Blood vessel Discussion Board

Introduction: Blood vessels are the channels or conduits through which blood is distributed to body tissues. The cardiovascular system depends on factors such as flow and pressure to efficiently pump blood through the cardiovascular system.
For this post, you will:

Choose one factor that affects blood flow or capillary exchange: e.g., Pressure, Resistance, Mean Arterial Pressure (MAP), Vessel length, Vessel diameter, Valves, Cardiac output, Skeletal muscle activity, Respiration, Compliance, Presence of a thrombus, Blood viscosity, Blood volume, Osmotic pressure, or Net Filtration Pressure (NFP).
Describe how your choice either increases or decreases blood flow or capillary exchange under normal conditions. Note that you should select only increase OR decrease and not both.
Provide one example of a situation where either flow or exchange is not normal and how your factor could be involved.
Describe a situation (even if imaginary) that could influence blood flow or capillary exchange specifically due to your factor. Describe whether it would make flow or exchange go up or down, and in which vessels.