BIO 251 LATEST 2026 EXAM QUESTIONS AND ANSWERS
GUARANTEE A+
✔✔What are the three tunics of blood vessels? - ✔✔Tunica interna (endothelium),
tunica media (smooth muscle), tunica externa (connective tissue, vasa vasorum).
✔✔Conducting (elastic) arteries function? - ✔✔Stretch and recoil to maintain pressure
during cardiac cycle.
✔✔Distributing (muscular) arteries? - ✔✔Distribute blood to organs; have
internal/external elastic lamina.
✔✔Arterioles? - ✔✔Major resistance vessels controlling BP via diameter.
✔✔What are arterial sense organs? - ✔✔Carotid sinuses (BP), carotid bodies
(pH/CO₂/O₂), aortic bodies (chemicals).
✔✔Types of capillaries? - ✔✔Continuous (tight), fenestrated (pores), sinusoidal (large
gaps).
✔✔Precapillary sphincters function? - ✔✔Control blood flow into capillary beds
(vasomotion).
✔✔Why are veins called capacitance vessels? - ✔✔Hold majority of blood volume at
rest.
✔✔Function of venous valves? - ✔✔Prevent backflow.
✔✔What is pulse pressure and MAP? - ✔✔PP = systolic − diastolic; MAP = average
arterial pressure.
✔✔What determines resistance? - ✔✔Length, diameter (most important), turbulence.
✔✔Vasodilation vs vasoconstriction? - ✔✔Widening of blood vessels vs narrowing of
blood vessels
✔✔Mechanisms of venous return? - ✔✔Gravity, muscular pump, respiratory pump.
✔✔Filtration vs reabsorption? - ✔✔Filtration = fluid out (hydrostatic pressure),
reabsorption = fluid in (oncotic pressure).
✔✔What is oncotic pressure? - ✔✔Pulling force due to plasma proteins (esp. albumin).
GUARANTEE A+
✔✔What are the three tunics of blood vessels? - ✔✔Tunica interna (endothelium),
tunica media (smooth muscle), tunica externa (connective tissue, vasa vasorum).
✔✔Conducting (elastic) arteries function? - ✔✔Stretch and recoil to maintain pressure
during cardiac cycle.
✔✔Distributing (muscular) arteries? - ✔✔Distribute blood to organs; have
internal/external elastic lamina.
✔✔Arterioles? - ✔✔Major resistance vessels controlling BP via diameter.
✔✔What are arterial sense organs? - ✔✔Carotid sinuses (BP), carotid bodies
(pH/CO₂/O₂), aortic bodies (chemicals).
✔✔Types of capillaries? - ✔✔Continuous (tight), fenestrated (pores), sinusoidal (large
gaps).
✔✔Precapillary sphincters function? - ✔✔Control blood flow into capillary beds
(vasomotion).
✔✔Why are veins called capacitance vessels? - ✔✔Hold majority of blood volume at
rest.
✔✔Function of venous valves? - ✔✔Prevent backflow.
✔✔What is pulse pressure and MAP? - ✔✔PP = systolic − diastolic; MAP = average
arterial pressure.
✔✔What determines resistance? - ✔✔Length, diameter (most important), turbulence.
✔✔Vasodilation vs vasoconstriction? - ✔✔Widening of blood vessels vs narrowing of
blood vessels
✔✔Mechanisms of venous return? - ✔✔Gravity, muscular pump, respiratory pump.
✔✔Filtration vs reabsorption? - ✔✔Filtration = fluid out (hydrostatic pressure),
reabsorption = fluid in (oncotic pressure).
✔✔What is oncotic pressure? - ✔✔Pulling force due to plasma proteins (esp. albumin).
