Bronkialtreet

Bronkialtreet, or the bronchial tree, is the branching system of airways within the lungs that transports air from the trachea to the gas-exchange regions. It begins at the carina, where the trachea divides into the right and left main bronchi, and continues through progressively smaller bronchi and bronchioles, down to the terminal bronchioles and beyond.

Structural features vary along the tree. The trachea and the main bronchi contain C-shaped cartilage rings and submucosal glands. As airways branch into smaller bronchi, cartilage becomes discontinuous and eventually disappears in the bronchioles. The epithelium changes from pseudostratified ciliated columnar with goblet cells to simple cuboidal cells in the smaller conducting airways. Smooth muscle encircles the bronchioles, enabling regulation of airway diameter.

Functions and physiology: The bronchial tree conducts, conditions, and filters air; warms and humidifies inhaled air; and clears mucus via ciliary movement and goblet-cell secretion. It also serves as an immunological barrier and contributes to airway resistance through smooth muscle tone. The conducting region ends at the terminal bronchioles, while respiratory bronchioles and alveolar ducts form the transition to the gas-exchange regions.

Clinical relevance: Disorders such as asthma, chronic obstructive pulmonary disease (COPD), bronchitis, and bronchiectasis involve the bronchial tree. Diagnostic procedures, including bronchoscopy, visualize the airways and may obtain samples or deliver therapy. Treatments frequently target inflammation, mucus production, and bronchial smooth muscle to improve airflow.

Development and variation: The bronchial tree develops from foregut endoderm with branching morphogenesis guided by signaling pathways such as FGF and SHH. In adults, anatomy varies among individuals and species, with differences in length, number of branches, and airway calibers.