The heart is part of the cardiovascular system, not the respiratory system.

The respiratory system is responsible for the exchange of oxygen and carbon dioxide between the body and the environment.

The pectoralis major is a chest muscle, not a respiratory muscle.

Inspiration is the process of taking air into the lungs.

Expiration is the process of releasing air from the lungs.

The alveoli are small air sacs in the lungs where gas exchange takes place.

Helium is not a respiratory gas, as it is not involved in gas exchange.

The partial pressure of oxygen in the alveoli is approximately 100 mmHg.

The partial pressure of carbon dioxide in the alveoli is approximately 40 mmHg.

Hemoglobin is the protein in red blood cells that transports oxygen from the lungs to the tissues.

Carbon dioxide is a waste product of cellular metabolism that is transported from the tissues to the lungs for exhalation.

The respiratory center in the medulla oblongata is responsible for controlling the rate and depth of breathing.

The carotid bodies are small clusters of cells located near the carotid arteries that sense changes in blood oxygen levels.

The aortic bodies are small clusters of cells located near the aorta that sense changes in blood carbon dioxide levels.

Respiratory regulation is the process of adjusting the rate and depth of breathing in response to changes in blood gas levels.