Palmaris longus muscle
Musculus palmaris longus
Palmaris longus is a slim, often absent forearm muscle whose long tendon runs to the palm and tightens the palmar aponeurosis.
At a glance
- English
- Palmaris longus muscle
- Latin (TA2)
- Musculus palmaris longus
- System
- Muscle
- Region
- Upper limb
- Side
- Paired, left and right
About the palmaris longus muscle
Palmaris longus is a small superficial flexor on the front of the forearm, lying between flexor carpi radialis on its lateral side and flexor carpi ulnaris on its medial side. It has a short belly and a very long, thin tendon, and it is the most variable muscle of the forearm. It is missing on one or both sides in many people, with no loss of grip.
The muscle starts from the common flexor tendon on the humeral medial epicondyle and from the septa beside it. Its spindle-shaped belly soon gives way to a slender tendon in the upper half of the forearm. At the wrist the tendon passes in front of the flexor retinaculum, not through the carpal tunnel, and spreads out into the palmar aponeurosis, the tough sheet of fascia beneath the skin of the palm. Some fibres attach to the retinaculum itself and sometimes send a slip to the thenar muscles.
It tightens the palmar aponeurosis, helping to cup the palm and to resist shearing forces on the skin when gripping. It is also a weak flexor of the wrist. The median nerve supplies it, and its blood comes from muscular branches of the ulnar artery.
To see whether the tendon is present, the patient pinches the thumb and little fingertips together and bends the wrist; if present, the tendon then stands out in the middle of the wrist. Because it can be taken without loss of function, it is a favourite graft for rebuilding tendons and ligaments elsewhere, including the elbow. The median nerve runs just under and slightly lateral to it at the wrist, so the tendon is a guide for injections into the carpal tunnel.
Attachments, action and supply
- Origin
- Humeral medial epicondyle by the common flexor tendon, and the adjoining septa.
- Insertion
- Palmar aponeurosis and the front of the flexor retinaculum.
- Action
- Tenses the palmar aponeurosis; weakly flexes the wrist.
- Nerve supply
- Median nerve (C7, C8).
- Blood supply
- Muscular branches of the ulnar artery.
Anthromica
See the palmaris longus muscle where it really sits, with every layer of the body around it.
- Every layer, one body. Peel from muscle to bone, nerve, vessel and organ, and turn it any way.
- English and Latin. Every structure named the way your exam names it.
- Quiz until it sticks. Short drills on the structures you keep missing.
Free to start. No card.
