Anatomy of tracheobronchial tree
The tracheobronchial tree, also known as the respiratory tree, is the branching system of airways within the respiratory system. It is responsible for conducting air from the external environment into the lungs and facilitating the exchange of oxygen and carbon dioxide. The tracheobronchial tree consists of the following major components:
- Trachea: The trachea, commonly known as the windpipe, is a large tube that extends from the lower part of the larynx (voice box) to the level of the fifth thoracic vertebra in the chest. It is approximately 10-12 cm long in adults. The trachea is lined with ciliated mucous membrane and supported by C-shaped rings of cartilage, which help keep the airway open.
- Main Bronchi: At the lower end of the trachea, it divides into two main bronchi, one for each lung. The right main bronchus is wider, shorter, and more vertical than the left main bronchus.
- Lobar Bronchi: Within each lung, the main bronchi further divide into lobar bronchi, also known as secondary bronchi. The right lung has three lobes, so it has three lobar bronchi, while the left lung has two lobes and thus two lobar bronchi.
- Segmental Bronchi: The lobar bronchi then divide into segmental bronchi, also called tertiary bronchi. These segmental bronchi supply individual segments of the lung, each of which has its own blood supply.
- Bronchioles: The segmental bronchi further divide into smaller bronchioles. These bronchioles have smooth muscle in their walls, allowing them to constrict and dilate to regulate airflow.
- Terminal Bronchioles: The bronchioles continue to divide, becoming even smaller and ending in the terminal bronchioles. Terminal bronchioles are the smallest airways that lack alveoli (air sacs).
- Respiratory Bronchioles: Beyond the terminal bronchioles, the airways contain alveoli, and they are known as respiratory bronchioles. These are the first airways that are involved in gas exchange, as they have some alveoli attached to their walls.
- Alveolar Ducts and Alveoli: The respiratory bronchioles further divide into alveolar ducts, which eventually lead to grape-like clusters of alveoli. Alveoli are the tiny air sacs where oxygen is taken up by the blood, and carbon dioxide is released from the blood during breathing.
The tracheobronchial tree is a highly complex and branching system, allowing for efficient gas exchange in the lungs. The walls of the airways contain cilia and mucus-producing cells that help trap and remove debris and particles from the air, protecting the lungs from potential harm.