Oxygen and blood flow description
First, you inhale through your mouth and nose. The air travels past the epiglottis and into the trachea before splitting into the bronchi. The bronchi go to the lungs and the bronchioles. At the end of the bronchioles are the alveoli. These are small air sacks; this is where gaseous exchange happens. Gaseous exchange is when oxygen goes into the blood and carbon dioxide diffuses out of the blood. The carbon dioxide goes into the alveoli. ...view middle of the document...
First it enters the left atrium, before passing through the bicuspid valve into the left ventricle. The bicuspid valve opens as there is a build up of pressure because of the atrium having oxygen rich blood in it. It then travels out of the aorta to the body.
At the muscles the oxygen is transferred from the blood to the muscles. The oxygen diffuses into the muscles and the waste gases such as carbon dioxide diffuse out of the muscles into the blood supply.
The deoxygenated blood travels back to the heart through the vena cava. First, it enters the right atrium, before passing through the tricuspid valve and into the right ventricle. It is then pumped out of the pulminary artery, through the pulminary valve, to collect more oxygen from the lungs and to discard the carbon dioxide produced during the process of respiration.
When you exhale(breath out), the carbon dioxide travels into the alveoli from where there is lots of carbon dioxide into the capillaries where there is not much of carbon dioxide in the alveoli. It then enters the bronchioles, into the bronchus, into the trachea and finally out through the nose and mouth.