Why doesn't primary tb occur in lung apices like secondary tb does?

TB: It can. The primary focus is usually the right lower lobe because that is the easiest site of entry for inhaled droplet nuclei containing afb. When the infection reaches the local nodes they suppurate, erode into an adjacent artery and the m. Tbc then spreads throughout the body to the areas with most blood flow. Either the patient then forms multiple granulomas or goes on to develop miliary tb.