What is the biological meaning of the slow movement of blood through the capillaries?

Blood flows slowly through the capillaries. This is of great biological importance. Due to this feature, the cells are saturated with oxygen. Also, the bonds of hemoglobin with oxygen have time to change into bonds with carbon dioxide for its further removal from the body. If the blood moved quickly through the capillaries, then the exchange of molecules would be ineffective, but it still took place. A decrease in the rate of passage of blood is provided by a small diameter of the capillary and their large number in the body.