To which nerve is the serratus posterior inferior muscle supplied?

The serratus posterior inferior muscle is primarily supplied by the intercostal nerve. This muscle plays a crucial role in the expiration process by aiding the downward movement of the ribs and stabilizing them during breathing. The intercostal nerves, which emerge from the thoracic spinal nerves, innervate the muscles between the ribs, providing the necessary motor function for the serratus posterior inferior to assist in respiratory mechanics.

The other nerve options do not have the appropriate relationship with the serratus posterior inferior. The vagus nerve is mostly responsible for parasympathetic control over the heart, lungs, and digestive tract, rather than muscle innervation. The erector spinae nerve does not exist as a separate entity; rather, the erector spinae muscles are innervated by the dorsal rami of spinal nerves. The spinal accessory nerve primarily innervates the sternocleidomastoid and trapezius muscles, which are unrelated to the function of the serratus posterior inferior. Therefore, understanding the intercostal nerve's role is essential for recognizing which nerves are responsible for which muscle groups in the thoracic region.