What occurs during external respiration?

During external respiration, gas exchange occurs between the lungs and the external environment. This process involves the inhalation of oxygen-rich air from the environment into the lungs, where oxygen diffuses into the blood, and carbon dioxide from the blood is expelled out of the lungs into the external environment during exhalation. This exchange is essential for maintaining adequate levels of oxygen in the blood, which is crucial for the body's metabolic processes.

The focus of external respiration is primarily on the interface between the alveoli in the lungs and the capillaries surrounding them. The effectiveness of this gas exchange process relies on several factors, including the partial pressure differences of gases, the surface area of the alveoli, and the permeability of the alveolar-capillary membrane.

Understanding this process is crucial for grasping the broader context of respiration, which also includes internal respiration, where gas exchange occurs at the cellular level between blood and tissues, and various physiological mechanisms involved in maintaining respiratory function.