Palmaris brevis muscle

Origin and insertion

The thin palmaris brevis muscle sits entirely within the palmar aspect of the hand, in the subcutaneous tissue of its ulnar side. It originates from the flexor retinaculum and the medial margin of the palmar aponeurosis. Its fibers take a short medial course, after which they insert into the dermis of skin of the hypothenar eminence.

Relations

Lying directly beneath the skin, palmaris brevis is the most superficial muscle on the ulnar side of the hand. Deep to the muscle are the ulnar artery, superficial palmar arch, superficial branch of the ulnar nerve and the muscles of the hypothenar eminence (abductor digiti minimi, flexor digiti minimi brevis and opponens digiti minimi).

Palmaris brevis forms the roof of Guyon’s canal, the fibro-osseous canal found on the ulnar side of the palm through which the ulnar artery and nerve travel into the palmar hand.

Innervation

Palmaris brevis is innervated by the superficial branch of ulnar nerve (C8, T1). This nerve emerges from the medial cord of the brachial plexus.

Blood supply

Blood supply to the palmaris brevis muscle comes from the superficial palmar arch, which is an arterial network formed mainly by the ulnar artery. Some individuals may also receive contributions from the superficial palmar branch of the radial artery or princeps pollicis artery.

Function

The palmaris brevis muscle tightens the palmar aponeurosis while contracting, which wrinkles the hypothenar skin and deepens the palmar fossa while holding a grip. This action helps to position and stabilize the palm during a spherical power grip, where it is necessary to pose the hand in a cup-formation, or during repetitive grip movements.