Trace Carbon dioxide from the time it is in superior vena cava until exhaled through nose?

1. Superior vena cava: Carbon dioxide (CO2) is transported from the tissues to the lungs via the superior vena cava, which is one of the two large veins that carry blood back to the heart.

2. Right atrium: The superior vena cava empties into the right atrium of the heart.

3. Tricuspid valve: The right atrium contracts, pumping the blood containing CO2 through the tricuspid valve into the right ventricle.

4. Pulmonary valve: The right ventricle contracts, pumping the blood containing CO2 through the pulmonary valve into the pulmonary artery.

5. Pulmonary capillaries: The pulmonary artery branches into smaller and smaller vessels until it reaches the pulmonary capillaries, which are tiny blood vessels that surround the air sacs (alveoli) of the lungs.

6. Diffusion: In the pulmonary capillaries, CO2 diffuses from the blood into the alveoli. This is because the concentration of CO2 in the alveoli is lower than the concentration of CO2 in the blood.

7. Exhalation: The lungs exhale the air containing CO2. This is done by the contraction of the diaphragm and the intercostal muscles, which increase the volume of the thoracic cavity and force the air out of the lungs.