Which of the following nerve carries fibres 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, specifically from the **C5 to T1 nerve roots**. It plays a crucial role in providing motor and sensory innervation to the upper limb. The question is testing the understanding of the anatomical structure and organization of the brachial plexus.
**Why the Correct Answer is Right**
The **median nerve** is formed from contributions of all the roots of the brachial plexus (C5 to T1), although the primary contributions come from **C6, C7, C8, and T1**. It is responsible for innervating muscles of the anterior forearm and thenar eminence, as well as providing sensory innervation to the palmar aspect of the thumb, index, middle finger, and the radial half of the ring finger.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because it does not receive contributions from all roots.
**Option B:** Incorrect as it primarily arises from the **C5 and C6 roots**.
**Option D:** Incorrect because it mainly originates from the **C8 and T1 roots**.
**Clinical Pearl / High-Yield Fact**
A key point to remember is that injuries to the brachial plexus can result in varying degrees of neurological deficit, depending on which roots are affected. The **median nerve**, due to its widespread root contributions, is often implicated in these injuries.
**Correct Answer:** D. Median nerve.