The flexor carpi ulnaris (FCU) is a

muscle Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of muscl ...

of the

forearm The forearm is the region of the upper limb between the elbow and the wrist. The term forearm is used in anatomy to distinguish it from the arm, a word which is most often used to describe the entire appendage of the upper limb, but which in ...

that flexes and

adducts An adduct (from the Latin ''adductus'', "drawn toward" alternatively, a contraction of "addition product") is a product of a direct addition of two or more distinct molecules, resulting in a single reaction product containing all atoms of all co ...

at the wrist joint.

Structure

Origin

The flexor carpi ulnaris has two heads; a humeral head and ulnar head. The humeral head originates from the medial epicondyle of the humerus via the common flexor tendon. The ulnar head originates from the medial margin of the olecranon of the ulnar and the upper two-thirds of the dorsal border of the ulnar by an aponeurosis. Between the two heads passes the ulnar nerve and ulnar artery.

Insertion

The flexor carpi ulnaris inserts onto the

pisiform The pisiform bone ( or ), also spelled pisiforme (from the Latin ''pisifomis'', pea-shaped), is a small knobbly, sesamoid bone that is found in the wrist. It forms the ulnar border of the carpal tunnel. Structure The pisiform is a sesamoid bone, ...

, hook of the hamate (via the

pisohamate ligament The pisohamate ligament is a ligament in the hand. It connects the pisiform to the hook of the hamate. It is a prolongation of the tendon of the flexor carpi ulnaris. It serves as part of the origin for the abductor digiti minimi. It also forms t ...

) and the anterior surface of the base of the

fifth metacarpal The fifth metacarpal bone (metacarpal bone of the little finger or pinky finger) is the most medial and second-shortest of the metacarpal bones. Surfaces It presents on its base one facet on its superior surface, which is concavo-convex and artic ...

(via the

pisometacarpal ligament The pisometacarpal ligament joins the pisiform to the base of the fifth metacarpal bone. It is a continuation of the tendon of the flexor carpi ulnaris The flexor carpi ulnaris (FCU) is a muscle of the forearm that flexes and adducts at the wrist ...

Action

The flexor carpi ulnaris flexes and adducts at the

wrist joint In human anatomy, the wrist is variously defined as (1) the carpus or carpal bones, the complex of eight bones forming the proximal skeletal segment of the hand; "The wrist contains eight bones, roughly aligned in two rows, known as the carpal ...

Innervation

The flexor carpi ulnaris is innervated by the ulnar nerve. The corresponding spinal nerves are C8 and T1.

Tendon

The tendon of flexor carpi ulnaris can be seen on the anterior surface of the distal forearm. On a person's distal forearm, just before the wrist, there are either two or three tendons. The tendon of the flexor carpi ulnaris is the most medial (closest to the little finger) of these. The most lateral one is the tendon of

flexor carpi radialis muscle In anatomy, flexor carpi radialis is a muscle of the human forearm that acts to flex and (radially) abduct the hand. The Latin ''carpus'' means wrist; hence flexor carpi is a flexor of the wrist. Origin and insertion The flexor carpi radialis is ...

, and the middle one, not always present, is the tendon of

palmaris longus The palmaris longus is a muscle Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much long ...

Function

The muscle, like all flexors of the forearm, can be strengthened by exercises that resist its flexion. A

wrist roller The wrist roller is a device designed for strengthening the forearm muscles together in a rolling-pulling motion. It consists of a bar of varying lengths, with a cord or rope attached, which the user rolls and unrolls. This is resisted by the weight ...

can be used and

wrist curls The wrist curl is a weight training exercise for developing just the wrist flexor muscles of the forearm. It is therefore an isolation exercise. Ideally, it should be done in combination with the "reverse wrist curl" (also called wrist extension) ...

with

dumbbell The dumbbell, a type of free weight, is a piece of equipment used in weight training. It can be used individually or in pairs, with one in each hand. History The forerunner of the dumbbell, halteres, were used in ancient Greece as lifting ...

s can also be performed. These exercises are used to prevent injury to the

ulnar collateral ligament of elbow joint The ulnar collateral ligament (UCL) or internal lateral ligament is a thick triangular ligament at the medial aspect of the elbow uniting the distal aspect of the humerus to the proximal aspect of the ulna. Structure It consists of two portio ...

Variability

The muscle can be doubled as accessory flexor carpi ulnaris muscle and is often accompanied by concomitant variants.

Clinical significance

Ulnar entrapment by the aponeurosis of the two heads of the flexor carpi ulnaris muscle may cause

cubital tunnel syndrome Ulnar nerve entrapment is a condition where the ulnar nerve becomes physically trapped or pinched, resulting in pain, numbness, or weakness, primarily affecting the little finger and ring finger of the hand. Entrapment may occur at any point from ...

. Tendon of flexor carpi ulnaris can be used for tendon transfer.

Additional images

Gray214.png, Bones of left forearm. Posterior aspect. Gray219.png, Bones of the left hand. Volar surface showing its insertion into the

bone and then via

ligaments A ligament is the fibrous connective tissue that connects bones to other bones. It is also known as ''articular ligament'', ''articular larua'', ''fibrous ligament'', or ''true ligament''. Other ligaments in the body include the: * Peritoneal li ...

into the

hamate The hamate bone (from Latin hamatus, "hooked"), or unciform bone (from Latin ''uncus'', "hook"), Latin os hamatum and occasionally abbreviated as just hamatum, is a bone in the human wrist readily distinguishable by its wedge shape and a hook-l ...

bone and 5th

metacarpal In human anatomy, the metacarpal bones or metacarpus form the intermediate part of the skeletal hand located between the phalanges of the fingers and the carpal bones of the wrist, which forms the connection to the forearm. The metacarpal bones ar ...

bone, acting to flex and adduct the wrist joint. Gray417_color.PNG, Cross-section through the middle of the forearm. Slide4q.JPG, Flexor carpi ulnaris muscle

References

External links

* {{Authority control Muscles of the upper limb Forearm