How do oxygen and carbon dioxide are exchanged in the lunges?

Answer 1

The circulatory and respiratory systems are linked when oxygen/carbon dioxide exchange takes place. It begins in the heart:

Deoxygenated blood enters through the superior and the inferior vena cava. Going through the right atrium and through the tricuspid valve, the blood goes into the right ventricle. The right ventricle then pumps the blood into the pulmonary artery, where it then takes this deoxygenated blood into the lungs.

Meanwhile, when you inhale, oxygen enters the nasal passage and goes down your nasopharynx and oropharynx, and keeps going down through the larynx and trachea. The oxygen finally enters your lungs and enters the small branch-like structures in your lungs called broncioles and goes into even smaller structures called the alveoli, surrounded by small capillaries.

These small capillaries are holding the deoxygenated blood from your heart. So, this exchange between oxygen and carbon dioxide takes place here. The oxygen/carbon dioxide travel through the very thin walls of the capillaries/alveoli and so, the alveoli get the carbon dioxide while the blood in the capillaries gets oxygenated. Now, when you exhale, you breath out all the oxygen. The oxygenated blood then returns to the heart through the pulmonary vein. It enters the left atrium and goes through the mitral valve and then enters the left ventricle which then pumps blood through the aortic valve into the aorta which then delivers oxygenated blood throughout your entire body.