Flexor Digitorum Superficialis: Origin, Action & Insertion

Instructor: Artem Cheprasov

Artem has a doctor of veterinary medicine degree.

The flexor digitorum superficialis is a muscle that helps to flex your fingers. But which fingers? Find out in this lesson as you go over the origin, insertion, and actions of the flexor digitorum superficialis.

Flexor Digitorum Superficialis

Take your hand and straighten your fingers. Now bend (flex) every finger except for the thumb. To help accomplish this flexion, you used a certain muscle known as flexor digitorum superficialis. This muscle has numerous actions, proximal, and distal attachment points. Let's learn about them in this lesson.

Origin & Insertion

Origin

When we refer to the proximal attachment points of this muscle, we're talking about its origin. In other words, where does this muscle begin? This muscle has two ''heads,'' or two parts by which it arises. These two parts are known as the humero-ulnar head and the radial head. It'll make sense in a second as to why that's the case.

The humero-ulnar head derives its name from the fact that it arises in part from the humerus, which is the upper arm bone, and from the ulna. The ulna is one of two bones that make up your forearm. The ulna gives you your ''pointy'' elbow, which is technically called the olecranon.

Flexor Digitorum Superficialis.
Flexor Digitorum Superficialis

This head specifically originates from the following points:

  • Medial epicondyle of the humerus. Can you feel your elbow point? Can you then feel two bony knobs on either side of your elbow point? The one closer to the body is the medial epicondyle of the humerus.
  • Ulnar collateral ligament, which is a ligament that helps stabilize your elbow, especially when throwing something like a baseball.
  • Coronoid process of the ulna. This is a bony projection on the ulna that helps form a notch where the humerus inserts onto the ulna to help compose the elbow joint.

The radial head of flexor digitorum superficialis gets its name from the radius, the other bone of the forearm. The radial head originates from the anterior portion of the radius. In other words, it arises from the front-facing (anterior) portion of the radius.

Insertion

Got all that straight so far? Then let's get to this muscle's distal attachment point: in other words, its insertion point. Or, even more simply, where this muscle ends.

Flexor digitorum superficialis inserts onto the bodies of the middle phalanges of the medial four digits. Wow! Not much easier than the multiple origins, is it? Let's break this down again.

The medial four digits are all of your fingers, minus the thumb. The middle phalanges are the middle bones of each finger. For instance, take a look and feel about your index finger. You should feel three distinct bones that make up this finger. The one in the middle is, logically, the middle phalanx. This phalanx has nothing to do with heroic Spartans. A phalanx, in anatomy, is a bone of a finger or toe, that's all. Your finger is comprised of a distal phalanx (the fingertip), middle phalanx, and proximal phalanx (the finger bone closest to your palm).

Action

So with all that tough stuff out of the way, let's get to the more relatable things. What does this muscle actually do? Well, the introduction gave part of it away.

Its primary actions are as follows:

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