EVERYDAY SCIENCE

Detailed explanation-1: -Red blood cells contain a protein called hemoglobin, which carries oxygen from the lungs to all parts of the body .

Detailed explanation-2: -Red blood cells squeeze through narrow capillaries in single file. Haemoglobin molecules inside red blood cells pick up and carry the oxygen. These oxygen-rich cells travel in the blood vessels from the lungs to the left side of the heart. The blood is then pumped around the body.

Detailed explanation-3: -After leaving the heart, the red blood cell travels through the pulmonary artery to the lungs. There it picks up oxygen making the deoxygenated red blood cell now an oxygenated blood cell. The blood cell then makes it way back to the heart via the pulmonary vein into the left atrium.

Detailed explanation-4: -Red blood cells are contained within blood, which circulates throughout the body in arteries and veins. In this sense, red blood cells are part of the circulatory system.