Transport In Human

Because they have large surface area to volume ratio as they are small

Transport oxygen

-biconcave disc to increase surface area to get more oxygen by diffusion -no nucleus to provide more space to be packed with haemoglobin to carry more oxygen Contain haemoglobin to carry oxygen

Transport water, dissolved nutrients,wastes, hormones,heat energy, carbon dioxide

Plasma Cells

Phagocytes Lymphocytes

Kill pathogen Engulfs pathogn and digested by hydrolytic enzyme

-Produce antibodies -Identify foregin antigens and produce antibodies that stick to this antigen -antibody label pathogen to be engulfed by phagocytes -lymphocytes form memory cells to recognize pathogen upon second exposure

When blood vessel are cut and tissues are damaged platelets release enzyme that change prothrombin to thrombin which activates change of fibrinogen(soluble) to fibrin that form network of fibres that traps blood cells form blood clot which develops into scab that stop bleeding and prevent entry of pathogens

Stop blood loss Prevent entry of microorganisms

Arteries have strong wall to withstand the high pressure Narrow lumen to maintain high pressure Contains muscles and elastic tissues to vasoconstriction and vasodilatation

Transport oxygenated blood to body

Thin wall for short diffusion distance for faster rate of diffusion Large surface area for faster diffusion Pores between their cells for facillate diffusion Contain valves to prevent back flow of blood

Carry blood back to heart Lumen wide to decrease resistance to blood flow Contain valves to stop blood flowing backwards Thin wall to be easily swueezed by skeletal muscles