The major nerve of the cervical plexus that innervates the diaphragm is the
(a) Median nerve
(b) Axillary nerve
(c) Phrenic nerve
(d) Common fibular nerve

Verified step by step guidance

Step 1: Understand the anatomy of the cervical plexus, which is a network of nerves formed by the anterior rami of the first four cervical spinal nerves (C1-C4). It primarily innervates muscles and skin of the neck and upper shoulder region.

Step 2: Identify the major nerves that arise from the cervical plexus. Among these, the phrenic nerve is notable because it originates mainly from the C3, C4, and C5 spinal nerves.

Step 3: Recall the function of the phrenic nerve, which is to provide motor innervation to the diaphragm, the primary muscle responsible for breathing.

Step 4: Compare the options given: the median nerve and axillary nerve are associated with the brachial plexus and innervate upper limb muscles, while the common fibular nerve is part of the sacral plexus and innervates parts of the lower leg.

Step 5: Conclude that the phrenic nerve is the major nerve of the cervical plexus that innervates the diaphragm, making option (c) the correct choice.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Cervical Plexus

The cervical plexus is a network of nerves formed by the anterior rami of the first four cervical spinal nerves (C1-C4). It provides sensory and motor innervation to parts of the neck, shoulders, and diaphragm. Understanding its structure is essential to identify which nerves arise from it.

Phrenic Nerve

The phrenic nerve originates mainly from the C3-C5 spinal nerves within the cervical plexus. It is the primary motor nerve that innervates the diaphragm, enabling breathing by controlling diaphragm contractions. Recognizing its role is key to answering the question.

Diaphragm Innervation

The diaphragm is the main muscle responsible for respiration. Its innervation is crucial for its function, and the phrenic nerve is the major nerve supplying it. Other nerves listed (median, axillary, common fibular) do not innervate the diaphragm.

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