Nerve supplying to diaphragm

Appeared in: VSSC Nursing Officer - 2021

Explanation

The phrenic nerve provides the sole motor innervation to the diaphragm, the chief muscle of respiration.
It originates from the cervical spinal roots C3, C4, and C5, a fact summarized by the mnemonic 'C3, 4, 5 keeps the diaphragm alive'.
Besides motor functions, the phrenic nerve also carries sensory information from the central part of the diaphragm.

Option A: The vagus nerve provides parasympathetic innervation to thoracic and abdominal organs. While it passes through the diaphragm, it does not provide motor supply for respiration.
Option C: The glossopharyngeal nerve is a cranial nerve involved in sensation for the posterior tongue and pharynx, and motor supply to the stylopharyngeus muscle. It has no role in diaphragm function.
Option D: Intercostal nerves supply motor function to the intercostal muscles (muscles between the ribs) and provide sensory innervation only to the peripheral (outer) part of the diaphragm.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Innervation of the Diaphragm as background academic context rather than a clinical decision trigger.
A high spinal cord injury above the C3 level can sever the connection to the phrenic nerve, leading to paralysis of the diaphragm and immediate respiratory failure, requiring mechanical ventilation.
Irritation of the phrenic nerve (e.g., from a subphrenic abscess or pleurisy) can cause 'referred pain' to the shoulder tip, as the C3-C5 spinal segments also supply sensation to this skin area.
During thoracic surgery, surgeons must be careful to identify and preserve the phrenic nerve to prevent postoperative respiratory complications.

How to Approach the Question

First, identify the key terms in the question: 'Nerve' and 'diaphragm'. The question is asking for the primary nerve supply to this specific muscle.
This is a factual recall question based on anatomical knowledge.
Recall the function of the diaphragm as the main muscle for breathing.
Evaluate each option: Vagus (thoracic/abdominal organs), Phrenic (diaphragm), Glossopharyngeal (tongue/pharynx), Intercostal (muscles between ribs).
Remember the mnemonic 'C3, 4, 5 keeps the diaphragm alive' to strongly associate the phrenic nerve with the diaphragm.
Select the option that is the primary motor nerve for the diaphragm.

Concept Tested & Keywords

QwI1zQWzIrSEdjI8ycb7l_

E6 Anatomy BDChaurasia V2 10e Part 2 p. 116-118

E6 Anatomy Applied Ashalatha 4e p. 431-433

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