Notes on transport

Q1 what is closed circulatory system?
A When the blood flows in closed vessels like arteries veins and capillaries and these vessels don't open anywhere ,this system is called closed circulatory system. The exchange of material takes place through the thin membrane of capillaries.
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Q2 What is the difference between veins and arteries?
A Arteries ----
1 Carry oxygenated blood except pulmonary artery
2 Present deep inside the body
3Thick walled and thin lumen(space)
4 Dont have valves
5 carry blood away from heart
Veins
1 Carry deoxygenated blood except pulmonary vein
2 Present on the surface of the bodty
3 Thin walled and thick lumen
4  Possess valve
5 Bring blood to the heart.
More to continue.....