stages of tuberculosis

(Stage 1) What happens first in TB infection?

Bacteria are inhaled into the lungs and taken up by alveolar macrophages

(Stage 1) Can macrophages kill TB immediately?

No — TB survives and multiplies inside macrophages

(Stage 2) What structure forms to contain TB?

Granuloma (tubercle)

(Stage 2) What is inside a granuloma?

Infected macrophages surrounded by immune cells

(Stage 2) Purpose of granuloma?

Walls off bacteria to prevent spread

(Stage 3)What is latent TB?

Bacteria are alive but inactive, no symptoms

(Stage 3) Can latent TB be contagious?

No

(Stage 3) What keeps TB controlled?

Immune system (low O₂, low pH in granuloma)

(Stage 4)When does TB become active?

When immune system weakens (stress, HIV, age)

(Stage. 4) What happens in active TB?

Granuloma breaks down → bacteria spread

(Stage 5) What is caseous necrosis?

Tissue death that looks “cheese-like”

(Stage 5) What happens when granuloma ruptures?

• Forms lung cavities

• Releases bacteria → spreads infection

What are the stages of TB in order?

1. Inhalation → macrophages infected

2. Granuloma (tubercle) forms

3. Latent TB (asymptomatic)

4. Reactivation → active TB

5. Tissue destruction & spread