Final answer:
Blood is assisted back to the heart in veins through valves preventing backflow and the skeletal muscle pump. Pressure changes from breathing (respiratory pump) and vascular tone also contribute.
Step-by-step explanation:
How Blood is Helped Back to the Heart in Veins
One way that blood is helped back to the heart in veins is through the presence of valves that prevent backflow of blood. This ensures that blood only moves in one direction, towards the heart. A second important mechanism is the skeletal muscle pump, where the contraction of muscles during body movements compresses the veins, acting like a pump to push blood towards the heart.
Another significant assistive factor is the respiratory pump, which utilizes the pressure changes in the thoracic and abdominal cavities during breathing to help pull and push blood back to the heart. Venous pressure is also facilitated by the maintenance of vascular tone, where constriction of venous walls helps to move blood more effectively.