Where is the muscle located and how is it structured?
The muscle lies in the deep layer of the forearm. In this layer, it is located medially, whereas laterally to it lies the flexor pollicis longus (m. flexor pollicis longus).
- Origin (origo) — anterior and medial surfaces of the ulna (ulna), as well as the interosseous membrane (membrana interossea).
- Insertion (insertio) — distal phalanges of digits II–V.
At the level of the proximal phalanges, the tendons of the flexor digitorum profundus pass through the split tendons of the flexor digitorum superficialis (m. flexor digitorum superficialis). At this site, a tendinous chiasm (chiasma tendineum) is formed, after which the tendons of the flexor digitorum profundus continue their path to the distal phalanges.
What is its function?
- Flexion of digits — the muscle flexes the distal phalanges of digits II–V.
- Flexion of the wrist — the muscle participates in wrist flexion.
- Lumbrical muscles (mm. lumbricales I–IV) originate from the lateral sides of the flexor digitorum profundus tendons. They flex the metacarpophalangeal joints and extend the interphalangeal joints, forming the «lumbrical position».
Blood supply and innervation
The muscle has dual innervation:
- Medial, ulnar part — innervated by the ulnar nerve (n. ulnaris); participates in the flexion of the distal phalanges of digits IV and V.
- Lateral, radial part — innervated by the median nerve (n. medianus); participates in the flexion of the distal phalanges of digits II and III.
Blood supply is provided by two arteries:
- Ulnar artery (a. ulnaris).
- Anterior interosseous artery (a. interossea anterior), which lies on the interosseous membrane beneath the flexor pollicis longus and flexor digitorum profundus, and branches out to the deep flexors.
Topography and adjacent structures
The following structures of the forearm, wrist, and hand are associated with the flexor digitorum profundus:
- In the forearm — ulnar artery (a. ulnaris), flexor digitorum superficialis (m. flexor digitorum superficialis), and Pirogov's (Parona) space.
- In the wrist region — tendons of the flexor digitorum profundus (tendines m. flexor digitorum profundus) and flexor retinaculum (retinaculum mm. flexorum).
- In the hand and digits — tendons of the flexor digitorum profundus, common flexor sheath (vagina communis musculorum flexorum), synovial sheath of flexor tendon (vagina synovialis tendinis flexoris), and fibrous sheath of flexor tendon (vagina fibrosa tendinis flexoris). The tendon of the deep flexor extends to the distal phalanx.
Class and exam questions
What is the difference in insertion between the deep and superficial finger flexors?
The tendons of the superficial flexor attach to the middle phalanges, splitting into two slips. The tendons of the deep flexor pass through the split tendons of the superficial flexor and attach to the distal phalanges.
Which nerves innervate the flexor digitorum profundus?
The muscle has dual innervation: the radial part for digits II–III is innervated by the median nerve, and the ulnar part for digits IV–V is innervated by the ulnar nerve.
Where do the lumbrical muscles of the hand originate?
Lumbrical muscles (mm. lumbricales) originate from the lateral sides of the flexor digitorum profundus tendons.
What else to study on this topic
- Flexor digitorum superficialis muscle (m. flexor digitorum superficialis)
- Pirogov-Parona fascial space
- Lumbrical muscles of the hand (mm. lumbricales)
- Synovial sheaths of the hand tendons
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 «Flexor digitorum profundus» 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.