Why are elastic arteries sometimes called conducting arteries and what happens when they become hardened?

Elastic arteries are called conducting arteries because their large lumens create low-resistance pathways that conduct blood from the heart to the medium-sized arteries. When they become hardened, as in arteriosclerosis, they cannot recoil to maintain pressure, so blood flows more intermittently. This also exposes arterial walls throughout the body to higher pressures, which can weaken them, leading to aneurysms or rupture.

Elastic arteries, such as the aorta and its major branches, are thick-walled arteries near the heart. They have the largest diameters of any arteries and contain more elastin than other vessel types, especially in the tunica media. Because their large lumens offer low resistance, they act as conducting arteries by providing a smooth, low-resistance pathway that carries blood from the heart onward to medium-sized muscular arteries. Functionally, they act as pressure reservoirs: they expand when the heart ejects blood and then recoil during diastole, which keeps blood flowing fairly continuously rather than in a stop-and-start manner. If these arteries become hard and unyielding due to arteriosclerosis, this pressure-smoothing effect is lost. Blood flow becomes intermittent, like water flowing through a stiff garden hose when the faucet is turned on and off. Additionally, without elastic recoil to dampen pressure changes, the walls of arteries throughout the body experience higher pressures. These chronically high pressures can weaken arterial walls, causing them to balloon out as an aneurysm or even burst.