Overview
This lecture reviews the main nerves of the hand (median, ulnar, radial), their branches, functions, and the implications of injury, with an emphasis on sensory and motor deficits.
Nerves Supplying the Hand
- Three main nerves supply the hand: median, ulnar, and radial nerves.
- These nerves originate from the brachial plexus and provide both motor and sensory functions.
Median Nerve in the Hand
- Passes through the carpal tunnel, making it prone to compression injuries.
- Before entering, gives off the palmar cutaneous branch (sensory to mid-palm, superficial to carpal tunnel).
- Once in the hand, branches into lateral, medial, and recurrent branches.
- Recurrent branch innervates thenar muscles (intrinsic thumb muscles).
- Lateral branch: sensory to palmar thumb and lateral index finger, motor to 1st lumbrical.
- Medial branch: sensory to palmar surfaces of index, middle, and part of ring finger, motor to 2nd lumbrical.
- Common palmar digital nerves divide into proper palmar digital nerves along the fingers.
Ulnar Nerve in the Hand
- Runs superficial to the flexor retinaculum, not through carpal tunnel.
- Gives off superficial palmar branch (sensory to medial palm) and dorsal branch (sensory to dorsal little and half ring finger).
- Superficial branch: mostly sensory to palmar little and half ring finger, and fingertip surfaces.
- Deep branch: motor to hypothenar muscles, lumbricals (4th and 5th digits), all interossei, adductor pollicis, and part of flexor pollicis brevis.
- Palmaris brevis muscle is innervated by the superficial branch.
Radial Nerve in the Hand
- Superficial branch runs dorsally, is mostly sensory.
- Supplies sensory innervation to dorsal thumb, first and second finger, and lateral half of third finger (excluding tips).
Cutaneous Innervation & Dermatomes
- Median, ulnar, and radial nerves together cover all sensory innervation of the hand.
- Dermatomal testing: C6 (thumb), C7 (index & middle), C8 (ring & little finger).
Nerve Injury and Repair
- Nerves can be crushed, stretched, compressed, or severed.
- A severed nerve may form a neuroma (painful, non-functional).
- Surgical reconnection of nerves can restore function if done skillfully.
Key Terms & Definitions
- Carpal tunnel — Passage in the wrist where the median nerve enters the hand.
- Thenar eminence — Muscle group at the base of the thumb.
- Hypothenar eminence — Muscle group at the base of the little finger.
- Lumbricals — Small intrinsic hand muscles involved in finger movement.
- Dermatome — Area of skin supplied by sensory fibers from a single spinal nerve root.
- Neuroma — Painful nerve tissue growth after nerve injury.
Action Items / Next Steps
- Review diagrams of hand nerve innervation for visual understanding.
- Read about the function and clinical relevance of lumbrical and interosseous muscles.
- Practice identifying nerve supply to different parts of the hand for exams.