THORAX ABDOMEN AND PELVIS

Detailed explanation-1: -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-2: -In a process called diffusion, oxygen moves from the alveoli to the blood through the capillaries (tiny blood vessels) lining the alveolar walls. Once in the bloodstream, oxygen gets picked up by the hemoglobin in red blood cells.

Detailed explanation-3: -This process of exchange of O2 from the atmosphere with CO2 produced by the cells is called breathing, commonly known as respiration.

Detailed explanation-4: -Answer and Explanation: Alveoli of the lungs make close contact with blood capillaries. When a person inhales oxygen, alveoli are filled with more oxygen; thus, oxygen moves to from alveoli to blood capillaries with the help of diffusion (movement of particles from higher to lower concentration).