The continuity of the vascular system continues where the capillaries are fed with oxygen-free blood and opened to venules or small veins, The pressure in the systemic circulation is different. In the aorta and large arteries, blood pressure ranges from 120-80 mmHg throughout the cardiac cycle. Then the pressure decreases in proportion to the resistance encountered in the vascular circuit, The average pressure at the end of the arterioles of the capillaries is 30 mmHg. As the blood enters the veins, the resistance to the blood flow completely disappears. In time, the blood reaches the right atrium. Pressure has dropped down to zero