Palmaris brevis muscle

The palmaris brevis is a small, thin, quadrilateral muscle found superficially on the ulnar (little finger) side of the palm, covering the hypothenar eminence.

Origin and insertion

It originates by tendinous fasciculi from the flexor retinaculum and palmar aponeurosis. From there, its muscle fibers insert directly into the skin on the ulnar border of the palm.

Innervation

The palmaris brevis receives its innervation from the superficial branch of the ulnar nerve. This sets it apart from most other intrinsic hand muscles, which typically get their nerve supply from the deep branch of the ulnar nerve or the median nerve.

Action

Functionally, the palmaris brevis helps deepen the hollow of the palm. It also acts as a muscular barrier, protecting the neurovascular structures of the ulnar canal during gripping and compressive activities. Additionally, it's thought to stabilize the skin and hypothenar fat pad, aiding in grip stability and shielding the underlying ulnar nerve and artery from potential trauma.