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.
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.
As its name suggests,
this muscle adducts the thumb.
So it draws it closer towards the palm
of the hand.
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.
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.
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.
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.
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.
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.
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
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.
So now let’s turn to the carpal tunnel. Very
similar to the arrangement we had on the dorsum