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Origins, insertions, innervation and functions of the suboccipital muscles.
Hello, everyone. This is Joao from Kenhub, and welcome to another anatomy tutorial where, this time, we’re going to be talking about a group of four muscles that are known as the suboccipital muscles, which you can see now on the image.
We’re looking at a posterior view of the neck and also your head of course, you see here. And this is where the suboccipital muscles are located, just below this bone here, which is known as the occipital bone. Hence the name, suboccipital muscle.
So in anatomy, we try to keep things very simple.
And without keeping you waiting, let’s first list these four muscles before we talk about their origins, insertion, and also innervation, and functions associated to these suboccipital muscles. There are two. They are the rectus capitis posterior minor and then the major one, so the rectus capitis posterior major.
There are other two which have similar names. The obliquus capitis inferior and then the superior one.
Before we talk about these muscles, I want to make a clear point here that this is the easiest part of the tutorial, which is to know that the innervation of these four muscles will be provided by these nerves that you see here highlighted in green on this image. These are known as the…
They’re posterior branches of the first spinal nerve, which you also see here on this image. And keep in mind that we’re looking at a posterior view of the suboccipital region. These nerves are, then, the suboccipital nerves.
And let’s start with the very first one on the list, these two that you see here. This is the rectus capitis posterior minor. This one arises by a narrow, pointed tendon from the tubercle on the posterior arch of this bone here, the atlas (the first cervical vertebra).
And then it goes all the way to insert on the medial part of the inferior nuchal line of the occipital bone that I talked about and the surface between it and the foramen magnum. It also takes some attachment to the spinal dura mater.
Now, a quick word on the different actions or functions associated to the rectus capitis posterior minor. Now, this muscle will be able to, then, perform a minor degree of extension of the head at the neck.
We’re now ready to move on to the next one that you see here highlighted in green. This one is the rectus capitis posterior major, and you have one on each side. So two muscles as you can see here.
This muscle will be, then, arising by a pointed tendon as well from the spinous process of the axis. This time, the second cervical vertebra.
It then goes all the way to insert on the lateral part of the inferior nuchal line, as you can see here, of the occipital bone and the surface of the bone immediately below the line.
When it comes to the different functions or actions associated to the rectus capitis posterior major, you see here the muscle contracted on this image and a little bit on the movement that it’s causing to say that its main actions are associated to extension and also rotation at the atlanto-occipital joint (this joint here formed between the occipital bone and the first cervical vertebra or the atlas).
We’re ready to move on to the next muscles that you see here highlighted in green. This is one is the obliquus capitis inferior. There are two as well, as you can see here highlighted in green.
The obliquus capitis inferior muscle is the larger of the two oblique muscles of the neck, and it arises from the spinous or the apex of the spinous process of the axis, as you can see here on this image.
Then it goes all the way to insert, as you can also see here on the image, on the transverse processes of the atlas. So now, this time, on the first cervical vertebra.
Now, the obliquus capitis inferior is responsible for rotation of the head and first cervical vertebra but this time at the atlanto-axial joint. So the joint between the first cervical vertebra (or the atlas) and the axis (the second cervical vertebra).
And you notice here on this image how the head is turned to the side to show a bit of the rotation of the head, which is one of the functions of… or the main function of the obliquus capitis inferior.
We’re ready now to move on to the last set of muscles that we were supposed to talk about, and this one is the obliquus capitis superior. This muscle will be arising from the transverse process of the atlas or the transverse processes of the first cervical vertebra as you can see here, then goes all the way to insert into the lateral half of the inferior nuchal line, as you can see on the external surface of the occipital bone.
Now, the obliquus capitis superior muscle will be acting at the atlanto-occipital joint to extend the head and also flex the head to the ipsilateral side. In other words, it’s going to be flexing…
You have two muscles of course, one on each side. We’re just showing you one, but when this muscle is contracting, then it provides flexion of the head to the lateral or to the same side.
“Ipsilateral” meaning to the same side where the contraction is happening.