Answer
The main contributors of venous return are following :
1. Valves in large veins
2. Skeletal muscle pump
3. Respiratory pump
Work Step by Step
Valves in large veins prevents blood from flowing backward, away from heart. Skeletal muscle pump is a process by which the muscles around the veins contract and pushes the blood towards the heart. During breathing pressure increases in abdominal cavity and decreases in thorax which pulls the blood up towards the heart, this process is the respiratory pump.
