Final answer:
Blood pressure is the pressure exerted by blood on the walls of blood vessels. Blood flow is regulated by blood vessel size, smooth muscle action, one-way valves, and fluid pressure. Blood flows the fastest in the aorta and arteries, and the slowest in the capillaries, where important exchanges occur.
Step-by-step explanation:
Blood pressure (BP) is the pressure exerted by blood on the walls of a blood vessel that helps to push blood through the body.
Systolic blood pressure measures the amount of pressure that blood exerts on vessels while the heart is beating.
The optimal systolic blood pressure is 120 mmHg. Diastolic blood pressure measures the pressure in the vessels between heartbeats. The optimal diastolic blood pressure is 80 mmHg.
Blood flow through the body is regulated by the size of blood vessels, by the action of smooth muscle, by one-way valves, and by the fluid pressure of the blood itself.
Blood is pushed through the body by the action of the pumping heart. With each rhythmic pump, blood is pushed under high pressure and velocity away from the heart, initially along the main artery, the aorta. In the aorta, the blood travels at 30 cm/sec.
As blood moves into the arteries, arterioles, and ultimately to the capillary beds, the rate of movement slows dramatically to about 0.026 cm/sec, one-thousand times slower than the rate of movement in the aorta.
While the diameter of each individual arteriole and capillary is far narrower than the diameter of the aorta, and according to the law of continuity, fluid should travel faster through a narrower diameter tube, the rate is actually slower due to the overall diameter of all the combined capillaries being far greater than the diameter of the individual aorta.
Blood flows the fastest in the aorta and arteries, where the blood is under high pressure and velocity. Conversely, blood flows the slowest in the capillaries, where the rate of movement is dramatically reduced.
This slowing of blood flow in the capillaries is important functionally because it allows for the exchange of gases, nutrients, and waste products between the blood and the surrounding tissues.