Trachea is also known as the windpipe. It is a tube about 10-12.5 cm long (4-5 inches) and about 2.5 cm wide (1 inch).
The trachea extends from the lower edge of the larynx downward into the thoracic cavity, where it splits into right and left bronchi. Rings of cartilage keep the airway open.
Functions of the trachea:
- to conduct air to and from the lungs;
- to filter air;
- to trap particles in mucus.
The Bronchial tree consists of bronchi, bronchioles, and alveoli.
Bronchi are formed as the lower part of the trachea divides into two tubes. The primary portion enters the lungs at a region called the hilus. The primary branch forms a secondary branch, which then branches into smaller tertiary bronchi.
- The left bronchus is narrow and positioned more horizontally than the right bronchus.
- The right bronchus is shorter and wider than the left and extends downward in a more vertical direction. Because of the difference in size between the two, objects are more easily inhaled (aspirated) into this portion of the bronchi.
Bronchioles are smaller tube divisions of the bronchi. Its walls contain smooth muscle and no cartilage. This allows contraction and relaxation, thereby regulating air flow to the alveoli.
Alveoli are tiny ends of the alveolar ducts. These tiny air sacs function to exchange oxygen and carbon dioxide in the blood. Certain respiratory diseases cause a thickening of the alveoli walls, which restricts movement, causing breathing difficulties.