Advanced Emergency Medical Technician (AEMT) Practice Test

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Prepare for your Advanced Emergency Medical Technician (AEMT) exam. Study using flashcards and rich question sets with detailed explanations to enhance your readiness and confidence for the test day.

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What substance keeps alveoli in the lungs open?

Tidal volume
Capillary sphincters
Expiratory pressure
Surfactant

The correct answer is: Surfactant

Surfactant is a critical substance produced by the cells lining the alveoli in the lungs. Its primary function is to reduce surface tension within the alveoli, which are the small air sacs where gas exchange occurs. By decreasing surface tension, surfactant prevents the alveoli from collapsing, particularly during exhalation when the lungs are at their smallest volume. This is essential for maintaining the stability of the alveoli and ensuring that they remain open and available for gas exchange with the bloodstream. Without sufficient surfactant, the alveoli would collapse (a condition known as atelectasis) and would not function properly, leading to impaired oxygenation of the blood. The other choices pertain to other aspects of the respiratory process but do not directly contribute to keeping the alveoli open. While tidal volume refers to the volume of air inhaled and exhaled during normal breathing, it does not influence the structural integrity of the alveoli. Capillary sphincters are involved in the regulation of blood flow in capillaries but do not have a role in maintaining alveolar structure. Expiratory pressure relates to the pressure during exhalation but likewise does not serve the specific function of preventing alveolar collapse.