The two distinct types of respiration utilized by humans are called internal respiration and external respiration. Internal respiration is also called systematic gas exchange, and it is an exchange of oxygen and carbon dioxide in the blood vessels and tissue cells of the lungs and throughout the rest of the body. Because the pressure of the blood vessels in the systemic capillaries is higher than in the pressure in the tissue cells in the lungs and throughout the body, oxygen is forced out of those capillaries and into the tissues of the lungs and the ret of the body. Carbon dioxide, on the other hand, moves from the tissues of the lungs and other body tissues back into the systemic capillaries. Tissues create carbon dioxide on a constant basis, and when it is forced into the systemic capillaries, it is then returned to the heart for re-oxygenation. The rate at which this exchange of oxygen and carbon dioxide occurs is dependent on many things. The pressure differences between the oxygen and the carbon dioxide is one factor. Altitude is another. Also, the airflow rate into and out of the lungs can impact the rate.
External respiration occurs only in the lungs and does not occur throughout the entire body like internal respiration does. External respiration is also called pulmonary gas exchange, and it is the movement of oxygen from the alveoli in the lungs into the pulmonary capillaries as well as the movement of carbon dioxide from the pulmonary capillaries into the lungs. External respiration is the process of re-oxygenating de-oxygenated blood. “Although this process is commonly called an ‘exchange’ of gases, each gas diffuses independently from the area where its partial pressure is higher to the area where its partial pressure is lower” (Tortoria & Derrickson, 2013, p. 864). Internal and external respiration occur in conjunction with and in close relationship to one another to complete the respiratory cycle.
- Tortoria, G.T. & Derrickson, B. (2013). Principles of anatomy & physiology. Hoboken, NJ: Wiley.
