Venus return is the rate of the blood flow that leads back to the heart. It usually normally limits cardiac output.
The pump is when your muscles will swell up during your workout, which is caused from the excessive amount of blood going into the muscle and filling it up the same way you would kinda fill up a water balloon.
A Respiratory Pump is one of those abdominal and thoracic structures that cause the expansion and contraction of the lungs.
Gravity is the phenomenon by which two bodies having mass are litarally just attracted to each other.
Hope this helps:)
