Flexi Says: In air-breathing vertebrates, such as humans, respiration of oxygen includes four stages: Ventilation from the atmosphere into the alveoli of the lungs. Pulmonary gas exchange from the alveoli into the pulmonary capillaries. Gas transport from the pulmonary capillaries through the circulation to the peripheral capillaries in the organs. Peripheral gas exchange from the tissue capillaries into the cells and mitochondria.
