Question

when is blood bright red-coming from the lungs or going back to the lungs??

Answer 1

Blood is bright red when it comes from the lungs.

Blood leaving heart and moving to lungs through pulmonary vein, get oxygenated in lungs.

Hence, the haemoglobin present in blood which is a oxygen carrier get full and hence start giving freshness.

This total oxygenation of haemoglobin is responsible for bright red color blood.

Answer 2

Hemoglobin is contained in red blood cells, which efficiently carries oxygen from the lungs to the tissues of the body. Hemoglobin also helps in the transportation of carbon dioxide and hydrogen ions back to the lungs.