ANATOMY

Detailed explanation-1: -The lungs and respiratory system allow us to breathe. They bring oxygen into our bodies (called inspiration, or inhalation) and send carbon dioxide out (called expiration, or exhalation). This exchange of oxygen and carbon dioxide is called respiration.

Detailed explanation-2: -Lungs contain specialised structures called alveoli which are the site of exchange of oxygen and carbon dioxide between the blood and air. Hence, the alveoli are responsible for absorption of oxygen into the blood.

Detailed explanation-3: -During gas exchange oxygen moves from the lungs to the bloodstream. At the same time carbon dioxide passes from the blood to the lungs. This happens in the lungs between the alveoli and a network of tiny blood vessels called capillaries, which are located in the walls of the alveoli.

Detailed explanation-4: -Cellular respiration converts ingested nutrients in the form of glucose (C6H12O6) and oxygen to energy in the form of adenosine triphosphate (ATP). CO2 is produced as a byproduct of this reaction. The O2 needed for cellular respiration is obtained via inhalation.