Description
The lower respiratory system (or lower respiratory tract) consists of all the respiratory structures below the vocal folds of the larynx, including the trachea, lungs, and bronchopulmonary tree (bronchi, bronchioles, and alveoli).
The bronchopulmonary tree is the extensively branched region of the respiratory system. It appears like an inverted tree, with the trachea representing its trunk, the bronchi and bronchioles representing its branches, and the alveoli representing its leaves.
The alveoli lie adjacent to the capillaries of the pulmonary circulation, and it is at these sites where the process of respiration occurs. This process involves the gaseous exchange of oxygen and carbon dioxide across the blood-gas barrier, between the alveoli and pulmonary capillaries. At this site, oxygen diffuses from the inspired air into the blood, while carbon dioxide diffuses from the blood into the expired air.
Related parts of the anatomy
