Learning goal 2: Select all of the options that best complete the following sentence. When we exhale:

When we exhale, we are releasing air from our lungs. This process is a crucial part of the respiratory system and involves several physiological actions. Specifically:

1. Carbon Dioxide Removal: Exhaling allows the body to remove carbon dioxide, a waste product of metabolism, from the bloodstream.
2. Muscle Relaxation: The diaphragm and intercostal muscles (muscles between the ribs) relax during exhalation. This relaxation helps the thoracic cavity to decrease in volume, pushing air out of the lungs.
3. Air Composition Change: The air we exhale contains a higher concentration of carbon dioxide and water vapor compared to the air we inhale, which is primarily composed of oxygen and nitrogen.
4. Overall Regulation of Breathing: Exhalation plays a vital role in maintaining the balance of oxygen and carbon dioxide in the body, thus helping to regulate blood pH and ensure proper cellular function.

In summary, exhaling is not just about sending out air; it's an essential biological function that supports metabolic processes and homeostasis in the body.