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fifth digit. Now let’s turn to the fourth layer.
This is the interosseous layer between the
metatarsals. Again, similar to the hand, we
have a whole series of dorsal and plantar
interossei muscles. We have three plantar
interossei and we have four dorsal interossei.
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We can see the dorsal interossei are coming
from adjacent metatarsals. So we can see we’ve
got the first dorsal interossei here, second,
third, and fourth. And these are coming from
the two adjacent metatarsal bones, whereas
here, the plantar interossei, we can see these
are only coming from the third, fourth, and fifth
metatarsals, only coming from one of them.
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So we have our bipennate and unipennate
musculature. So if we look at the origins
and insertions of this interossei muscle,
then the plantar interossei originate from
the medial surface of the third or fifth metatarsals.
And they insert on the medial surface of the
proximal phalanx of digits 3 to 5. The dorsal
interossei run from adjacent surfaces of the
first to fifth metatarsals, and their insertions
are quite different. The first dorsal interossei
attaches to the medial surface of the proximal
phalanx of digit two, whereas, the second,
third and fourth dorsal interossei attach to
the lateral surface of the proximal phalanx
of digits 2 to 4. So there’s a difference
there for the first, the second, third, and
fourth dorsal interossei. All of the interossei
are supplied by the plantar nerve. So the
plantar interossei are involved in adducting
digits 3 to 5. Remember, we can use PAD for
the plantar interossei adduct the digits.
And they’re also important in flexing the
metatarsophalangeal joints. The dorsal interossei,
these are involved in abducting. So we have
DAB, dorsal interossei abduct digits 2 to
4, and these were also involved in flexing
the metatarsophalangeal joints. So if we were
to remove the plantar aponeurosis and we were