Which of the following nerve carries fibers from all the roots of brachial plexus?
**Core Concept**
The brachial plexus is a complex network of nerves that originates from the spinal cord in the neck, providing motor and sensory innervation to the upper limb. The nerves of the brachial plexus arise from the ventral rami of spinal nerves C5-T1, which form a plexus of interconnected nerves.
**Why the Correct Answer is Right**
The musculocutaneous nerve (C5-C7) and the median nerve (C5-T1) both receive contributions from the brachial plexus, but the musculocutaneous nerve is primarily a motor nerve, whereas the median nerve carries both motor and sensory fibers. However, the median nerve is the primary nerve that carries fibers from all the roots of the brachial plexus, including C5-T1. This is because the median nerve is formed by the union of the lateral and medial cords of the brachial plexus, which in turn receive contributions from all the roots of the plexus.
**Why Each Wrong Option is Incorrect**
* **Option A:** The axillary nerve (C5-C6) primarily carries fibers from the posterior cord of the brachial plexus and is not a primary nerve that carries fibers from all the roots of the plexus.
* **Option B:** The radial nerve (C5-T1) carries fibers from the posterior cord of the brachial plexus, but it is not the primary nerve that carries fibers from all the roots of the plexus.
* **Option D:** The ulnar nerve (C8-T1) carries fibers from the medial cord of the brachial plexus, but it is not the primary nerve that carries fibers from all the roots of the plexus.
**Clinical Pearl / High-Yield Fact**
The brachial plexus is often injured in cases of traumatic shoulder injury, such as a shoulder dislocation or fracture, which can result in numbness, weakness, or paralysis of the upper limb.
**Correct Answer:** C.