Regarding the course and anatomical relationships of the ulnar nerve in the upper limb, all of the following statements are correct EXCEPT:
A. At the wrist, the ulnar nerve divides into superficial and deep branches just distal to the pisiform bone
B. The ulnar nerve arises from the medial cord of the brachial plexus (C8–T1 roots)
C. The ulnar nerve enters the hand by passing superficial to the flexor retinaculum through the carpal tunnel alongside the median nerve
D. In the forearm, the ulnar nerve lies medial to the ulnar artery and runs between the flexor carpi ulnaris and flexor digitorum superficialis
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-YieldNEET PG
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:
Table
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-YieldNEET PG
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.
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