What effect do viscous blood and turbulent blood have on resistance?

• A. They decrease resistance
• B. They cause no change
• C. They increase resistance (directly proportional)
• D. They cause unpredictable changes

Answer: (C)

Higher viscosity and turbulent flow both raise the energy losses as blood moves through vessels, so they increase resistance. In laminar flow, resistance rises with viscosity because of Poiseuille’s law: R is proportional to viscosity (R ∝ η L / r^4). So, thicker blood directly makes it harder for the same flow to occur. When flow becomes turbulent, chaotic eddies and intermixing create additional friction and energy dissipation, causing a larger pressure drop for the same flow. Together, these factors push resistance upward, which is why the best choice says resistance increases (and, in the viscosity case, directly proportional). The other options don’t fit because higher viscosity and turbulence do not reduce resistance, leave it unchanged, or produce unpredictable results.