What metabolic waste excreted through the lungs?

The primary metabolic waste excreted through the lungs is carbon dioxide (CO2). During cellular respiration, the body converts glucose and other nutrients into energy, releasing carbon dioxide as a by-product. The circulatory system transports CO2 from the tissues to the lungs, where it is exhaled during the breathing process.

Here's a more detailed explanation:

1. Cellular Respiration: Cellular respiration is a series of metabolic reactions that take place within the cells to produce energy in the form of adenosine triphosphate (ATP). During this process, glucose (a sugar obtained from food) is broken down in the presence of oxygen to produce energy, water (H2O), and carbon dioxide (CO2).

2. Transport of CO2: Once produced in the cells, carbon dioxide diffuses into the bloodstream and is carried by the circulatory system to the lungs. Hemoglobin, a protein present in red blood cells, plays a vital role in transporting the majority of CO2 from tissues to the lungs.

3. Gas Exchange in the Lungs: The lungs are the primary organs responsible for gas exchange in the respiratory system. When we inhale, oxygen from the air enters the lungs, while carbon dioxide moves out. This exchange occurs in the alveoli, tiny air sacs in the lungs.

4. Exhalation: After the gas exchange, carbon dioxide is expelled from the lungs during the process of exhalation. The diaphragm and other respiratory muscles contract, pushing the carbon dioxide-rich air out of the lungs through the nose or mouth.

In summary, carbon dioxide is the primary metabolic waste excreted through the lungs during the process of respiration. The body's circulatory and respiratory systems work together to transport CO2 from the cells to the lungs, where it is released into the atmosphere during exhalation.