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. 2021 Apr 6;299(3):508–523. doi: 10.1148/radiol.2021203711

Figure 2:

Schematic rendering of the functional anatomic unit of gas exchange. The respiratory bronchiole (RespBr) terminating in a group of alveolar sacs (orange) and their associated sac walls (ASW; yellow colored pencil) with pulmonary artery capillaries (red colored pencil) carrying deoxygenated blood to the alveolar walls. Within the alveolar sac plasma carbon dioxide (CO2; orange arrow) undergoes gas exchange and oxygen (O2) diffuses (yellow arrow) into the pulmonary capillary venules to be bound by hemoglobin in the red blood cells. The oxygenated blood then flows into the pulmonary veins (dark blue) back to the left atrium.

Schematic rendering of the functional anatomic unit of gas exchange. The respiratory bronchiole (RespBr) terminating in a group of alveolar sacs (orange) and their associated sac walls (ASW; yellow colored pencil) with pulmonary artery capillaries (red colored pencil) carrying deoxygenated blood to the alveolar walls. Within the alveolar sac plasma carbon dioxide (CO2; orange arrow) undergoes gas exchange and oxygen (O2) diffuses (yellow arrow) into the pulmonary capillary venules to be bound by hemoglobin in the red blood cells. The oxygenated blood then flows into the pulmonary veins (dark blue) back to the left atrium.