Pathology Necrosis 2

Front 1

What is physiologic cell death?

Back 1

death of a cell at the end of it

Front 2

What is pathologic cell death?

Back 2

1. death before the end of its normal life span.
2. result of irreversible cell injury

Front 3

Define necrosis

Back 3

Morphologic changes that follow cell death in a living animal, resulting from progressive, degradative action of enzymes on the cell.

Front 4

Define autolysis

Back 4

"dead cell in dead body or dead cell in living body"
1) degradative changes in a cell due to action of endogenous enzymes, primarily from lysosomes
2) see in postmortem autolysis or decomposition
3) seen with necrosis and physiologic cell death.

Front 5

Define fixation

Back 5

1. rapid killing of cells by denaturing proteins to prevent autolysis and preserve architecture.
2. commonly use 10% neutral-buffered formalin (buffer prevents decrease in pH and formation of acid hematin deposits, which are products of acid + hemoglobin)

Front 6

Name 4 nuclear changes following cell death.

Back 6

1. pyknosis --> nucleus small, densely basophilic, round, homogeneous; common
2. karyorrhexis --> nucleus breaks up into smaller fragments, +/- scattered in cytoplasm; common
3. karyolysis --> progressive loss of chromatin staining, chromatin dissovles but nuclear membrane may remain as a "ghost", presumable due to DNase; occasionally seen
4. Absence of nucleus

Front 7

Name 3 cytoplasmic changes following cell death.

Back 7

1. Acidophilia (eosinophilia)
a. common
b. cytoplasm stains an intense pink or red
c. due to loss of ribonucleic acids that normally stain basophilic
d. due to increased binding of acidic dye to denatured proteins
2. lysis
a. common; pale pink staining, vacuolation; due to loss of proteins and digestion of organelles
3. calcification - fine basophilic dots

Front 8

Name 3 "advanced" changes following cell death.

Back 8

1. loss of cell line: indistince cell borders; cell membrane partially or completely gone
2. loss of differential staining: lack of normal differences in staining between parts of cells and different types of cells
3. absence of cells: cells not present where they should be, assume death and removal of debris.

Front 9

Name 3 gross features of necrotic tissue.

Back 9

1. color changes
a. pallor diffuse or patchy; due to cell swelling, loss of blood
b. Dark red, brown or black - diffuse or patchy; due to blood (hyperemia, hemorrhage or hemolysis)
2. Loss of strength
a. tissue soft due to hydrolytic enzymes +/- bacteria
b. friable; malacia (softening of neural tissue)
3. odor: foul odor if putrefactive bacteria present.

Front 10

Name 8 possible sequelae to necrosis.

Back 10

1. death due to organ dysfxn or to toxemia
2. inflammation
3. liguefaction: liquefied due to hydrolytic enzymes from tissue and/or PMNs
4. Encapsulation: necrotic tissue isolated from adj. viable tissue by fibrous connective tissue wall.
5. sequestration: necrotic tissue becomes isolated from circulation of viable tissue and persists for a long time.
6. sloughing: separation of necrotic tissue from viable tissue
a. ulcer-surface excavation due to slughing of necrotic tissue; necrosis extends below the basal layer of epithelium
7. mineralization
8. Healing
a. necrotic tissue removed and replaced
b. outcome depends on type of tissue and extent of injury
c. regeneration: parenchymal replacement
d. scarring: replace with fibrous connective tissue or glial cells (CNS)

Front 11

list 2 factors that affects the rate of postmortem autolysis.

Back 11

1. Temperature: accelerated by increased temperature due to environment, fever, slow dissipation of heat (sheep)
2. Tissue variation: a) high metabolic activity; b) presence of endogenous hydrolytic enzymes (int, panc)

Front 12

What are some of the microscopic alterations associated with postmortem autolysis?

Back 12

a. hemolysis of red blood cells (appear faint pink or orange, with indinstinct margins
b. uniform loss of differential staining in a tissue section
c. bacilli in blood vessels and tissues w/o inflammation
d. gas bubbles from putrefactive bacteria
e. desquamation of endothelium and epithelium
f. individualization of cells due to loss of cellular jxn
g. microscopic changes of cell death (a. presence of "dead" and "living" tissue in same section suggest necrosis. b. presence of inflammatory cells and hyperemia around "dead" tissue indicates necrosis)

Front 13

What are some of the gross alteration associated with postmortem autolysis?

