Theory question 103
Transport in Animals(a) List the main constituent of mammalian blood
(b) State two functions of each constituent
(c) Tabulate six differences between arteries and veins (d) Name the main artery which transports blood to the: (i) Lung (ii) Kidney
Show the model answer
(a) Plasma; red blood cells (erythrocytes); white blood cells (leucocytes); platelets (thrombocytes).
(b) Plasma: carries dissolved food, hormones, urea and carbon dioxide; distributes heat; carries antibodies and clotting proteins.
Red blood cells: carry oxygen as oxyhaemoglobin; help carry carbon dioxide.
White blood cells: engulf (phagocytose) germs; make antibodies/antitoxins.
Platelets: start blood clotting; help seal wounds and stop bleeding/entry of germs.
(c) Arteries | Veins:
carry blood away from the heart | carry blood to the heart;
thick, muscular, elastic walls | thin walls with little muscle;
narrow lumen | wide lumen;
no valves (except at their base) | have valves along their length;
blood under high pressure and flows in spurts | low pressure, smooth flow;
carry oxygenated blood (except pulmonary artery) | carry deoxygenated blood (except pulmonary vein);
usually deep in the body | many near the surface.
(d)(i) Pulmonary artery. (ii) Renal artery.
In (c) each difference must compare the same feature for both vessels.