Tuberculosis pathology is hard?

[scilearner]

Hello,

 

I'm reading tuberculosis pathology and I'm finding it hard to understand because my general poor knowledge in pathology. This is what I gathered from the reading.

 

1. Tubercle bacilli reach alveoli of lung and ingested by macrophages.

2. Then macrophages call other macrophages and T cells to wall off the bacilli in lung(forming a tubercle). Now my question is phagosome-lysosome fusion is inhibited by these bacilli, how can macrophages kill these bacilli. Now what is the difference between this tubercle and a granuloma. In a granuloma is it only macrophages that wall off the foreign substance or T cells as well.

3. After few weeks macrophages die releasing bacilli and forming caseous necrotic centre. Why does this cause caseous necrosis, is any necrosis in lung causes cheesy like appearance which is called caseous, is caseous necrosis always covered by granuloma.

4. Now when the tubercle/granuloma ruptures how do cavities form in lungs, and how does this allow for the infection to spread in lung?

6.Why is this a type IV hypesensitivity reaction?

5. What on earth is Ghon's complex?

 

Thanks