Veins... A) operate under high pressure
B) branch into smaller vessels called arterioles
C) often have valves to prevent the back flow of blood

name and explain one of the event that occurs during meiosis that increases the variation in offspring even more than simple reproduction?

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.