The respiratory tract is lined with respiratory mucosa or respiratory epithelium.Air is breathed in through the nose or the mouth. In the nasal cavity, a layer of nasal mucosa acts as a filter and traps pollutants and other harmful substances found in the air.The opening of the larynx has a special flap of cartilage, the epiglottis, that opens to allow air to pass through but closes to prevent food from moving into the airway.
From the larynx, air moves into the trachea and down to the intersection known as the carina that branches to form the right and left primary bronchi.
The diaphragm is also the main muscle of respiration involved in breathing, and is controlled by the sympathetic nervous system.
The inner visceral pleura covers the surface of the lungs, and the outer parietal pleura is attached to the inner surface of the thoracic cavity.
