Changes

*Gas exchange between the air within the alveoli and the pulmonary capillaries occurs by ''diffusion''. The oxygen must first dissolve before passing through the [[Respiratory Epithelium - Anatomy & Physiology|respiratory epithelium]].

*Gas exchange between the air within the alveoli and the pulmonary capillaries occurs by ''diffusion''. The oxygen must first dissolve before passing through the [[Respiratory Epithelium - Anatomy & Physiology|respiratory epithelium]].

*Gas moves from a region of high partial pressure to a region of low partial pressure, down a '''partial pressure gradient'''. P

*Gas moves from a region of high partial pressure to a region of low partial pressure, down a '''partial pressure gradient'''. Partial pressure is the

*The distance between the air within the alveoli, and the blood is approx 0.7micrometers. This distance is decreased during [[Ventilation - Anatomy & Physiology#Inhalation|inhalation]], as the [[Lungs - Anatomy & Physiology|lung]] distends. This tiny distance allows extremely fast and efficient diffusion.

*The distance between the air within the alveoli, and the blood is approx 0.7micrometers. This distance is decreased during [[Ventilation - Anatomy & Physiology#Inhalation|inhalation]], as the [[Lungs - Anatomy & Physiology|lung]] distends. This tiny distance allows extremely fast and efficient diffusion.