Changes

==Breathing==

==Breathing==

While breathing, an organism's diaphragm contracts and flattens out. This allows it to move down, so the lungs have more room to grow larger as they fill up with air. The diaphragm isn't the only part that gives your lungs the room they need. Your rib muscles also lift the ribs up and outward to give the lungs more space. Simultaneously, you inhale air through your mouth and nose, and the air heads down your trachea. On the way down the windpipe, tiny hairs called cilia move gently to keep mucus and dirt out of the lungs. The air then goes through the series of branches in your lungs, through the bronchi and the bronchioles. The air finally ends up in the 600 million alveoli. As these millions of alveoli fill up with air, the lungs get bigger. The alveoli allow [[oxygen]] from the air to pass into your [[blood]]. All the cells in the body need oxygen every minute of the day. Oxygen passes through the walls of each alveolus into the tiny capillaries that surround it. The oxygen enters the blood in the tiny capillaries, hitching a ride on [[red blood cell]]s and traveling through layers of blood vessels to the [[heart]]. The heart then sends the oxygenated blood out to all the cells in the body.

While breathing, an organism's diaphragm contracts and flattens out. This allows it to move down, so the lungs have more room to grow larger as they fill up with air. The diaphragm isn't the only part that gives your lungs the room they need. Your rib muscles also lift the ribs up and outward to give the lungs more space. Simultaneously, you inhale air through your mouth and nose, and the air heads down your trachea. On the way down the windpipe, tiny hairs called cilia move gently to keep mucus and dirt out of the lungs. The air then goes through the series of branches in your lungs, through the bronchi and the bronchioles. The air finally ends up in the 600 million alveoli. As these millions of alveoli fill up with air, the lungs get bigger. The alveoli allow [[oxygen]] from the air to pass into your [[blood]]. All the cells in the body need oxygen every minute of the day. Oxygen passes through the walls of each alveolus into the tiny capillaries that surround it. The oxygen enters the blood in the tiny capillaries, hitching a ride on [[red blood cell]]s and traveling through layers of blood vessels to the [[heart]]. The heart then sends the oxygenated blood out to all the cells in the body.