Irreversible Cell Injury 3 - Necrosis

Question 1

5 types of necrosis

Answer 1

1. Coagulative necrosis
2. Liquefactive necrosis
3. Caseous necrosis
4. Gangrenous necrosis
5. Enzymatic necrosis

Question 2

-Coagulative necrosis
-_________ induced in what organs
-basic tissue preserved or not?

Answer 2

Ischaemia/toxin in liver, heart, kidney, skeletal muscle
Preserved temporarily

Question 3

Liquefactive necrosis
____________ induced in CNS

Answer 3

Ischaemia/toxin

Question 4

Caseous necrosis
Caused by…
Causes…

Answer 4

Mycobacteria infections like Tuberculosis
Causes tissues to become “cheese-like” in appearance

Question 5

What changes do we recognise with cell death under the microscope?

Answer 5

—cytoplasmic changes
—nuclear changes

Question 6

Cytoplasmic changes in the morphology of cell death
—early phase

Answer 6

Early phase:
-Cytoplasm becomes homogeneous pink in H&E section
Increased eosinophilia due to: loss of RNA which is responsible for cytoplasmic basophilia so basophilia lost
-condensed cytoplasm
-degradation of cytoplasmic proteins causes ghost-like appearance
-necrotic cells become “ individualised” i.e lose adherence/attachment to basement membranes and adjacent cells

Question 7

Cytoplasmic changes in the morphology of cell death

—late phase

Answer 7

Cell membrane rupture with loss of integrity and release of cell contents into extracellular space

Question 8

Name the 4 Nucleur changes in morphology of cell death

Answer 8

-Pyknosis
-Karyorrhexis
-Karyolysis
-Absence

Question 9

Describe nuclear change of Pyknosis in cell

Answer 9

Shrunken, dark, homogenous, round, basophilic nuclei

Question 10

Describe nuclear change of Karyorrhexis of cell

Answer 10

Fragmentation of nucleus
-rupture of nuclear membrane and chromatin
-dark nuclear remnants released into cytoplasm

Question 11

Describe nuclear change of Karyolysis of cell

Answer 11

Nucleus becomes very pale
-due to dissolution of chromatin by DNAses

Question 12

Describe the nuclear change of Absence of cells nucleus

Answer 12

Completely dissolved or lysed nucleus

Question 13

Diagram of the different nuclear changes of cell during cell death

Answer 13

https://www.google.co.uk/url?sa=i&url=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FKaryolysis&psig=AOvVaw01aar9gkKfkmEcpPTUQp2I&ust=1674673524348000&source=images&cd=vfe&ved=0CA8QjRxqFwoTCMDljpbz4PwCFQAAAAAdAAAAABAg

https://www.google.co.uk/imgres?imgurl=https%3A%2F%2Fi0.wp.com%2Fwww.pathologystudent.com%2Fwp-content%2Fuploads%2F2022%2F08%2FNuclear-changes.png%3Fresize%3D655%252C212%26ssl%3D1&imgrefurl=https%3A%2F%2Fwww.pathologystudent.com%2Fdoes-pyknosis-occur-in-necrosis-or-apoptosis%2F&tbnid=x82gbgAnzZirHM&vet=12ahUKEwiWgc7R8-D8AhWOsCcCHZDuBgIQMygDegUIARDBAQ..i&docid=6Lgk51fnFeGPWM&w=655&h=212&q=pyknosis%2C%20karyohsis%20and%20karyolitic%20cell%20diagrams&hl=en-gb&client=safari&ved=2ahUKEwiWgc7R8-D8AhWOsCcCHZDuBgIQMygDegUIARDBAQ

Question 14

Common causes of Coagulative necrosis

Answer 14

Hypoxia- local loss of blood supply
Ischaemia
Bacterial or chemical toxins
Local actin of irritating substances

Question 15

Causes for renal necrosis (kidney)

Answer 15

Plants—>
—Cattle: -oak, acorn
-Oxalate (rhubarb, sorrel, dock)
—Cats:- Easter lily
—Pigs:- redroot pigweed phenolic compounds)
—Dogs:- raisins/grapes

Heavy metals—> mercury, lead

Chemicals—> ethylene glycol

Therapeutic drugs—-> antibiotics & chemotherapeutics

Question 16

Necrosis relating to infectious disease
-viral infections
-bacterial infections

Answer 16

Viral infections

Infectious Bovine Rhinotracheitis (IBR)
-Bovine Herpesvirus 1 (BHV-1)
Canine parvoviral enteritis
-Canine Parvovirus 2 (CPV-2)
Canine infectious hepatitis
-Canine Adenovirus 1 (CAV-1)

Bacterial infections

Tuberculosis (Mycobacteria)
-Mycobacterium tuberculosis, M. bovis, other
Salmonellosis (S. enterica, serotypes S. typhimurium, S. choleraesuis, S. dublin etc.)
Clostridial infections (Cl. perfringens, Cl. difficile, Cl. chauvoei, Cl. septicum, other…)

Question 17

Infectious Bovine Rhinotracheitis
-caused by…
-causes what?
-may also cause secondary bacterial infection which results in…

