$(a)$ How does the exchange of respiratory gases,oxygen and carbon dioxide,take place between tissues and blood in human beings?
$(b)$ Name the respiratory pigment in humans. Where is it found?

(N/A) In tissues,oxygen is consumed for metabolic activities,leading to a low concentration of oxygen and a high concentration of carbon dioxide. Conversely,blood arriving from the lungs has a high concentration of oxygen and a low concentration of carbon dioxide. Due to this partial pressure gradient,gases move between the blood and tissues via the process of simple diffusion.
$(b)$ The respiratory pigment in humans is Haemoglobin. It is found inside the Red Blood Corpuscles $(RBCs)$.