What type of blood flow is characterized by a constant speed across the vessel?

The type of blood flow characterized by a constant speed across the vessel is known as plug flow. In plug flow, the velocity profile is uniform across the cross-section of the blood vessel, meaning that all the blood particles travel at essentially the same speed. This type of flow is often observed in larger diameter vessels or in situations where the flow is high and consistent, such as during rapid blood transit.

Plug flow is distinct from laminar flow, where the velocity varies with distance from the vessel wall, and from turbulent flow, which is characterized by chaotic and irregular movement of the blood. Pulsatile flow is also different, as it is indicative of varying blood velocity that corresponds to the heartbeat, with acceleration and deceleration occurring during the cardiac cycle. Thus, plug flow stands out for its characteristic of maintaining a constant speed across the entire cross-section of the vessel.