The number of consumers increases
1. energy
2.thermal equilibrium
3.heat
4.thermal energy
5.thermal expansion
6.temperature
It is separated by the endocardium !
A relatively small blood pressure gradient is generally insufficient to move blood through the veins under given conditions, thus venous return must be facilitated by valves within veins and two "pumps." ... As skeletal muscles contract, veins are squeezed to help propel the blood toward the heart.
