the lungs

• oxygen is needed in your bloodstream to supply your cells with respiration, as well as getting rid of carbon dioxide from the blood
• the lungs are in the thorax, which is in the top part of your body. its seperated from the lower part of the body by the diaphragm
• the lungs are like big pink sponges and are protected by the ribcage. they're surrounded by the plural membrane
• the air that you breathe in goes through the trachea. this splits into two tubes called bronchi, one going to each lung
• the bronchi split into progressively smaller tubes called bronchioles
• the bronchioles finally end at small bags called alveoli where the gas exchange takes place
• the lungs contain millions and millions of little air sacs called alveoli, surrounded by a network of blood capillaries. this is where gas exchange happens
• the blood passing next to the alveoli has just returned to the lungs from the rest of the body, so it contains lots of carbon dioxide and very little oxygen. oxygen diffuses out of the alveolus into the blood. carbon dioxide diffuses out of the blood into the alveolus to be breathed out
• when the blood reaches body cells oxygen is released from the red blood cells and diffuses into the body cells
• carbon dioxide diffuses out of the body cells into the blood. it's then carried back to the lungs