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So, if we reflect the semispinalis capitis, we'll find the suboccipital triangle. The,
subocciptial triangle is bounded inferiorly by the inferior oblique muscle, "this is the
inferior oblique muscle" and superiorly, here is the superior oblique muscle. The two oblique
muscles are the lateral boundaries of the triangle and they meet at the transverse process
(at the tip of the transverse process of the 1st cervical vertebra of the atlas). So, this
is the superior oblique muscle "all this is the superior oblique muscle" and this is the
inferior oblique, which terminates at the tip of the transverse process of the 1st cervical
vertebra of the atlas. And, the superior oblique arises from the transverse process of the
atlas. So, they meet at this "pin", (this pin represents the tip of the transverse process
of the atlas). The medial boundary of the triangle are the two recti muscles, which
have an oblique course. Although, they are called "recti", yet they have an oblique course,
"this is the *** capitis posterior major muscle" and medial to it we have the ***
capitis posterior minor. Therefore, if we remove the semispinalis capitis, we'll find
the suboccipital triangle. The, suboccipital triangle has three boundaries, superior lateral
boundary which is the superior oblique, inferior lateral boundary which is the inferior oblique
and medial boundary formed of the recti muscles: the *** capitis posterior major muscle
and the *** capitis posterior minor muscle. In this triangle, we'll have the suboccipital
nerve, which is the dorsal ramus of the 1st cervical nerve, and it is the nerve that supplies
all the muscles that bound the triangle. So, this is the suboccipital nerve, which is the
dorsal ramus of "C1 and it supplies the superior oblique, the inferior oblique, the ***
capitis posterior major muscle and the *** capitis posterior minor muscle. Below the
inferior oblique, there is the greater occipital nerve, which is the dorsal ramus of the 2nd
cervical nerve. The greater occipital nerve has nothing to do with the supply of the muscles
of the suboccipital triangle, but it helps in the supply of the root of the semispinalis
capitis. Therefore, if I remove the semispinalis capitis, I'll have the suboccipital triangle,
which is bounded superiorly and laterally by the superior oblique muscle. The inferior
boundary is the inferior oblique muscle. And, below the inferior oblique muscle, there is
the greater occipital nerve. Above, the inferior oblique muscle (inside the triangle), there
is the suboccipital nerve. And, the medial boundary of the triangle is formed of the
*** capitis posterior major muscle and the *** capitis posterior minor muscle.
Inside the triangle and deep, there is the third part of the vertebral artery . This
is the vertebral artery but, it's opened. So, the two main contents of the triangle,
we have the the third part of the vertebral artery, which is opened here. We have the
suboccipital nerve that supplies the muscles of the triangle and below the triangle we
have the greater occipital nerve. Also, there is a plexus of veins here (which is removed),
and it is a very important plexus of veins, this is the suboccipital plexus. So, the three
main contents are the suboccipital plexus, we have the third part of the vertebral artery
which is opened here, this is the suboccipital nerve which is the dorsal ramus of "C1" and
supplies the muscles of the triangle and this is the greater occipital nerve. This finishes
the boundaries and the contents of the suboccipital triangle