Which does NOT contribute to venous blood pressure?

• A. Skeletal muscle activity
• B. Respiratory movements
• C. Valves in veins
• D. Cardiac contractions

Answer: (A)

The concept to focus on is how venous return and venous pressure are generated. Venous pressure is shaped by pressure gradients pulling blood back toward the heart, and by mechanisms that keep that flow unidirectional. Respiratory movements create intrathoracic pressure changes that suck blood toward the heart, helping venous return. Vein valves prevent backward flow, maintaining forward movement and supporting a steady gradient into the heart. Cardiac contractions influence pressure gradients as blood is propelled through the heart, but they are primarily about arterial pumping rather than setting the venous pressure.

Skeletal muscle activity around veins does not establish the steady venous pressure; instead, it serves as a transient pump that increases venous return by pushing blood toward the heart when muscles contract. So while it helps move blood, it does not contribute to the baseline venous blood pressure in the same way the respiratory pump, valves, and cardiac-driven pressure gradients do.