True about Ghon's focus -
Inhaled tubercule bacilli implanted in the distal air spaces of the lower part of upper lobe or upper part of the lower lobe, close to the pleura. This area is about 1 to 1.5 cm with caseating necrosis known as Ghon's focus.
Primary complex or Ghon's complex of tuberculosis consists of 3 components.


Pulmonary compound or Ghon's focus.
Draining lymphatics
Caseating hilar lymph node
Left apical parenchymal lesion
Right apical parenchymal lesion
Sub pleural caseous lesion in right upper lobe
Subpleural caseous lesion just above or below interlobar fissure