Middle Layer of the Anterior Compartment of the Forearm

00:01 Now, let's move onto the middle layer and really, we're just looking at flexor digitorum superficialis which we can see here.

00:08 So, flexor digitorum superificialis has really got a couple of heads.

00:12 One that's coming from the humerus, the humero-ulnar head we can see here.

00:17 And one that's coming from the radial side of the forearm which we can see here.

00:22 So, a humero-ulnar head on the medial aspect and we've got a radial head on the more lateral aspect.

00:29 And this muscle is important as it passes all the way through a region known as the carpal tunnel to go and insert onto the digits of the hand, but not the thumb.

00:38 So, it originates from the medial epicondyle, we can see here as part of the humeral aspect of its humeral head.

00:44 And also, the coronoid process of the ulnar part of its humero-ulnar head.

00:50 It then comes from the shaft of the radius which we can see here, forming the radial head.

00:56 And it passes all the way through the carpal tunnel to go and attach to the middle phalanges of the medial four digits.

01:02 So, not the thumb, not the first digit. Importantly, attaches to the middle phalanges of the medial four digits.

01:10 It's innervated via the median nerve which we can see here.

01:14 So, the median nerve supplying flexor digitorum superificalis.

01:18 And the function of the muscle again is very much to flex the wrist so it helps to flex the hand at the wrist joint as it's passing across that joint.

01:27 And it also helps flexion of the proximal interphalangeal joint.

01:31 Remember, the phalanges has three parts to them, a proximal, middle, and distal.

01:37 As this attaches to the middle, it crosses that proximal interphalangeal joint.

01:42 So, it helps to flex some of the digits at that proximal interphalangeal joint.