What nerve is responsible for innervating the diaphragm?

• A. Vagus Nerve
• B. Phrenic Nerve
• C. Intercostal Nerves
• D. Accessory Nerve

Answer: (B)

The diaphragm is a crucial muscle in respiration, and it is primarily innervated by the phrenic nerve. This nerve arises from the cervical spinal roots, specifically from C3 to C5. It travels down into the thorax and provides motor innervation to the diaphragm, enabling it to contract and facilitate breathing.

The phrenic nerve's anatomical relationship to the diaphragm makes it uniquely suited for this function, as it directly stimulates the muscle fibers of the diaphragm to contract during inhalation. This contraction lowers the diaphragm, increasing the volume of the thoracic cavity and allowing air to flow into the lungs.

Other nerves, such as the vagus nerve and intercostal nerves, play roles in broader respiratory or thoracic functions but do not innervate the diaphragm directly. The vagus nerve is primarily involved in parasympathetic control of the lungs and heart, while intercostal nerves mainly innervate the intercostal muscles, which assist in the mechanics of breathing but do not have a motor function in the diaphragm. The accessory nerve primarily innervates muscles involved in shoulder movement and is not involved with the diaphragm.

Thus, the phrenic nerve is the correct answer due to its specific role in innervating the diaphragm