Back 13

1. postmortem tympanites (a. distension of GI tract due to gas-producing bacteria; b. +/- prolapses or rupture of a hollow organ)
2. postmortem emphysema (gas pockets in tissues other than gut, esp in liver, spleen, and subcutis, due to gas producing, PM bacilli
3. epithelial desquamation (rumen)
4. Friable (hydrolytic enzymes + bact prod)
5. muscle color (pale red to pink, soft & watery)
6. imbibition
7. Rigor mortis
8. Livor mortis (hypostatic congestion)
9. algor mortis (cooling of body after death)

Front 14

Rigor mortis

Back 14

a. stiffening of muscles after death
b. due to release of Ca and decreased ATP --> muscle contraction
c. onset variable (1-6 hrs) and lasts 24-72 hrs
d. influenced by pH, temp, nutritional status

Front 15

List 5 types of necrosis.

Back 15

1. coagulative necrosis
a. zenker's necrosis
b. infarct
2. Liquefactive necrosis
3. caseous necrosis
4. gangrenous necrosis
5. fat necrosis

Front 16

coagulative necrosis

Back 16

represents cell death in which the gross and microscopic architecture of the tissue is still recognizable. it is presumably due to denaturation of structural and enzymic proteins.

Front 17

When does coagulative necrosis occur?

Back 17

1. acute anoxia (e.g. ischemia)
2. acute toxic injury
3. certain bacterial & viral agents

Front 18

Whats the gross appearance associated with coagulative necrosis?

Back 18

1. pallor, tan to white to yellow
2. firm, but friable

Front 19

What are the microscopic appearance associated with coagulative necrosis?

Back 19

1. outline of cells and architecture of tissue remains
2. cytoplasm eosinophilic
3. nuclear pyknosis, karyorrhexis, karyolysis or absence
4. dead cells appear as "shadows" or "ghosts"
5. inflammatory changes (hyperemia, leukocytes, edema) or degenerative changes (hydropic, fatty) esp. at periphery of necrotic tissue

Front 20

Infarct

Back 20

a. localized area of coagulative necrosis due to reduce blood supply
b. gross appearance: pale white to tan or red, well-demarcated from variable tissue, often wedge-shaped.
c. sequelae: death due to organ dysfxn, toxemia; scarring

Front 21

Zenker's necrosis

Back 21

a. coagulative necrosis of striated muscle
b. causes: plant toxins; bacteria; vitamin E-Se deficiency; exertional myopathy; ischemia
c. Gross appearance: pale areas and/or streaking; +/- swollen
d. Sequelae: regeneration (skeletal muscle); scarring (cardiac & skeletal muscles)

Front 22

Whats the microscopic appearance for Zenker's necrosis?

Back 22

a. sequential changes: loss of striation --> fiber swelling --> coagulation of sarcoplasm (increased eosinophilia) --> fragmentation & clumping of cytoplasm --> infiltration of macrophages
b. mineralization of mitochondria - fine basophilic stippling of cytoplasm
c. healing-regeneration or scarring

Front 23

Liquefactive Necrosis

Back 23

Necrosis characterized by tissue that has liquefied due to the action of hydrolytic enzymes, primarily from neutrophils.

Front 24

When does liquefactive necrosis occur?

Back 24

1. abscess: occurs everywhere; a localized collection of pus; elicited by certain bacterial agents that attract neutrophils
2. CNS: tissue lacks protein--> no coagulation

Front 25

What are some of the gross appearance associated with liquefactive necrosis?

Back 25

1. Abscess
a. microscopic to large
b. well-circumscribed
c. +/- fibrous capsule
d. center filled with pus
e. +/- foul odor
2. CNS
a. malacia
b. +/- depressed
c. yellow to brown
d. cavitation (fluid filled space, with soft frayed edges)

Front 26

What are some of the microscopic appearance associated with liquefactive necrosis?

Back 26

1. Abscess
a. large numbers of PMN plus necrosis of parenchyma
b. fibrous capsule, mineralized debris in older lesions
2. CNS
a. decreased density of tissue, pale eosinophilia, poorly defined edges
b. +/- phagocytic cells (gitter cells)
c. may be cavity filled with eosinophilic, homogeneous material (percipitated protein) +/- Gitter cells, poorly defined edges.

Front 27

Whats the sequelae for liquefactive necrosis?

Back 27

1. abscess
a. pyemia: abscess --> bacterial emboli spread via blood --> disseminated abscesses --> +/- death due to septicemia
b. septicemia- bacteria plus bacterial toxins in the blood, can cause hemodynamic changes and/or cell injury
c. resolution: abscess walled off --> resorption of debris +/- mmineralization --> scar
2. CNS
a. removal of debris by phagocytes
b. healing by gliosis - proliferation of fibrillar astrocytes, NOT fibrocytes
c. loss of fxn - sings attributed to areas affected.

