Lung Structure and Ventilation



The respiratory system is responsible for multiple functions, the most important being the delivery of oxygen to the body and removal of carbon dioxide from the body. The upper and lower respiratory tracts function together to bring about respiration. Air moves from the nose, down the trachea, into the lungs, and ends at the alveoli, which is the terminal site of gas exchange. Muscles of the rib cage, muscles of the abdominal wall, and the diaphragm muscle work together to draw air into the lungs and expel air from the lungs. The functional ability of a person's lungs can be tested using spirometry. Spirometry involves breathing into a machine to measure the amount of air at any given stage of the breathing process.

At A Glance

  • The primary function of the respiratory system is to exchange gases with the environment. The respiratory system also plays roles in communication, olfaction, pH balance, and regulation of blood pressure. The lungs aid in the mobilization of abdominal contents and act as a respiratory pump to promote venous return and lymph flow.
  • The upper respiratory tract includes the nose, pharynx, larynx, and trachea. The lower respiratory tract includes the bronchi, bronchioles, lungs, alveoli, and pleural cavities.
  • The relaxation and contraction of the diaphragm and external intercostal muscles expand and contract the thoracic cavity. The expansion and contraction of the thoracic cavity creates pressure changes in the pleural space, which allows air to move into and out of the lungs.
  • Spirometry measures or estimates tidal volume, inspiratory reserve volume, expiratory reserve volume, residual volume, vital capacity, and total lung capacity.