The epithelium of conducting zone

Pseudostratified columnar epithelium up to secondary bronchus;

then, changed to simple columnar epithelium in large bronchiole --> simple cuboidal in small bronchiole, terminal bronchiole

Portion of parietal pleura that covers the diaphragm extends to the following levels:

The lower border of the lung is usually located two intercostal spaces above the respective pleural border.

Thoracentesis, therefore, should be performed between

• 5th and 7th ribs along the midclavicular line,
• 7the and 9th ribs along the midaxillary line, and
• 9th and 11th ribs along the paravertebral line.

The Reid index is the ratio of the thickness of the mucous gland layer in the bronchial wall submucosa to the thickness of the bronchial wall between the respiratory epithelium and bronchial cartilage. It is a sensitive measure of mucous gland enlargement.

E.g elevations of the Reid index above the normal value of 40% correlate well with the duration and severity of chronic bronchitis.