Which of the following are the basic mechanisms that explain venous return?
I.Muscular "milking" of leg veins containing one-way valves
II.Sympathetic venous constriction
III.Cardiac pumping action, creating a "cardiac suction"
IV.Subatmospheric intrathoracic pressures during breathing

Question

Quizplus · Accepted Answer

The veins manage to return blood to the heart against the force of gravity through four basic mechanisms: 
(1) muscular "milking" of leg veins containing one-way valves; 
(2) sympathetic venous constriction; 
(3) cardiac pumping action, creating a "cardiac suction"; and 
(4) subatmospheric intrathoracic pressures during breathing. The normal subatmospheric pressure within the chest cavity aids venous return because abdominal venous pressure is positive.

Which of the Following Are the Basic Mechanisms That Explain