Question

Why would diffusion of O₂ into the blood stop if you stopped breathing or your blood stopped circulating?

Answer 1

Answer: our human body need oxygen to live by producing energy and supply the whole part of the body.

So It depends on the oxygen supply,

• In one aspect the oxygen will comes to the human body through the Inhalation proof respiration ( the air we inhale from the surroundings with consists of oxygen)
• In other aspect our body will get the oxygen for the all parts of the body through the oxygenated blood which is received from the heart through the ascending and descending aorta.

Exchanges of the gases

our lung is the organ which helps in the respiration, specifically the alveoli in the bottom of the lungs will have capillary bed. When we inhale the air through mouth/ nose it goes to the lungs, and in alveoli the oxygen will goes to the deoxygenated blood and make the blood oxygenated.

Then the carbon dioxide removed from the deoxygenated blood will removed from the body through exhalation process of respiration.

Hence, when our body stopped breathing, the the oxygenated air will not goes to the lungs (alveoli) for the exchange of the gases. So there will be lack in oxygen and diffusion of o2 in the blood.

same as ; when our body stopped the blood circulation, then the lungs will not get the blood, so there will be no any exchange of gases and resulted in diffusion of o2 will not occur.