Cell Death

Question 1

Coagulative necrosis

Answer 1

The commonest type, occurs in most organs
Tissue is initially firm, later becomes soft as tissue is digested by macrophages
In the early phases the histological appearances may demonstrate little change
In later stages cellular outlines are seen with loss of intracellular detail

Question 2

Colliquative necrosis

Answer 2

Occurs in tissues with no supporting stroma
Dominant necrosis pattern in the CNS
Necrotic site may eventually become encysted

Question 3

Caseous necrosis

Answer 3

No definable structure seen in the necrotic tissue
Amorphous eosinophilic tissue may be seen histologically
Classically seen in tuberculosis

Question 4

Gangrene

Answer 4

Necrosis with putrefaction of tissue
May complicate ischaemia
Haemoglobin degenerates and results in the deposition of iron sulphide (which is why the tissue is black)
Both wet and dry gangrene may occur, in wet gangrene there is often a liquefactive component and super-added infection (which usually smells!)

Question 5

Fibrinoid necrosis

Answer 5

Classically seen in arterioles in patients with hypertension (malignant type)
Necrosis of the smooth muscle wall occurs and plasma may extravasate into the media with fibrin deposition

Question 6

Fat necrosis

Answer 6

Direct trauma to fat can result in rupture of adipocytes
Lipids incite a local inflammatory reaction
Inflammatory cells phagocytose the lipid with eventual fibrosis

Question 7

Apoptosis

Answer 7

Also known as programmed cell death
Energy dependent pathways are activated via a number of intracellular signalling mechanisms
It is the result of the activation of caspases triggered by the bcl-2 family or the binding of the FAS ligand to its receptor
DNA fragments, mitochondrial function ceases, nuclear and cellular shrinkage occurs
Phagocytosis of the cell does not occur, instead the cell degenerates into apoptotic bodies