Intrapulmonary Bronchi

Intrapulmonary Bronchi divides into lobar/secondary bronchi and segmental/tertiary bronchi. The bronchial wall is divided in five layers:

• Mucosa:
• Epithelium is ciliated columnar. The cell height decreases with decreasing bronchial diameter.
• Basal lamina is present in primary bronchi (conspicuous), and not present in secondary and tertiary bronchi (discrete).
• Lamina propria is similar to that of the trachea. It reduces in proportion to the diameter of the bronchus.
• Muscularis is a continuous layer of smooth muscle in larger bronchi. In smaller bronchi it may appear discontinuous because of spiral arrangement. The contraction regulates the diameter of the airway.
• Submucosa is made of loose connective tissue that contains glands and adipose tissue in larger bronchi.
• Cartilage layer has discontinuous cartilage plates. It becomes smaller as the diameter decreases.
• Adventitia is moderately dense connective tissue. It is continuous with the adjacent structures such as the pulmonary artery and lung parenchyma.