▁cap ill aries ▁in ▁the ▁circul atory ▁system . ▁ ▁In ▁the ▁ar ter i oles ▁blood ▁pressure ▁is ▁lower ▁than ▁in ▁the ▁major ▁ar ter ies . ▁This ▁is ▁due ▁to ▁b if ur c ations , ▁which ▁cause ▁a ▁drop ▁in ▁pressure . ▁The ▁more ▁b if ur c ations , ▁the ▁higher ▁the ▁total ▁cross - section al ▁area , ▁therefore ▁the ▁pressure ▁across ▁the ▁surface ▁dro ps . ▁This ▁is ▁why ▁the ▁ar ter i oles ▁have ▁the ▁highest ▁pressure - drop . ▁The ▁pressure ▁drop ▁of ▁the ▁ar ter i oles ▁is ▁the ▁product ▁of ▁flow ▁rate ▁and ▁resistance : ▁ ∆ P = Q ▁x res istance . ▁The ▁high ▁resistance ▁observed ▁in ▁the ▁ar ter i oles , ▁which ▁factor ▁largely ▁in ▁the ▁ ∆ P ▁is ▁a ▁result ▁of ▁a ▁smaller ▁radius ▁of ▁about ▁ 3 0   µ m . ▁The ▁smaller ▁the ▁radius ▁of ▁a ▁t ube , ▁the ▁larger ▁the ▁resistance ▁to ▁fluid ▁flow . ▁ ▁Im medi ately ▁following ▁the ▁ar ter i oles ▁are ▁the ▁cap ill aries . ▁Following ▁the ▁logic ▁observed ▁in ▁the ▁ar ter i oles , ▁we ▁expect ▁the ▁blood ▁pressure ▁to ▁be ▁lower ▁in ▁the ▁cap ill aries ▁compared ▁to ▁ ▁the ▁ar ter i oles . ▁Since ▁pressure ▁is ▁a ▁function ▁of ▁force ▁per ▁unit ▁area , ▁( P   =   F / A ), ▁the ▁larger ▁the ▁surface ▁area , ▁the ▁less er ▁the ▁pressure ▁when ▁an ▁external ▁force ▁acts ▁on ▁it