What is the action of the palmaris longus muscle?

The palmaris longus muscle primarily flexes the wrist. It is a small, superficial muscle in the anterior forearm that assists in wrist flexion and provides some weak assistance in thumb abduction. When contracted, it creates a visible tendon in the middle of the wrist that can be seen when touching the thumb and little finger together while flexing the wrist. The muscle originates from the medial epicondyle of the humerus and inserts into the palmar aponeurosis, a fibrous sheet in the palm of the hand. Despite its action, the palmaris longus is considered functionally insignificant, as its absence (which occurs in about 10-15% of the population) does not result in any noticeable decrease in grip strength or hand function. This is why the tendon is commonly harvested for reconstructive surgeries without significant functional consequences. The muscle is innervated by the median nerve and receives blood supply from the ulnar recurrent artery.