Why do arteries need to be thick, muscular, and elastic?
to make our bodies strong for movement
to withstand the pressure of the blood that is being pumped by the heart
to pull the blood back to the heart from all areas of the body
to withstand changes in blood temperature

when you breathe in, or inhale, your diaphragm contracts (tightens) and moves downward. this increases the space in your chest cavity, into which your lungs expand. the intercostal muscles between your ribs also enlarge the chest cavity. they contract to pull your rib cage both upward and outward when you inhale.