Final answer:
Blood vessels arranged in parallel ensure the same flow through each vessel with a total peripheral resistance of 1, allowing effective regulation of blood flow and substance exchange in the capillaries.
Step-by-step explanation:
When the blood vessels are arranged in parallel, the flow of blood through each blood vessel is the same, and the total peripheral resistance is usually 1. The circulatory system regulates blood flow by changes in vessel size and blood pressure, where arterioles act as resistance vessels. Larger vessels branch into smaller ones, increasing the total cross-sectional area and reducing blood velocity to facilitate substance exchange with cells in the capillaries.