Which of the following actions follows inhalation? a. The...

Which of the following actions follows inhalation?
a. The epiglottis closes.
b. The diaphragm relaxes.
c. Surfactants are released into the alveoli.
d. The diaphragm and intercostal muscles contract.

Key Concepts

Respiratory Cycle

The respiratory cycle is the complete process of breathing involving inhalation and exhalation. During inhalation, air is drawn into the lungs primarily through the active contraction of muscles such as the diaphragm and intercostal muscles. Exhalation follows as these muscles relax, allowing air to be expelled from the lungs, maintaining a continuous flow of fresh air for gas exchange.

Diaphragm Function

The diaphragm is a crucial muscle in the mechanics of breathing. It contracts and flattens during inhalation to enlarge the thoracic cavity and lower the internal pressure, permitting air to enter the lungs. After inhalation, the diaphragm relaxes, which helps reduce the lung volume and increases pressure to drive exhalation.

Exhalation Mechanics

Exhalation is the phase that immediately follows inhalation in the respiratory cycle. It is primarily a passive process that occurs as the diaphragm and intercostal muscles relax, allowing the elastic recoil of the lungs and chest wall to expel air. This relaxation is essential in maintaining the rhythm and efficiency of continuous breathing.

Alveolar Surfactant Function

Alveolar surfactants are substances secreted by the alveolar cells to reduce surface tension within the alveoli, preventing collapse and aiding in maintaining lung stability. Their release is associated with alveolar stretch during inhalation, ensuring that the alveoli remain open and efficient for gas exchange during both inhalation and exhalation.

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