Adductor Compartment – Anatomy of the Hand

by James Pickering, PhD

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    00:00 So now let’s move to the adductor compartments. The adductor compartment only contains one muscle. And this is important in adducting the thumb as the name suggests. But there are two heads to the adductor pollicis muscle. There is an oblique head and there is a transverse head. And here on the diagram, we can see we have this adductor pollicis muscle here, this triangular-shaped muscle. It actually runs underneath here, the tendons of flexor digitorum profundus and the lumbricals which we’ll come back to. It’s running deep to those, but it’s passing out from the central region of the palm. It’s passing out towards the thumb, and it has got two heads. The more transversely orientated part of the muscle is the transverse head. The more obliquely orientated part is the oblique head. And these two heads converge onto a common insertion point. So the adductor pollicis, its oblique head comes from the base of the second and third metacarpals, and also the capitate bone.

    01:07 The transverse head comes from the anterior surface of the third metacarpal. So we can see the origin of the two heads. A common insertion onto the medial side of the proximal phalanx of the thumb, and this is supplied via the deep branch of the ulnar nerve.

    01:23 As its name suggests, this muscle adducts the thumb.

    01:30 So it draws it closer towards the palm of the hand.

    01:34 Now let’s move on to the hypothenar eminence. The hypothenar eminence is located on the medial aspect of the hand. We can see we’ve got a collection of muscles here. Like the thenar eminence, there are going to be three muscles within the hypothenar eminence, three muscles: abductor digiti minimi, flexor digiti minimi brevis, and opponens digiti minimi.

    02:05 Now, if we have a look, we can see that these muscles form a similar arrangement to that of the thenar eminence, in that some are deeper to others.

    02:15 So, let’s have a look. First of all, we can see abductor digiti minimi here, and we can see where we’ve cut it off is the most superficial muscle, but we can see its two parts there. And then deep to this muscle, deep to abductor digiti minimi, we find we have flexor digiti minimi. Sometimes this can be called brevis like I’ve included in the text here. But as we don’t have a longus version of it, it’s not necessary and it can just be flexor digiti minimi. And then next to it, we have opponens digiti minimi.

    02:49 So these are the three muscles that lie within the hypothenar eminence. Abductor digiti minimi, you can see it has been cut here, passing along the most medial aspect. Deep to it, we have flexor digiti minimi, and then slightly lateral to that, we have opponens digiti minimi.

    03:10 Within the subcutaneous tissue over the hypothenar eminence, there is a small muscle, a small muscle over the hypothenar eminence, and this is known as palmaris brevis. We can’t really see it here. But palmaris brevis is an important muscle, and it helps along with palmaris longus to tighten the palmar fascia, and this helps supporting of the grip.

    03:37 So if we have a look at the origins and the insertions for these muscles, well here, we have the muscles, abductor digiti minimi. This is originating from the pisiform, bone, and it inserts onto the medial side of the proximal phalanx of the fifth digit. So we’re just concentrating on the fifth digit now. This muscle is supplied by the ulnar nerve.

    03:59 So it’s no longer the median nerve. We’ve moved over to the medial side of the hand, and we’re now supplied by the ulnar nerve. Specifically, it’s the deep branch of the ulnar nerve. As the name of the muscle suggests, the function of abductor digiti minimi is to abduct the fifth digit. Flexor digiti minimi, or adding brevis if you want to, originates from the hook of the hamate, and also the flexor retinaculum. It shares an origin with the opponens digiti minimi muscle. So these two muscles share a common origin. However, they have a different insertion. Flexor digiti minimi brevis inserts again onto the medial side of the proximal phalanx of the fifth digit, whereas, opponens digiti minimi inserts onto the medial border of the fifth metacarpal. But all of these muscles have the same nerve supply which is the deep branch of the ulnar nerve.

    05:01 Again, the function of these muscles is indicated by their name. So flexor digiti minimi flexes the proximal phalanx of the fifth digit. And opponens digiti minimi rotates and draws anteriorly the fifth metacarpal. It helps to oppose the little finger and it helps to draw the little finger towards the thumb. So these two digits can touch one another.

    05:29 So now let’s turn to the carpal tunnel. Very similar to the arrangement we had on the dorsum

    About the Lecture

    The lecture Adductor Compartment – Anatomy of the Hand by James Pickering, PhD is from the course Upper Limb Anatomy.

    Included Quiz Questions

    1. Medial side of the proximal phalanx of the thumb
    2. Distal phalanx of the second digit
    3. Lateral side of the distal phalanx of the thumb
    4. Lateral side of the proximal phalanx of the thumb
    5. Medial side of the distal phalanx of thumb
    1. Palmaris brevis
    2. Abductor digiti minimi
    3. Flexor digiti minimi
    4. Opponens digiti minimi
    5. Flexor digitorum profundus
    1. Abductor digiti minimi
    2. Flexor digiti minimi
    3. Opponens digiti minimi
    4. Abductor pollicis brevis
    5. Flexor pollicis brevis

    Author of lecture Adductor Compartment – Anatomy of the Hand

     James Pickering, PhD

    James Pickering, PhD

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