Ventilation is the movement of air into and out of the [[Lungs - Anatomy & Physiology|lungs]]. Air moves from high pressure to low pressure with the rate of flow being proportional to the pressure difference. As environmental pressure is generally constant, the [[Cardiorespiratory System Overview - Anatomy & Physiology|respiratory system]] must change it's internal pressure to maintain air flow. | Ventilation is the movement of air into and out of the [[Lungs - Anatomy & Physiology|lungs]]. Air moves from high pressure to low pressure with the rate of flow being proportional to the pressure difference. As environmental pressure is generally constant, the [[Cardiorespiratory System Overview - Anatomy & Physiology|respiratory system]] must change it's internal pressure to maintain air flow. |