PUMP, PIPES, AND BLOOD PRESSURE

In any enclosed pump-and-pipes system, the pump creates fluid flow and pressure results as the fluid flowing through the pipes encounters resistance, or friction. Every beat of your heart generates a powerful thrust that pumps blood through the pipes of the vascular system, creating pressure in the vessels. Each time the heart relaxes between beats, the pressure in the system falls temporarily, while the pump chambers refill with blood. When the chambers are full, the heart pumps blood through the pipes once again. In hydraulics, this is described as “pulsatile flow,” meaning that the fluid flows in waves, or pulsations, and it’s why blood pressure is described with two numbers. Systolic pressure, the top and larger number in the ratio, is the peak pressure of the fluid in the pipes (arteries) just after the heart has pumped. The diastolic pressure, the bottom and smaller number, refers to the pressure in the pipes between pumps, when the heart is at rest.
Blood pressure is highest in the arteries and arterioles and lowest in the capillaries and veins. Blood oozes from a cut vein, but it spurts from a lacerated artery. This reflects the significant pressure differences between arteries and veins, and it also explains why arteries are the blood vessels most affected by hypertension. Blood pressure is highest of all in the arteries nearest the aorta, the main artery just off the heart. The pressure there is so great that if the aorta itself were lacerated, blood would squirt out five or six feet!
The farther the arteries are from the heart, the lower the pressure becomes, until it reaches the arterioles. The small size of the arterioles creates natural resistance to the blood flowing from the larger arteries. As a result, pressure goes up in the arteries – and up even more when the arterioles constrict. The blood then moves into the capillaries and capillary beds. Blood pressure is necessarily low on these tiny, thin-walled, fragile vessels. Blood leaving the capillaries and entering the venules and veins remains under low pressure – too low, in fact, for the blood to return to the heart without some help. Therefore, blood flow in the venous system is assisted by the respiratory and muscular pumps and the venous valves.
*11/313/5*

PUMP, PIPES, AND BLOOD PRESSUREIn any enclosed pump-and-pipes system, the pump creates fluid flow and pressure results as the fluid flowing through the pipes encounters resistance, or friction. Every beat of your heart generates a powerful thrust that pumps blood through the pipes of the vascular system, creating pressure in the vessels. Each time the heart relaxes between beats, the pressure in the system falls temporarily, while the pump chambers refill with blood. When the chambers are full, the heart pumps blood through the pipes once again. In hydraulics, this is described as “pulsatile flow,” meaning that the fluid flows in waves, or pulsations, and it’s why blood pressure is described with two numbers. Systolic pressure, the top and larger number in the ratio, is the peak pressure of the fluid in the pipes (arteries) just after the heart has pumped. The diastolic pressure, the bottom and smaller number, refers to the pressure in the pipes between pumps, when the heart is at rest.Blood pressure is highest in the arteries and arterioles and lowest in the capillaries and veins. Blood oozes from a cut vein, but it spurts from a lacerated artery. This reflects the significant pressure differences between arteries and veins, and it also explains why arteries are the blood vessels most affected by hypertension. Blood pressure is highest of all in the arteries nearest the aorta, the main artery just off the heart. The pressure there is so great that if the aorta itself were lacerated, blood would squirt out five or six feet!The farther the arteries are from the heart, the lower the pressure becomes, until it reaches the arterioles. The small size of the arterioles creates natural resistance to the blood flowing from the larger arteries. As a result, pressure goes up in the arteries – and up even more when the arterioles constrict. The blood then moves into the capillaries and capillary beds. Blood pressure is necessarily low on these tiny, thin-walled, fragile vessels. Blood leaving the capillaries and entering the venules and veins remains under low pressure – too low, in fact, for the blood to return to the heart without some help. Therefore, blood flow in the venous system is assisted by the respiratory and muscular pumps and the venous valves.*11/313/5*

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