Intermediate and Deep Muscles of the Back

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Okay so this tutorial is on the deep and intermediate muscles of the back, it kind of follows on from the tutorials on the superficial muscles the extrinsic muscles of the back, so hopefully you should have watched that before going onto watching this one.

But the intermediate muscles of the back are those muscles which attach to the ribs and are involved in respiratory function and the deep muscles of the back are also known as the intrinsic muscles, because they have their embryological development in the back, and these muscles are innervated by posterior rami of spinal nerves, and they are involved in moving the spine and head.

 

Intermediate Muscles

I'll just talk first about the intermediate muscles, so just removing the extrinsic muscles here, which you should all know by now. Okay, so got rid of those - those were the extrinsic muscles that I just got rid of.

 

Here we have the intermediate muscles, and there are only two muscles that you need to know, and they are the serratus posterior superior and the serratus posterior inferior. Just take a look at those, that's that one, and we've got one, the serratus posterior inferior.

 

Those are the intermediate muscles of the back, and as you can see, they're attached to the ribs here and they originate from the spinous processes, so they elevate and depress the ribs. The superior serratus posterior elevates the ribs and the serratus posterior inferior depresses the ribs, which is quite logical. Okay, so next we have the deep muscles of the back, so we've gone from the extrinsic muscles down to the intermediate muscles, and now we're moving onto the deep muscles of the back.

 

I'll just get rid of these intermediate back muscles and underneath we have the intrinsic muscles.

 

Intrinsic Muscles

Like I said before, these muscles are innervate by the posterior rami of spinal nerves, and these muscles extend from the pelvis, right up to the skull, and they have their development, they develop in the back.

 

These muscles are involved in moving the vertebral column, and in moving the head and neck. The muscles which are involved in moving the head and neck are called the spinotransversales muscles, and you've got two spinotransversales muscles - the splenius capitis, and the splenius cervicis, which for some reason is not shown on this model. But the splenius capitis here is this big muscle, so I'll just click that so you can have a look at it a bit more clearly.

 

The splenius capitis originates here and inserts onto the skull.

 

Again, trying to just imagine what function this has. If I just tilt it here, you can see that if this muscle contracts, the skull is drawn backwards, so the neck is extended, and that's if they're both acting together.

 

If they're both acting together, the neck is extended and the head is drawn backwards. If one muscle, if the splenius individually contracts, you can see that the head will be rotate round to one side.

 

Together the splenius capitis will draw the head back and will extend the neck, and if it contracts individually it will just rotate the head round to one side.

 

The two spinotransversales muscles are the splenius capitis, which is these two muscles here, and the splenius cervicis which isn't shown on this model for some reason, but it originates just below the splenius capitis and inserts onto the transverse process of the, of vertebra C1.

 

Erector Spinae

Okay, so those two muscles move the head and neck and next I'm going to talk about the erector spinae muscles.

 

You've got these muscles which move the vertebral column, and you've got the erector spinae and the transversospinales muscles, so first I'll talk about the erector spinae, because they're more superficial, and then I'll move onto the transversospinales muscles which lie underneath the erector spinae...spinae, however you pronounce it.

 

The erector spinae muscles are the largest group of muscles, intrinsic muscles in the back, and they are primary extensors of the vertebral column and head. I'll just highlight these muscles here so we can see them a bit more clearly. These are the erector spinae, just zoom it in to view a bit better.

 

You’ve got three groups of muscles here, you've got the iliocostalis, which is most lateral, the longissimus, and then you've got the spinalis, which is most medial.

 

You’ve got those three muscles: the iliocostalis, the longissimus, and the spinalis. And they all have, they attach at all these different regions of the vertebral column.One way of remembering the erector spinae muscles, you've got the mnemonic - "I long for spinach", so "iliocostalis" lateral, "longissimus" in between the two, and "spinalis" most medial. I long for spinach. Or you could remember the way I try and remember things, so costalis, sort of ribs - they're most lateral, spinalis lies right on the spine, so more medial and then longissimus lies between the two.

 

Those are the erector spinae muscles and they move the vertebral column, extend the vertebral column.

 

Transversospinales

Just the next group of muscles is the transversospinales muscles, which lie underneath the erector spinae muscles, and the reason they're called transversospinales, if you watch the tutorial on the, on the individual features of the vertebra, you'll remember the transverse process, and the spinous process, and the reason they're called transversospinales muscles is because they connect from the transverse process to the spinous process.

Okay, so there are three transversospinales muscles, you've got the most superficial one is the semispinalis, and then you've got the multifidus, and the most deep transversospinales muscle are the rotares.

 

You’ve got the semispinalis, the multifidus, and the rotares, and those muscles are called the transversospinales because they connect from the transverse process to the spinous process.

 

Just to recap over what I've shown you, just quickly go through it. I've shown you the intermediate, and intrinsic and deep muscles of the back, so the intermediate muscles you've got the serratus posterior superior and inferior, and they are involved in elevating and depressing the ribs. You've got the muscles which move the head and neck: the splenius capitis, which is shown here, and the splenius cervicis which is here, but for some reason isn't on this model. And then you've got the erector spinae muscles, so "I long for spinach": iliocostalis, longissimus, and spinalis. And then deep to those you've got the transversospinales muscles, so you've got the semispinalis, the multifidus, and then you've got the rotares underneath.

 

That’s the intermediate and deep muscles of the back.