Answer 17

-Bovine Herpesvirus 1

-causes transient acute febrile illness with respiratory signs
-causes severe hyperaemia and focal necrosis of: trachea, larynx, nasal cavity pharynx and mucosae

-also may cause secondary bacterial infection which results in thick plaques of fibrinonecrotic exudate

Question 18

Canine parvovirus enteritis
-caused by what
-causes what

Answer 18

-caused by canine parvovirus-2
-causes segmental necrosis and haemorrhage of small intestine (with this might also see variable dilation of intestinal loops &
granular texture of serosal surface)

Question 19

Canine infectious hepatitis
-caused by what
-causes what

Answer 19

Caused by CAV1
Causes liver to be enlarged and friable; will see fibrin on capsular surface and over liver lobes. Liver has granular appearance on serosal surface. Gallbladder walls thickened by oedema

Question 20

Caseous necrosis
-what does dead tissue look like
-microscopic appearance;
-contains what
-examples

Answer 20

Dead tissue converted into a glandular, friable mass
-Resembles cottage cheese
● Microscopic appearance
– accumulation of fragmented / lysed cells with an amorphous granular appearance
– tissue architecture obliterated, no cell outlines visible
– dystrophic calcification often seen centrally
● Chronic lesions
– often associated with poorly degradable bacterial lipids
Classic examples
– TUBERCULOSIS
– Corynebacterium pseudotuberculosis in sheep

Question 21

Caseous lymphadenitis (CLA)
-in which animals
-causes
-caused by
-spread by…
-incubation period

Answer 21

Sheep/goats
-causes chronic suppurative lymphadenitis
-caused by Corynebacterium pseudotuberculosis
-spread by;
● Shearing wounds
– arthropod bites or contaminated dips
● Spread by ruptured abscesses, oral and nasal secretions
Incubation period; 3 months

Question 22

Liquefactive necrosis

Answer 22

-Specific for CNS
-caused by hypoxia or toxin induced by neuronal necrosis which causes liquefaction

Question 23

What is liquefaction?

Answer 23

partial or complete dissolution of dead tissue and transformation into a liquid, viscous mass

Question 24

Describe the process of Liquefactive necrosis occurring due to pyogenic bacteria

Answer 24

1.Recruitment of inflammatory cells (mainly neutrophils)

2.Release of lytic enzymes

3.Destruction of bacteria
+ degeneration & necrosis of neutrophils

4.ABSCESS (pus-filled cavity)
can be considered a type of liquefactive necrosis

Question 25

3 types of gangrenous necrosis

Answer 25

-Moist
-Dry
-Gas

Question 26

Moist gangrenous necrosis
-Caused by…
-Requires which type of bacteria to occur?

Answer 26

-Infarction
-ischaemic necrosis in extreme cases
-Liquefactive action of saprophytic bacteria (requires this bacteria)

Question 27

Moist gangrenous necrosis
-gross findings
-histological findings

Answer 27

Gross: Soft, moist, reddish-brown-black,
Variable gas bubbles, putrid smell

Histological: Coagulative necrosis + proliferating bacteria,
Liquefaction +/- gas bubbles

Question 28

Dry gangrene necrosis

Answer 28

Coagulation necrosis secondary to infarction with mummification (dehydration)
-occurs normally in the distal limbs, tails, ears, udder
-related to ingestion of toxins, or cold (frostbite)
-gross appearance: dry, black/brown

Question 29

Gas gangrene necrosis (malignant oedema)
-caused by…
-gross & microscopic appearance

Answer 29

-Caused by infections with anaerobic bacteria that are proliferating & producing toxins in tissues - bacteria introduced by penetrating wounds into muscle/subcutis

-tissue is dark red to black
-sero-haemorrhagic exudate
-gas bubble formation
-coagulation necrosis of muscle

Question 30

How are anaerobic bacteria introduced into cell during gas gangrene

Answer 30

By penetrating wounds into muscle/subcutis

Question 31

Example of gas gangrene necrosis

Answer 31

Blackleg caused by clostridium chauvoei

Question 32

Describe the process of Blackleg Gas gangrene ad how it reaches bacterial proliferation/toxin production

Answer 32

● Bacteria not introduced with a penetrating wound
● Spores spread haematogenously from the intestine & lodge into muscles (and remain latent) until local tissue trauma with hypoxia occur—> anaerobic conditions—>spores germinate—> bacterial proliferation
& toxins production/release

Question 33

Fat necrosis

Answer 33

Enzymatic- release of activated pancreatic lipases—>destruction of pancreatic adipose tissue
Traumatic- commonly caused by trauma; crushed fat
Idiopathic- abdominal fat necrosis of cattle

Question 34

3 Consequences of necrosis

Answer 34

● Inflammatory reaction within viable tissue – band of white blood cells
– hyperaemia
● Digestion and liquefaction of necrotic tissue – Phagocytosis (removal) by macrophages
– drainage through blood/lymphatic vessels
● Regeneration of normal tissue or fibrous scarring