Bronchial tree

Bronchial tree refers to the system of airways in the respiratory system that conducts air into the lungs. The bronchial tree can be likened to an actual tree, with the trachea representing the trunk and the multiple smaller branches representing the bronchi and bronchioles.

Structure

The bronchial tree starts from the trachea, which divides into two primary bronchi at the carina. Each primary bronchus enters a lung, where they further divide into secondary bronchi, also known as lobar bronchi. Each lobar bronchus supplies a lobe of the lung; three on the right and two on the left. The lobar bronchi further divide into tertiary bronchi, also known as segmental bronchi, each supplying a bronchopulmonary segment.

The segmental bronchi continue to divide into smaller and smaller bronchi, eventually becoming bronchioles. The bronchioles further divide into terminal bronchioles, which are the smallest airways without alveoli. The terminal bronchioles then divide into respiratory bronchioles, which are interspersed with alveoli and lead to alveolar ducts and alveolar sacs, where gas exchange occurs.

Function

The primary function of the bronchial tree is to conduct air from the trachea into the lungs. It also warms and humidifies the air, and filters out foreign particles and microorganisms. The bronchial tree is lined with ciliated epithelium, which helps to move mucus and trapped particles out of the lungs.

Clinical significance

Diseases of the bronchial tree include asthma, bronchitis, bronchiectasis, and lung cancer. In asthma, the bronchial tree becomes hyperresponsive and constricts in response to triggers such as allergens, cold air, or exercise. In bronchitis, the bronchial tree becomes inflamed and produces excess mucus, leading to cough and difficulty breathing. In bronchiectasis, the bronchial tree becomes abnormally widened, leading to recurrent infections and impaired clearance of mucus. In lung cancer, malignant cells can originate from the bronchial tree and spread to other parts of the body.

See also

• Respiratory system
• Lung
• Asthma
• Bronchitis
• Bronchiectasis
• Lung cancer