Give scientific reasons for the following statements:
Blood flows in arteries in spurts and is under pressure.
Topic: Blood flow in arteries
Answer
Because the blood is driven into the arteries by the CONTRACTION OF THE VENTRICLES, which occurs rhythmically rather than continuously. Each contraction forces a surge of blood into a vessel of NARROW LUMEN, so the flow comes in SPURTS and at HIGH PRESSURE.
The reason must connect the RHYTHMIC ventricular contraction to the spurting flow — blood surges because the pump beats rather than runs continuously.
THIS IS WHY THE PULSE CAN BE FELT: the arterial wall expands with each surge, and that expansion is what a doctor feels at the wrist. Veins, carrying blood at low and steady pressure, show no pulse at all.
IT ALSO EXPLAINS THE ARTERY’S STRUCTURE: thick, muscular and ELASTIC walls are needed to withstand the surge and to smooth it out between beats. And because the pressure is high, blood cannot flow backwards — which is why arteries need NO valves, while veins do.