Flexor Digitorum Superficialis
Humeroulnar head: Common flexor tendon; anterior part of ulnar collateral ligament; adjacent intermuscular septa and medial aspect of the coronoid process.
Radial head: A fibrous arch continues to the radial tuberosity and anterior oblique line to which the muscle is attached as a thin sheet.
Flexor digitorum superficialis arises from its proximal attachments, courses distally, and forms, within its substance, an intermediate tendon from which distal fibers of the muscle arise. These are the fibers of the deeper part of the muscle which give rise to deep tendons for the index and little fingers. The fibers for the middle finger arise mostly from the radius with a small contribution from the common flexor origin. The fibers from the ring finger arise from the common flexor origin. The muscle fibers, and therefore the tendons, of the middle and ring fingers lie superficial to the index and little.
These tendons pass in this relationship within a common synovial flexor sheath beneath the flexor retinaculum, and then diverge towards the individual digital rays.
At the base of the respective proximal phalanx each superficialis tendon divides into two slips (bifurcation) which pass around the tendon of the flexor digitorum profundus. The tendon slips cross over dorsal to the profundus tendon, at the chiasm of Camper thus forming a fibrous tunnel before inserting into the palmar aspects of the shafts of the middle phalanges within the A4 annular flexor tendon pulley.
The tendon blood supply within the digital fibrous sheaths is by vincula; the vinculum longum superficialis and vinculum brevis.
Median nerve (C 7, 8and T1).
Flexion of all of the joints crossed; primarily the proximal interphalangeal (PIP), and secondarily the metacarpophalangeal (MCP) and the wrist joint