What is the definition of spontaneous ventilation?

Spontaneous ventilation refers to the natural process of breathing where air moves into and out of the lungs without assistance from mechanical devices. This definition encapsulates the fundamental physiological function of the respiratory system, which involves inhalation (the intake of air) and exhalation (the expulsion of air).

This process is essential for maintaining adequate oxygen levels in the body and for the removal of carbon dioxide, a waste product of metabolism. Spontaneous ventilation relies on the diaphragm and other respiratory muscles, making it distinct from assisted or controlled ventilation methods, where external mechanisms aid in the breathing process.

The other choices refer to specific functions related to gas exchange and gas transport within the body rather than the act of breathing itself. The exchange of oxygen and carbon dioxide between blood and tissues describes the metabolic functions of respiration, while absorption of oxygen in the alveoli and release of carbon dioxide from the blood to the lungs pertain to the gas exchange mechanism rather than the ventilation process itself.