Veins and venules can intrinsically act as blood reservoirs in the human body, holding approximately 64% of the total blood volume at any given moment. They have a larger lumen and more distensible walls than arteries. This allows them to expand readily, accommodating a large blood volume at low pressure. Due to their high capacitance, the veins are also referred to as capacitance vessels. When the body requires quick blood redistribution, such as during intense skeletal muscle activity, the cardiovascular center in the medulla oblongata triggers venoconstriction. Through this process, the veins constrict and increase the blood pressure, facilitating faster blood distribution to the heart and skeletal muscles. Additionally, about 21% of venous blood is found in the venous networks within the liver, bone marrow, and integument, referred to as the venous reserve. Through venoconstriction, this reserve volume of blood can quickly return to the heart, ready for redistribution elsewhere in circulation.