Regarding the course and anatomical relationships of the ulnar nerve in the upper limb, all of the following statements are correct EXCEPT:

Explanation

## Anatomical Course of the Ulnar Nerve ### Origin and Upper Arm **Key Point:** The ulnar nerve is the continuation of the medial cord of the brachial plexus (C8–T1 roots). It descends along the medial aspect of the arm, passing posterior to the medial epicondyle of the humerus at the elbow. ### Forearm Course **High-Yield:** In the forearm, the ulnar nerve runs between two muscles: - **Medial:** Flexor carpi ulnaris (FCU) - **Lateral:** Flexor digitorum superficialis (FDS) The ulnar artery lies medial to the nerve initially, then crosses to run alongside it. ### Wrist and Hand Entry **Key Point:** The ulnar nerve does NOT pass through the carpal tunnel. Instead, it enters the hand by passing **superficial to the flexor retinaculum** through the **ulnar canal (Guyon's canal)**. This is a critical anatomical distinction: | Structure | Passes Through Carpal Tunnel | Passes Through Guyon's Canal | |-----------|------------------------------|------------------------------| | Median nerve | Yes (with 9 other structures) | No | | Ulnar nerve | **No** | **Yes** | | Ulnar artery | No | Yes | **Clinical Pearl:** The ulnar nerve's superficial passage through Guyon's canal makes it vulnerable to compression injuries from repetitive trauma or ganglion cysts at the wrist, but protects it from carpal tunnel syndrome (which affects the median nerve). ### Distal Division **High-Yield:** Just distal to the pisiform bone (in the palm), the ulnar nerve divides into: 1. **Superficial branch** — supplies the hypothenar muscles and sensation to the medial 1.5 fingers 2. **Deep branch** — supplies the interossei, lumbricals (medial two), and adductor pollicis **Mnemonic:** **AFD** = Abductor pollicis brevis, Flexor pollicis brevis, Opponens pollicis (supplied by **median** nerve, not ulnar). ## Why Option 3 Is Wrong The ulnar nerve passes **superficial to** (not through) the flexor retinaculum via Guyon's canal. The median nerve is the one that passes through the carpal tunnel.