune response, causing inflammation

what are the causes of coagulative necrosis?

hypoxia, ischemia, toxins

describe coagulative necrosis

necrosis caused by ischemia, hypoxia, or toxins, where the organ and cell structures are preserved by coagulation of proteins. the color and texture changes, but the structure stays the same. proteins are denatured.

the necrotic tissue will be phagocytized and lysed in a few days, and a scar will replace the dead tissue

which type of necrosis leaves the tissue structure completely normal?

coagulative necrosis

in coagulative necrosis, proteins are denatured, which causes what microscopic appearance?

pyknotic, karyorrhetic, or absent nucleus

eosinophilic cytoplasm

what is the consequence of a tissue that has died by coagulative necrosis?

it will be phagocytized and lysed in a few days, with a scar replacing the dead tissue. the animal can survive.

coagulative necrosis is typical in what organs?

liver, kidney, muscle

it can be found anywhere, except nervous tissue

caseous necrosis is typical of what disease?

tuberculosis

what type of necrosis leaves the tissue granular and friable?

caseous necrosis

which is more chronic- coagulative or caseous necrosis?

caseous

caseous necrosis is common in what tissues?

lungs, lymph nodes

can be seen in any tissue

can any tissue undergo coagulative necrosis?

no- nervous tissue cannot

can any tissue undergo caseous necrosis?

yes

how does a tissue that underwent caseous necrosis appear?

grossly:

surrounded by an external fibrous capsule

yellow

sometimes hard

microscopically:

foci of nuclear and cytoplasmic remains

dead leukocytes

which type of necrosis leaves the tissue with a cheese-like appearance?

caseous necrosis

what type of necrosis does this describe:

In the development of this lesion, bacteria wall degradation plays a key role, causing a foci of _________ necrosis, surrounded by granulomatous inflammatory cells and a external capsule of fibrous tissue

caseous necrosis

how does a caseous necrosis lesion change over time?

more immune cells are recruited and die, causing growth of the tissue. the tissue also hardens because it accumulates calcium ("dystrophic calcification")

in the CNS, what type of necrosis will be observed due to hypoxia?

liquefactive necrosis

in the CNS, what is the cause of liquefactive necrosis?

hypoxia

what happens to the tissue that dies by liquefactive necrosis?

in the CNS, the spaces that are left will fill with lipidic remains and fluids

in other tissues, it will become an abscess, which can even become caseous if the liquid is lost or hardens

what is the cause of liquefactive necrosis?

pyogenic bacteria infection

OR if it is in the brain, hypoxia

pyogenic bacteria infections can cause ______ necrosis

liquefactive

what is wet gangrene?

lesion produced when a tissue with coagulative necrosis is further degraded by saprophytic bacteria that have contaminated it from the environment. the bacteria cause putrifaction of the tissue, leaving a soft, moist, red-brown-black tissue.

when saprophytic bacteria infect a tissue that already has coagulative necrosis, this produces _______

wet gangrene

what is the appearance of a tissue with wet gangrene?

soft, moist, red-brown to black, sometimes with gas bubbles

what is the danger of wet gangrene?

it can spread to other parts of the body if it is not separated.

we must remove the necrotic tissue and clamp it to prevent the spread of the toxins into the blood.

dry gangrene results from.....

loss of blood flow to a specific part of the body, caused by toxins or cold. the tissue will mummify/solidify.

which type of gangrene is produced by the effect of bacteria?

wet gangrene

gas gangrene

how does dry gangrene appear?

shriveled, dry, brown-black

what is the cause of dry gangrene?

loss of blood flow to a specific part of the body due to toxins or cold

some toxins cause vessel constriction, leading to lack of blood flow

intense cold can cause freezing and cell damage by forming crystals

in what type of gangrene are the tissues depleted of water?

dry gangrene

what causes gas gangrene?

gas-producing (anaerobic) bacteria infecting necrotic tissue

when gas-producing (anaerobic) bacteria infects necrotic tissue, what is the result?

gas gangrene

how does gas gangrene appear?

grossly:

dark red-black

gas bubbles and fluid

microscopically:

coagulative necrosis

serohemorrhagic exudate

gas bubbles

in which organ is fat necrosis the most common?

pancreas- due to pancreatic lipases

what are the 2 types of fat necrosis?

1. traumatic fat necrosis- this is where adipose tissue is crushed (common in pelvic fat and subcutanenous tissue)

2. abdominal fat necrosis- this occurs in cattle, the cause is unknown. in the mesentery, omentum, and retroperitoneum. can cause intestinal stenosis if it involves fat surrounding the intestines.

traumatic fat necrosis is common where in the body?

pelvic fat

subcutaneous tissue

how does fat necrosis appear?

grossly:

dry, salty

microscopically:

if there is saponification, necrotic adipocytes are basophilic

what type of necrosis has a dry and salty appearance?

fat necrosis

what are the consequences of necrosis?

inflammation

irritation and sequestrum if it cannot be degraded