the lungs

• the lungs are in the thorax
• the thorax is the top part of the body
• the thorax is separated from the lower part of the body by the diaphragm
• inhaled air goes through the trachea
• the trachea splits into two tubes called bronchi
• the bronchi split into bronchioles
• bronchioles split into alveoli
• the alveoli are the site of gas exchange in the lungs
• the lungs contain million of alveoli, which are surrounded by a newtork of capillaries
• blood passing next to the alveoli contains a lot of carbon dioxide and little oxygen. oxygen diffuses out of the alveolus into the blood through diffusion. carbon dioxide diffuses out of the blood into the alveolus
• when blood reaches body cells, oxygen is released from the red blood cells and diffuses into the body cells
• carbon dioxide diffuses out of body cells, into the blood