Final answer:
The term for lumen size, where larger numbers denote smaller lumens, is Diameter. Lumen diameter drastically affects resistance within blood vessels, and a smaller cellular radius typically indicates a smaller surface area-to-volume ratio, which is important in cell biology.
Step-by-step explanation:
The term that refers to lumen size, with larger numbers indicating smaller lumen sizes, is Diameter (A). In biological and medical contexts, lumen refers to the inside space of a tubular structure, such as a blood vessel or the intestine. The influence of lumen diameter on resistance is significant. For instance, a slight decrease in the diameter of a blood vessel drastically increases the resistance to blood flow due to the relationship expressed as R = 1/r4, where R is resistance and r is the radius of the blood vessel.
Furthermore, when comparing two cells, if cell B has a smaller radius than cell A, it likely has a smaller surface area-to-volume ratio. This concept is critical in cell biology, as the surface area-to-volume ratio can influence the cell's ability to exchange materials with its surroundings.