question_answer 58)

    The blood leaving the tissues becomes richer in (a) carbon dioxide           (b) water                             (c) heamoglobin               (d) oxygen

Answer:

                  (a)The blood leaving the tissues becomes richen in CO2. The main artery (aorta) carries oxygenated blood to all the organs of the body from the heart. When the oxygenated blood passes through the capillaries of the body organs/tissues, it gives oxygen to the body cells. At the same time, carbon dioxide produced during respiration enters into blood. Thus, deoxygenated blood (carrying CO2) leaves the tissues and enters the vena cava, from where they are again passed to the lungs for oxygenation.