Pressure, flow and velocity of blood

Total blood flow (L/min) is equal in all areas of the vascular circuit (arterial, capillary, venous) yet the velocity of flow (mm/s) is inversely proportional to the total cross sectional area of each region. This generates flow velocity that is very high in the aorta and large veins, yet very much slower in the capillaries which have an enormous total cross sectional area. This is, of course, adaptive to the need for capillary exchange in these very short vessels.

[@pranavbarla4635]

thank you, this was very helpful

[@mechanismsandlogicinhumanp5840]

Glad to hear it!

[@theprince9636]

As we see in vena cava flow rate is high then why it has low blood pressure?

[@mechanismsandlogicinhumanp5840]

Total energy of the blood falls, including its pressure, due to resistance along the vascular tree. The resistance is largely friction with the vessel walls and the energy is lost as heat. As the vena cava are farthest from the initial pressurization of blood at the heart, the pressure there is very low. Also, according to Bernoulli's equation, due to conservation of energy, as the cross sectional area falls and velocity increases in the large veins (coming from the large total cross sectional area of the capillaries), the pressure must fall to compensate (swapping potential energy for kinetic, essentially)