Human Anatomy - Kotsan I. Y. 2009

Muscles and Fascia of the Upper Limb
Anterior Muscle Group of the Forearm
Third Layer of Muscles of the Anterior Forearm Group

The deep flexor Muscle of the fingers (m. flexor digitorum profundus) originates from the upper two-thirds of the palmar surface of the ulna and partially from the interosseous membrane. Similar to the superficial digital flexor, it features a muscle belly from which four tendons extend through the carpal tunnel toward the digits. These tendons pass between the split slips of the superficial flexor tendons and insert into the bases of the distal Phalanges of digits 2–5. Function: flexes all JOINTS OF THE hand, including the distal phalanges of the fingers. However, isolated flexion of the distal phalanges is possible only in certain individuals and is typically achieved when the middle phalanges are fixed.

Innervation: median and ulnar nerves (CV–ThI).

The long flexor muscle of the thumb (m. flexor pollicis longus) has a fusiform shape. It originates from the anterior surface of the radius and the interosseous membrane of the forearm. The tendon of this muscle passes through the carpal tunnel within a separate synovial sheath and inserts into the Base of the distal phalanx of the thumb. Function: flexes the distal phalanx of the thumb, as well as all joints of the hand it crosses.

Innervation: median nerve (CV–ThI).



Last update: 08/08/2026

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