Respiratory System and Oxygen Supply to Organisms


Respiration is the process of exchanging gases between the environments and organisms during which the thoracic volume changes to develop a specific mechanism of pushing the air out of the trachea and pulling the next portion of the air in the trachea. The elements of the mechanism are expiration and inspiration. Respiration is possible because of the elastic respiratory muscles’ work. They control the processes of expiration and inspiration (Martini, 2007, p. 627). The function of respiration is in providing organisms with the necessary oxygen.

Respiratory System

Expiration is the relatively passive process during which muscles of the thoracic cage can relax to push the air out of the trachea, and the diaphragm can return to its relaxing expiratory position. Expiration is necessary to let harmful carbon dioxide be pushed out from the body (Seeley & Stephens, 2008, p. 512). Expiration is connected with inspiration, and it is part of the complex respiration process.

Residual volume is the amount of air remaining in the lungs after the forceful expiration of the most exhalation. This volume is present because the thorax expands, and lungs stretch. The process is closely connected with expiration (Martini, 2007, p. 628). This volume is never eliminated during expiration to preserve the amount of air in the lungs.

External respiration is the process when oxygen and carbon dioxide exchange between the lungs and the blood. Alveolar membranes exchange gases with the blood found in the pulmonary capillaries. External respiration is necessary to provide the blood with oxygen to bring it to cells (Seeley & Stephens, 2008, p. 512). External respiration is necessary to realize the main goal of respiration as the process of gas exchange.


Internal respiration is the process of absorbing oxygen from the blood by cells, in turn, cells release carbon dioxide. As a result, the gas exchange is realized between the blood and all the tissues of the body (Martini, 2007, p. 629). This process is connected with the external respiration and cellular respiration process.


Martini, F. (2007). Anatomy and physiology. USA: Rex Bookstore, Inc.

Seeley, R., & Stephens, T. (2008). Anatomy and physiology. USA: McGraw Hill Higher Education.