Front 28

Gangrenous Necrosis

Back 28

negrosis represents ischemic injury modified to varying degrees by exposure to air or by the liquefactive action of bacteria. in some cases, the lesions are a combination of coagulative necrosis due to ischemia plus liquefaction due to bacterial or leukocytic enzymes.

Front 29

What is the occurrence for gangrenous necrosis?

Back 29

1. External - extremities, such as limbs, ears, combs
2. internal - lungs, intestine

Front 30

What are some of the causes for gangrenous necrosis?

Back 30

1. ischemia: thrombus, embolus, torsion, volvulus, chronic vasoconstriction, mechanical compression, freezing.
2. aspiration pneumonia due to inhalation of irritating gastric contents and GI bacteria
3. bacterial toxins-especially in mastitis

Front 31

what are some of the gross appearance associated with gangrenous necrosis?

Back 31

1. Dry gangrene
a. see in external locations (areas with limited circulation and where moisture from necrotic tissue can evaporate
b. gross appearance is more like coagulative necrosis
c. area dry, shriveled, leathery, dark red to black
d. cold, lacks sensation
e. red line of demarcation between necrotic and viable tissue
2. moist gangrene
a. see in internal organs & mammary gland (areas where blood vessels are abundant)
b. gross appearance is more like liquefactive necrosis
c. tissue dark red to black
d. soft, moist, friable
e. foul odor
f. +/- gass bubbles, crepitant on palpation
g. line of demarcation

Front 32

What are some of the microscopic appearance associated with gangrenous necrosis?

Back 32

1. dry gangrene
a. coagulative necrosis +/- bacteria
b. line of demarcation = leukocytes +/- bacT
2. moist gangrene
a. Coagulative + liquefactive necrosis +/- bacT
b. +/- gas bubbles
c. line of demarcation

Front 33

what are the sequelae for gangrenous necrosis?

Back 33

1. death - due to toxemia
2. sloughing

Front 34

Caseous Necrosis

Back 34

necrosis that is characteristic of certain bacterial infections and has a distinct appearance.

Front 35

Whats the occurrence for caseous necrosis?

Back 35

1. in any tissue
2. mycobacterium bovis
3. Corynebacterium pseudotuberculosis

Front 36

What are some of the gross appearances associated with caseous necrosis?

Back 36

1. localized, well demarcated lesion
2. soft, friable, grey-white material resembling coagulated protein
3. dry and crumbly or soft and pasty
4. +/- gritty on cutting due to mineralization
5. +/- laminated on cross-section

Front 37

What are the microscopic appearance for caseous necrosis?

Back 37

1. center of lesion w/o cell or tissue architecture
2. center with granular, eosinophilic debris, basophilic nuclear remnants, basophilic mineral
3. periphery with macrophages, other inflammatory cells, +/- multinucleated giant cells, +/- fibrous connective tissue.

Front 38

What are the sequelae for caseous necrosis?

Back 38

1. encapsulation and persistence for long time
2. healing by scarring.

Front 39

Fat Necrosis

Back 39

necrosis that represents necrosis of adipose tissue due to action of lipases. (involvement of SQ fat and/or sesenteric fat)

Front 40

What are the causes for fat necrosis?

Back 40

1. pancreatitis
necrosis of pancreatic acinar cells --> release of digestive enzyme into interstitium --> action of lipase and lecithinase on adjacent fat --> fat necrosis
2. diets high in polyunsaturated fats + decreased vit. E.
3. Trauma
4. idiopathic

Front 41

what are the gross appearance for fat necrosis?

Back 41

1. mesenteric fat - opaque, white, firm to hard, granular, gritty on cutting
2. SQ fat - opaque, yellow to brown (due to ceroid pigment), firm, lumpy

Front 42

What are the microscopic appearance for fat necrosis?

Back 42

1. outline of adipocytes may be present
2. fat replaeced with amorphous to granular material with variable staining
a. material represents fatty acid soaps: triglycerides --> glycerol + FA + cations --> soaps stain pink, blue, purple, respectively
3. inflammation - PMNs, macrophages, multinucleated giant cells
4. fibrosis
5. +/- fatty acid crystals - fine, needle-like, clear spaces
6. +/- cholesterol crystals - larger, elongate, clear spaces.

Front 43

What are the sequelae for fat necrosis?

Back 43

1. incidental finding
2. with pancreatitis - death due to shock
3. scarring
4. interference with organ fxn