What: "The circulatory system is like a network of one-way streets. If blood started flowing the wrong way, the blood gases (oxygen and carbon dioxide) might mix, causing a serious threat to your body. In the lungs, capillaries on the outside of the alveoli exchange carbon dioxide and oxygen. Fresh, oxygen-rich blood enters the pulmonary veins and then returns to the heart, re-entering through the left atrium. "

Writer: stevewest

LCC:

Where: Reference Link Has Evaporated

Date: Jun 11 2014 5:30 PM