Veins are the blood vessels that carry blood back to the heart from the extremities, once the oxygen has been delivered to the tissues.
The vein wall has the same layers as the arterial wall, but it is much thinner. This is due to the the Media layer (the muscle layer) being much thinner.
Blood flows back to the chest from the legs through the veins.
As the blood is not being pushed back by the heart, it has Low Pressure and Smooth Flow when you are lying down at rest.
This is why veins do not Pulsate - you can't feel a pulse in the veins
Therefore the important things to realise at this stage are:
1] Veins contain blood flowing smoothly and at low pressure
2] Veins have thin walls but still have endothelium next to the blood stopping the blood from clotting in the vein.
