Muscles of the Back (Nursing)

by Darren Salmi, MD, MS

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    00:01 If we have movements, there must be some muscles involved.

    00:05 So we'll talk now about the muscles of the back.

    00:08 And we're gonna go from superficial to deep.

    00:12 And we're going to start with a superficial layer, because they're not really what we might consider typical back muscles in the sense that they don't really move the back.

    00:21 They really act on the upper limb.

    00:23 So they're really something that is involved in upper limb movements.

    00:27 But we'll mention them anyway, because they're located in the back.

    00:32 For example, we have this roughly diamond-shaped structure here called the trapezius.

    00:38 And this one's going from the base of our skull, along our spinous processes of those vertebra, unto a bone in a portion of bone called the spine of the scapula we'll learn about in the upper limb.

    00:51 And so that's going to be helpful for shrugging our shoulders for example.

    00:55 There are also these muscles called the rhomboids that are going to connect our spinous processes to the medial edge of that bone, we'll learn later called the scapula.

    01:06 And when it contracts, it's going to retract or pull our scapula towards the midline.

    01:12 And then this large broad flat one is called the latissimus dorsi.

    01:18 And it's running along the super spinous processes out to the humerus, which is the bone of our upper limb.

    01:25 And that's really going to cause a lot of adduction at our shoulder joint.

    01:31 If we go a little bit deeper, though, to a middle layer of muscles, now we're getting into muscles that act on the back more directly, more classic back muscles.

    01:42 The first ones we see are running vertically on either side of the vertebral column, and they're called the erector spinae group.

    01:50 And erector kind of gives you some idea kind of sounds like moving up, you're getting straight, and that's going to extend the back.

    02:00 And they're very similar if we look superiorly with another group that almost blends with it called the splenius group, which is going to do the same thing but more in the cervical area.

    02:10 And so that's going to be more neck extension.

    02:14 Finally, if we go really deep to the deepest layer, where we're just connecting between tiny little portions of the vertebral column itself.

    02:23 We have some small ones and we'll point out two there's Multifidus and Rotatores.

    02:29 And multifidus just means many and that's probably not helpful.

    02:31 But rotatores probably gives you some idea of what it's doing.

    02:34 And multifidus is really stabilizing the spine.

    02:38 And rotatores really a small one helping with our rotational movement.

    02:43 If we go so deep that we're not even in the back anymore, but we're reaching the posterior abdomen.

    02:49 We'll talk about some other muscles that really aren't back muscles but are important to just know that they're nearby.

    02:56 So if we go all the way through the back, we reach a muscle that's in the posterior abdomen called the quadratus lumborum.

    03:04 And that's going to connect to the top of our pelvic bones called the iliac crest and our bottom rib the 12th rib and it's going to also connect to our lumbar vertebra.

    03:16 So not everything connects to the vertebra our back muscles necessarily.

    03:22 And it's going to do some of the movements we mentioned already, such as the lateral flexion of the vertebral column.

    03:28 Similarly, on the other side, we have a muscle that we're gonna learn about in the abdomen called transversus abdominus.

    03:34 It's definitely not a back muscle, it's an abdominal muscle.

    03:37 But we can see that it wraps all the way around to the back.

    03:43 If we go to an anterior point of view, we have these large muscles here are called the iliopsoas.

    03:49 And they're also attaching to the lumbar vertebra despite not being back muscle.

    03:55 And they're actually hip flexors.

    03:57 And when we talk about the lower limb, we'll see they're very strong hip flexors.

    04:01 But they can act on the trunk as well, if for example, you fix the feet, and then you flex this muscle, instead of moving at the hips and moving the leg upward, it's going to move the torso.

    04:14 So it's essentially like if you were lying down on the ground, and you had someone sitting on your feet, and you activated your iliopsoas, you would do a sit up, and it would seem as if you're moving your torso.

    04:26 And so this kind of brings us to this concept of the core, it's a very nebulous thing that really isn't just back muscles.

    04:34 We think of the core is something that provides a lot of stability to our torso and our body overall.

    04:39 And there are a lot of back structures that are a part of it, such as multifidus, and in bony terms, the sacrum.

    04:47 But we also have abdominal muscles anteriorly and other structures in the pelvis, like the pubic symphysis we'll learn about that are also part of the core and basically complement the stuff that we've learned in the back.

    05:00 So for example, we see some of them here, we see that abdominal muscle transversus abdominis.

    05:05 Even though it's an abdominal muscle, it goes all the way around to the back, and it connects to our back fascia.

    05:11 So in a lot of ways, it's hard to really separate abdominal and back function.

    05:16 We can see it's also connecting to the lower ribs connecting to our thorax.

    05:20 It's connecting to this bone that we're going to learn called the illum that's in our pelvis, and really is helping connect everything hence the term core.

    05:29 And what the core does, in this sense is also compressing and supporting our abdominal wall in addition to our back and helping make sure everything's stabilized and essentially using as little energy as possible to keep us in a nice neutral position.

    About the Lecture

    The lecture Muscles of the Back (Nursing) by Darren Salmi, MD, MS is from the course Anatomy of the Musculoskeletal System (Nursing).

    Included Quiz Questions

    1. Trapezius
    2. Rhomboids
    3. Latissimus dorsi
    4. Erector spinae group
    5. Splenius group
    1. Erector spinae group
    2. Splenius group
    3. Trapezius
    4. Rhomboids
    5. Quadratus lumborum
    1. Multifidus
    2. Rotatores
    3. Trapezius
    4. Erector spinae group

    Author of lecture Muscles of the Back (Nursing)

     Darren Salmi, MD, MS

    Darren Salmi, MD, MS

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