The
flexor digitorum profundus
is a muscle due to which the four fingers (index, middle, ring, and
little) are able to bend. It is located in the anterior compartment
of the forearm. The meaning of this muscle is “deep bender of the
fingers” and it is a Latin name.

There
are two distinct heads of this muscle; both of them originating in
the forearm. As its muscle belly is located in the forearm and it
acts on the fingers, it is considered an extrinsic hand muscle.

There
is a deep layer of ventral forearm muscles formed by flexor
digitorum profundus, flexor pollicis
longus, and pronator quadratus. Also you can lookout more at
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Now,
let us have an overview of the structure of this muscle.

Structure:

This
muscle originates from four sites:

1. The
   medial surfaces of ulna
   
2. The
   adjacent part of theinterosseous
   membrane
   
3. The
   coronoid process of ulna
   
   
4. The
   aponeurosis of the flexor carpi ulnaris muscle
   

The
origin is quite broad and then the muscle takes a slightly narrow
passage towards the hand and ends in fingers.

The
median nerve in the forearm crosses the lateral part of the anterior
surface of this muscle. There are four tendons coming out of this
muscle, one to each of the fingers. These four long tendons run down
the arm through the carpal tunnel and then to the fingers.

Carpal
tunnel is a narrow passage in the wrist of the hand from where the
median nerve passes. If there is a pressure generated on the median
nerve then it results in shakiness, pain, and clumsy feeling in the
hand which is called carpal tunnel syndrome.

This
muscle lies deep to the Flexor
digitorum superficialis so the
tendons of these muscles go through the tendons of superficialis. The
tendons end up attaching to the distal phalanx. That’s why it is
also called the perforating muscle. Lumbricals, which are the
intrinsic muscles of the hand flex the joints of the fingers and they
arise from the radial side of the tendons.

The
main function of this muscle is the flexion of the fingers at the
metacarpophalangeal and interphalangeal joints. It is also associated
with the flexion of the wrist. Muscle fibers are arranged in a way
such that the lateral part inserts to digits 2 and 3 and the medial
part of the muscle inserts into digits 4 and 5.

Innervation:

This
muscle has a dual innervation.

1. The
   medial part of the muscle is innervated by the ulnar nerve and it
   inserts into the fourth and fifth digits.
   
2. The
   lateral part is innervated by the median nerve and it inserts into
   the second and third digits.
   
   

How
does blood supply take place inside the muscle?

At
the origin of the muscle, the blood is supplied with the inferior
ulnar collateral and ulnar recurrent arteries. The ulnar artery
provides blood to the superior part of the muscle belly. Branches of
the ulnar, median arteries, and anterior interosseous provide blood
to the rest of the part of the muscle.

What
is the function of this muscle?

As
we already told you that with this muscle, flexion of the fingers
takes place. Flexion of the digits 2-4 takes place at the
metacarpophalangeal and interphalangeal joints as the muscle pulls
the distal phalanges towards the hand. It acts in synergy with flexor
digiti minimi brevis muscles, flexor
digitorum superficialis, and
lumbricals.

Also,
it is the wrist flexor. It helps the flexor carpi radialis, palmaris
longus, flexor carpi ulnaris, flexor digitorum superficialis, and
flexor pollicis longus muscles to bend the hand at the wrist joint.

A
strong grip of the hand is established and maintained with flexor
digitorum profundus.

Let's
have a quick look at the summarization.

Origination:
Originates in the anterior surface of ulna, interosseous membrane

Insertion:
It inserts into palmar surfaces of distal phalanges of the four
fingers.

Action:
Finger and Wrist flexion

Innervation:
Median nerve and Ulnar nerve

That’s
it, here was all the information you need to know about flexor
digitorum profundus.