Final answer:
The statement regarding venipuncture needle gauge size is true; smaller gauge numbers mean larger needle lumens. Veins are characterized by thin walls, large lumens, low pressure, and the presence of valves. The lumen size dramatically affects flow and resistance in blood vessels.
Step-by-step explanation:
The statement that the smaller the gauge number of a venipuncture needle, the larger the lumen is true. Needle gauges run inversely to their diameter; thus, a 16-gauge needle has a larger lumen than a 22-gauge needle. This is significant because it affects the flow rate of fluids, with larger-lumen needles allowing greater flow rates, which is critical in medical situations such as venipuncture where the viscosity of drawn blood can play a role.
With respect to veins, the true description is that they have thin walls, large lumens, low pressure, and have valves. This structural design facilitates the return of blood to the heart against the force of gravity and with minimal pressure. Veins differ from arteries, which have thicker walls due to the higher pressures they must withstand as blood is pumped directly from the heart.
The influence of lumen diameter on resistance is dramatic and is governed by the principle that resistance is inversely proportional to the fourth power of the radius of the blood vessel. This means slight changes in diameter cause significant changes in resistance and flow, explaining why veins have larger lumens to provide less resistance to blood flow.