THORAX ABDOMEN AND PELVIS

Detailed explanation-1: -CAPILLARIES are blood vessels in the walls of the alveoli. Blood passes through the capillaries, entering through your PULMONARY ARTERY and leaving via your PULMONARY VEIN. While in the capillaries, blood gives off carbon dioxide through the capillary wall into the alveoli and takes up oxygen from air in the alveoli.

Detailed explanation-2: -Air has a higher concentration of oxygen than blood entering the alveolus. Thus, oxygen moves into blood. The opposite is true for carbon dioxide where air has a lower concentration of carbon dioxide. Thus, carbon dioxide moves out of blood and into the air present in alveolus.

Detailed explanation-3: -Gas exchange occurs in the lungs between alveolar air and the blood of the pulmonary capillaries. For effective gas exchange to occur, alveoli must be ventilated and perfused. Ventilation (V) refers to the flow of air into and out of the alveoli, while perfusion (Q) refers to the flow of blood to alveolar capillaries.