Regarding the branches and terminal nerves of the brachial plexus, all of the following statements are correct EXCEPT:

## Analysis of Brachial Plexus Terminal Branches ### Correct Statements **Option A — Radial Nerve (Posterior Cord):** True. The radial nerve is the largest and most important terminal branch of the posterior cord. It arises from C5–C8 and T1 and is the direct continuation of the posterior cord in the axilla. **Option C — Median Nerve Formation:** True. The median nerve is formed by the union of the lateral cord (from the anterior divisions of the superior and middle trunks) and the medial cord (from the anterior division of the inferior trunk) at the level of the axilla. **Option D — Ulnar Nerve Origin:** True. The ulnar nerve arises as the terminal branch of the medial cord. It receives no contribution from the lateral cord; it is purely a medial cord derivative. ### The Incorrect Statement (Correct Answer) **Option B — Musculocutaneous Nerve and Biceps Innervation:** FALSE. While the musculocutaneous nerve (from the lateral cord) does innervate the biceps brachii, it innervates only the **short and long heads** of biceps. The **short head of biceps receives dual innervation** from both the musculocutaneous nerve AND the median nerve (via the lateral pectoral branch in some anatomical variants, or more commonly via musculocutaneous alone). However, the critical error is that the musculocutaneous nerve does NOT innervate **all three heads**—there is no "third head" of biceps brachii in standard anatomy. Biceps has only two heads (short and long). The statement is anatomically inaccurate. **Key Point:** The musculocutaneous nerve innervates: - Biceps brachii (both heads) - Brachialis - Brachioradialis (via continuation as the lateral antebrachial cutaneous nerve) **High-Yield:** Remember the **"3 C's" of the lateral cord**: **C**oracobrachialis, **C**ephalic nerve (sensory), **C**ontinuation as musculocutaneous. ### Summary Table: Terminal Branches of Brachial Plexus | Terminal Branch | Parent Cord | Key Innervations | Root Value | | --- | --- | --- | --- | | Radial | Posterior | Triceps, extensors of forearm/wrist, dorsal skin | C5–C8, T1 | | Axillary | Posterior | Deltoid, teres minor, shoulder joint | C5–C6 | | Musculocutaneous | Lateral | Biceps (2 heads), brachialis, brachioradialis | C5–C7 | | Median | Lateral + Medial | Pronators, flexors (forearm/wrist), thenar muscles | C5–C8, T1 | | Ulnar | Medial | Intrinsic hand muscles, medial forearm flexors | C8–T1 | **Mnemonic — Terminal Branches (MARUM):** **M**edian, **A**xillary, **R**adial, **U**lnar, **M**usculocutaneous.