This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pathology
Type of necrosis occuring in brain? 
Select and explain. 
A. Coagulative, B. Liquefactive, C. Fibrinoid, D. Caseous
B: Liquefactive
Answer: B: Liquefactive 
Explanation: Ans. is 'b' i.e., Liquefactive Coagulative necrosis This is most common type of necrosis. This type of necrosis is most frequently caused by sudden cessation of blood flow (ischemia) in organs such as hea (MI), Kidney (ATN), adrenal gland, and spleen. Note : Brain is the only exception, i.e.,. It is the only solid organ in which ischemia leads to liquifactive necrosis not coagulative necrosis. It is also seen with other types of injury e.g., liver necrosis in viral hepatitis, Coagulative necrosis of skin after burns (Thermal injury). Why there is predominant protein denaturation and no enzymatic digestion ? Hypoxia causes intracellular acidosis (has been explained earlier) .1, pH results in denaturation of proteins which includes not only structural proteins but also enzymes --) So, there is no enzymatic digestion. The necrotic cells retain their cellular outline for several days. Liquefactive necrosis It is the necrotic degradation of tissue that rapidly undergo softening and liquefaction because of the action of hydrolytic enzymes. It occurs after Infection i.e., suppurative inflammation (most common). Ischemic necrosis in brain. Note : Brain lacks any substantial suppoive stroma, so ischemic necrosis in brain is liquifactive unlike other organs where it is coagulative. Mechanism of liquefactive necrosis --> Microbes stimulates accumulation of inflammatory cells and these cells release lysosomal enzymes. Caseous necrosis It is a variant of coagulative necrosis. It is most commonly encountered when cell death is attributable to ceain organisms e.g., mycobacterium tuberculosis (TB) and fungi (Histoplasma, Coccidioidomycosis). Why is it called caseous necrosis, not coagulative necrosis ? In contrast to coagulative necrosis where tissue architecture is maintained, in caseous necrosis, the tissue architecture is completely obliterated. So, it has been called caseous because of its cheesy white appearance of the area of necrosis.