Which of the following helps return blood to the heart?

• A. Lymphatic drainage
• B. Arterial pressure
• C. Pulmonary ventilation
• D. Skeletal muscle contractions

Answer: (D)

Verified step by step guidance

1. Understand the problem: The question asks which mechanism helps return blood to the heart. This involves understanding the circulatory system and the role of various physiological processes in venous blood flow.
2. Recall the anatomy and physiology of veins: Veins have one-way valves that prevent backflow and rely on external forces to help move blood toward the heart, as they do not have the same pressure as arteries.
3. Identify the role of skeletal muscle contractions: Skeletal muscles contract and compress nearby veins, pushing blood through the one-way valves toward the heart. This is known as the 'muscle pump' mechanism.
4. Eliminate incorrect options: Lymphatic drainage is involved in returning interstitial fluid to the circulatory system, not directly in venous blood flow. Arterial pressure drives blood away from the heart, not toward it. Pulmonary ventilation primarily aids in gas exchange, not venous return.
5. Conclude that skeletal muscle contractions are the correct answer because they play a direct role in assisting venous blood return to the heart by utilizing the muscle pump mechanism.