Where is the muscle located and how is it structured?
The flexor carpi ulnaris is part of the medial compartment of the forearm, which contains muscles originating from the medial epicondyle of the humerus. In the first (superficial) layer of this group, it occupies the most medial position.
The muscle has two heads:
- Humeral head (caput humerale) — originates from the medial epicondyle (epicondylus medialis).
- Ulnar head (caput ulnare) — originates from the olecranon (olecranon).
In the region of the elbow joint, the muscle forms a tendinous arch. Distally, the tendon of the flexor carpi ulnaris passes beneath the deep fascia of the forearm (fascia propria) on the ulnar side.
Insertion (Insertio): the tendon attaches to the pisiform bone (os pisiforme). Further tendinous bands continue to the hamate bone (hamatum) and the base of the 5th metacarpal bone.
What is its function?
Main functions of the flexor carpi ulnaris:
- Wrist flexion.
- Adduction of the hand — movement of the hand in the ulnar direction.
Blood supply and innervation
- Innervation: n. ulnaris (C7–C8).
- Blood supply: a. ulnaris, superior and inferior ulnar collateral arteries (a. collateralis ulnaris superior et inferior).
Topography and relation to neurovascular bundles
The flexor carpi ulnaris serves as a landmark for locating the structures of the ulnar neurovascular bundle in the forearm:
- In the upper third of the forearm: the ulnar nerve (n. ulnaris) passes between the humeral and ulnar heads of m. flexor carpi ulnaris.
- In the middle and lower thirds: the ulnar artery (a. ulnaris) runs in the groove between the flexor carpi ulnaris and the flexor digitorum superficialis (m. flexor digitorum superficialis). At the border with the middle third, the ulnar nerve joins the artery; thereafter, the nerve lies medially to the artery.
- In the wrist region: the dorsal carpal branch of the ulnar artery (ramus carpalis dorsalis) passes medially beneath the tendon of the flexor carpi ulnaris, then perforates the fascia and emerges onto the dorsum of the hand.
- Guyon's canal (canalis ulnaris): at the lateral margin of the pisiform bone, the deep fascia splits to form a canal containing the ulnar neurovascular bundle.
Adjacent structures on cross-sections
On cross-sections of the forearm among the labeled structures are the ulna (ulna), flexor digitorum profundus (m. flexor digitorum profundus), and the ulnar nerve.
In the superficial layer lateral to the flexor carpi ulnaris, the following structures are located sequentially:
- Palmaris longus (m. palmaris longus).
- Flexor carpi radialis (m. flexor carpi radialis).
- Pronator teres (m. pronator teres).
Note: In the elbow region, separating these muscles of the superficial layer can be difficult; their course is better traced distally in the anterior forearm.
Class and exam questions
Where does the ulnar nerve run in relation to the flexor carpi ulnaris?
In the upper third of the forearm, the ulnar nerve passes between the two heads of this muscle — the humeral and ulnar. At the border with the middle third, it merges with the ulnar artery into a single bundle; further down, it lies medially to the artery.
To which bones does the muscle tendon attach?
The tendon attaches to the pisiform bone (os pisiforme) and also continues to the hamate bone (hamatum) and the base of the 5th metacarpal bone.
Which muscles are in the same layer as the flexor carpi ulnaris?
It is located in the superficial layer of the medial compartment of the forearm. Lateral to it lie the palmaris longus, flexor carpi radialis, and pronator teres.
What else to study on this topic
- Ulnar nerve (n. ulnaris)
- Ulnar artery (a. ulnaris)
- Guyon's canal (canalis ulnaris)
- Flexor digitorum superficialis
Study the complete topic in the Anatomy course
This is a summary. The course covers everything tested in classes and exams.
- Complete study guide on the "Flexor carpi ulnaris" topic and 1,363 other subject pages
- Assignments and quizzes after every topic — just like in a colloquium
- AI tutor answers questions on the topic anytime
- 295 video lessons by subject
Other topics in the "Anatomical Structures" section
Free video lessons: AnatomyShort lessons with study notes — no registration required.
Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.