The respiratory system is a complex network of organs and tissues—primarily the lungs, airways (trachea, bronchi), and diaphragm—that enables breathing, gas exchange, and vocalization.

The system is subdivided into upper and lower respiratory tracts. The upper tract include sinuses, nasal cavity pharynx, and larynx, The trachea, bronchi, and bronchioles make up the lower tract. Both are responsible for the processing and delivering air to and from the parenchyma.

Alveoli are tiny, balloon-like air sacs at the end of the bronchioles in the lungs, acting as the primary site for gas exchange between the respiratory and circulatory systems. Surrounded by a dense capillary network, they allow oxygen to enter the blood and carbon dioxide to be exhaled.

The lower respiratory tract includes the trachea which branches into two main bronchi for delivery of air to the lungs. The bronchi branches into two and become narrower as bronchioles. The thinnest and narrowest bronchioles deliver air to the alveolar ducts for gas exchange.

Lungs are the primary pair of spongy, pinkish-gray organs in the chest responsible for gas exchange, bringing in oxygen and expelling carbon dioxide. The lungs house the millions of alveoli responsible for gas exchange.

The diaphragm is a large, dome-shaped sheet of internal skeletal muscle separating the thoracic and abdominal cavities. When contracting and relaxing it alters thoracic pressures facilitating inhalation and exhalation.