Carbon dioxide is primarily removed from the body through the respiratory system, specifically via the lungs.
Here's a more detailed breakdown of the process:
- Cellular Respiration: Cells throughout the body produce carbon dioxide as a waste product of metabolism (cellular respiration).
- Transport in the Blood: Carbon dioxide travels from the cells through the bloodstream to the lungs in a few different forms:
- Dissolved in plasma (about 7-10%)
- Bound to hemoglobin (the protein in red blood cells) as carbaminohemoglobin (about 20%)
- Converted to bicarbonate ions (HCO3-) within red blood cells, a process that involves the enzyme carbonic anhydrase (about 70%).
- The Role of the Lungs: When carbon dioxide-rich blood reaches the lungs:
- The bicarbonate ions are converted back into carbon dioxide.
- Carbon dioxide detaches from hemoglobin.
- Carbon dioxide dissolved in the plasma diffuses into the alveoli (tiny air sacs in the lungs).
- Exhalation: During exhalation, the carbon dioxide in the alveoli is expelled from the body.
Essentially, the respiratory system works in reverse of oxygen intake: oxygen is inhaled and transported to cells, while carbon dioxide is collected from cells and exhaled.
Simplified Steps:
- Cells produce carbon dioxide.
- Carbon dioxide enters the bloodstream.
- Blood carries carbon dioxide to the lungs.
- Carbon dioxide moves from blood into the air sacs (alveoli) of the lungs.
- Carbon dioxide is exhaled from the body.
