Which muscle separates the lungs from the abdominal organs and aids in respiration?

The diaphragm is a dome-shaped muscle located at the base of the thoracic cavity, separating the lungs from the abdominal organs. It plays a crucial role in respiration by contracting and flattening during inhalation, which increases the volume of the thoracic cavity and allows air to be drawn into the lungs. When it relaxes during exhalation, the diaphragm returns to its dome shape, helping to expel air from the lungs. This muscle is essential for efficient breathing and is primarily controlled by the phrenic nerve, which coordinates its movements with the respiratory cycle.

The other muscles listed have different functions unrelated to the direct mechanics of breathing. The rectus abdominis, for instance, is involved in flexing the trunk and plays a role during forced exhalation, but it does not primarily aid in the inhalation process. The trapezius primarily functions in the movement of the shoulders and neck, while the serratus anterior works in conjunction with the scapula, but neither influences the separation of the thoracic and abdominal cavities or directly supports respiration in the way the diaphragm does.