Questions
1. How are weather fronts important to describing air masses?

answer; the tunica intima also called tunica interna, consists of elastic fibers,connective tissue and smooth muscle cells;

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.