1. What is the difference between ischemia and infarction? Explain the pathophysiological

mechanisms involved in each condition.

- Ischemia is the reduced blood supply to a tissue or organ, resulting in impaired oxygen

delivery and cellular metabolism. Infarction is the death of tissue or organ due to prolonged

ischemia and irreversible damage. The pathophysiological mechanisms involved in ischemia

include vasoconstriction, thrombosis, embolism, vasospasm, and compression. The

pathophysiological mechanisms involved in infarction include inflammation, necrosis,

apoptosis, and repair.

2. What are the three stages of acute inflammation? Describe the main cellular and vascular

events that occur in each stage.

- The three stages of acute inflammation are vascular, cellular, and resolution. In the vascular

stage, there is increased blood flow, vasodilation, increased vascular permeability, and

edema. In the cellular stage, there is migration of leukocytes, chemotaxis, adherence,

transmigration, phagocytosis, and release of inflammatory mediators. In the resolution stage,

there is termination of the inflammatory response, removal of debris, and healing or repair.

3. What are the four types of hypersensitivity reactions? Give an example of each type and

explain the immunological mechanism involved.

- The four types of hypersensitivity reactions are type I (immediate), type II (cytotoxic), type III

(immune complex), and type IV (delayed). An example of type I hypersensitivity is

anaphylaxis, which is caused by IgE-mediated mast cell degranulation and release of

histamine and other mediators. An example of type II hypersensitivity is hemolytic anemia,

which is caused by IgG- or IgM-mediated complement activation and lysis of red blood cells.

An example of type III hypersensitivity is serum sickness, which is caused by IgG- or IgMmediated formation of immune complexes that deposit in tissues and activate complement.

An example of type IV hypersensitivity is contact dermatitis, which is caused by T cellmediated activation of macrophages and release of cytokines.