Bronhiile

Bronhiile are the major air-conducting passages of the lower respiratory tract, connecting the trachea to the lungs. There are two primary bronchi, the right and the left, which branch from the trachea at the carina. The right primary bronchus is shorter, wider, and more vertical than the left, a difference that can influence the site of aspirated material.

Structure and branching form a hierarchical tree: primary bronchi divide into secondary (lobar) bronchi—three on the right and two on the left—which in turn divide into tertiary (segmental) bronchi that supply individual bronchopulmonary segments. In the walls of larger bronchi, cartilage rings or plates provide structural support; as branching continues and the airways become smaller, cartilage becomes patchy and eventually disappears in the smallest bronchi. The bronchial lining consists of pseudostratified ciliated columnar epithelium with goblet cells, which together with the mucociliary apparatus helps clear inhaled particles.

Functionally, bronhiile serve to conduct air to the lungs while conditioning it—warming, humidifying, and filtering it. They also participate in immune defense through resident cells and lymphoid tissue, with mucus production and ciliary movement aiding the clearance of debris and pathogens.

Clinical relevance: inflammation of the bronchi is known as bronchitis; chronic bronchitis is a feature of certain chronic lung diseases and often related to smoking. Bronchi may undergo bronchial hyperreactivity in asthma, or become narrowed in chronic obstructive conditions. Infections or obstructions can affect different levels of the bronchial tree, and diseases of the smaller airways are categorized separately as bronchiolitis or bronchiectasis when structural damage occurs.

Blood supply and innervation: bronchial arteries provide systemic blood flow to the airways; venous drainage is mainly to the azygos system and pulmonary veins. Autonomic nerves from the parasympathetic and sympathetic systems regulate airway tone, with parasympathetic activity tending toward bronchoconstriction.