Veins transport blood towards the heart. Blood Pressure in the veins → much lower than the blood pressure in the arteries. Blood flows → more slowly and smoothly in the viens. Hence → walls of the veins need not be as thick and muscular as those of arteries of about the same size.
Veins also contain less elastic tissue. → instead most veins have internal valves along their length → to prevent backflow of blood.
Veins → carry deoxygenated blood (except for pulmonary veins which carry oxygenated blood from the lungs to the Heart) → formed when venules join together.
