Solved Past Paper of General Pathology SEQs with Answers and Explanations

Questions regarding necrosis.
a) Define necrosis.
b) Enumerate its types. Give example of each
c) Which type is the most common and name the organ affected by it?
d) What are the morphological features of a necrotic cell?
e) Define the nuclear changes seen in necrotic cell nuclei
f) Write the morphology of each type of necrosis

a) DEFINITION:
Necrosis is the type of cell death that is associated with loss of membrane integrity and leakage of cellular contents, largely resulting from the degradative action of enzymes on lethally injured cells. The leaked cellular contents often elicit a local host reaction, called inflammation that attempts to eliminate the dead cells. The enzymes responsible for digestion of the cell may be derived from the lysosomes of the dying cells and lysosomes of leukocytes that are recruited in inflammatory response.

b) TYPES OF NECROSIS:
1) Coagulative necrosis, solid organs heart kidney
2) Liquefactive necrosis, central nervous Brain
3) Gangrenous necrosis, lower leg, abdominal viscera
4) Caseous necrosis, tuberculous infection i.e. lungs
5) Fat necrosis, pancreas (may be traumatic or enzymatic)
6) Fibrinoid necrosis, blood vessels wall.
c) MOST COMMON TYPE AND THE ORGAN AFFECTED BY IT:
Coagulative necrosis is the most common type of necrosis and the most affected organs are the solid organs except the brain.
d) MORPHOLOGICAL FEATURES OF A NECROTIC CELL

i) Cytoplasmic changes.
1) Necrotic cells show increased eosinophilia (i.e., pink staining), due to increased binding of eosin to denatured cytoplasmic proteins and in part to loss of the basophilia
2) More glassy due to loss of glycogen
3) Myelin figures are more prominent
4) Discontinuation of plasma and organelle membranes
5) Dilation of mitochondria
6) Disruption of lysosomes
7) Intra-cytoplasmic myelin figures

ii) Nuclear changes
1) Karyolysis (break down of DNA and chromatin by DNase activity)
2) Pyknosis (nuclear shrinkage and increased basophilia; the DNA condenses into a solid shrunken mass)
3) Karyorrhexis, (the pyknotic nucleus undergoes fragmentation.)
4) Nucleus disappear in 1-2 days

iii) Other
Dead cells may be replaced by myelin figures which is either phagocytosed by other cells or further degraded to fatty acids, fatty acids then bind to calcium salts and ultimately become calcified.