Today’s video will teach you a simpler way to learn about the nerves of the brachial plexus. From the roots, trunks, divisions, to the cords and branches, Leslie Samuel shows you another effective way to remember the things you need to know about the anatomy of the brachial plexus.
Transcript of Today’s Episode
By the end of this video, you’ll know exactly what the brachial plexus is and not only that. You’ll also be able to draw the brachial plexus with all of the nerves that are involved. So, let’s get right into it.
Alright, so here, we’re looking at the brachial plexus. The brachial plexus is basically a network of nerves coming from the ventral rami of C5 through T1. So, here we can see C5, C6, C7, C8, and T1. We have some nerve roots that are coming from those ventral rami.
If we look at a cross-section of the spinal cord, here you can see the spinal cord, and here you can see the vertebrae, we have a ventral ramus and a dorsal ramus at each level.
On the ventral end, we have the motor output. These are the motor fibers, motor neurons that are innervating the muscles of the upper extremities. The way I remember this is M-O-V-E. Alright, to MOVE, we have:
M – Motor
O – Output
V – Ventral
E – Efferent
So, it’s motor fibers. Their output they’re going away from the nervous system.They’re coming from the ventral rami and they’re considered efferent fibers.
On the opposite end, on the dorsal side, we have SIDA. That’s not a word like MOVE so, it’s not as cool but you know it’s exactly opposite:
S – Sensory
I – Input
D – Dorsal
A – Afferent
So, “motor, output, ventral, efferent,” that’s what we’re dealing with in this video. “Sensory, input, dorsal, afferent,” that’s a topic for another video. So, let’s focus on the MOVE right now. We’re going to look into more detail when it comes to the brachial plexus and that’s exactly what we have here.
Now, you’re seeing much more detail. You’re seeing the roots, the trunks, the divisions, the cords, and it’s not listed here, but I’m going to put it in. I’m going to put my own dotted lines since this doesn’t have it. I’m going to put branches.
Alright, roots, trunks, divisions, cords and branches. These are going to form the nerves that are innervating the muscles of the upper extremities. We’re starting with the roots and then, we’re going to have some combining to form trunks and then, we’re going to have some divisions and cords and branches. The way I remember these is RTDCB. That doesn’t mean so much right now. That stands for:
R – Robert
T – Taylor
D – Drinks
C – Cold
B – Beer
If you can remember that, you can remember,
R – Roots
T – Trunks
D – Divisions
C – Cords
B – Branches
Simple mnemonic device that you can use for remembering the sequence. So, we’re starting with the roots and we’re ending up with branches.
You can see it’s a complex network of nerves that are combining and branching off and so on, and it can look quite intimidating when you look at it like this. But, what we’re going to do is we’re going to break it down. I want you to take out a plain sheet of paper, a white sheet of paper, or something that you can draw on and we’re going to break this down so that, by the time you finish this video, you’ll have a strategy that you can use and you can spend about 30 minutes to an hour maximum and you’ll have this perfected.
If you don’t have a blank sheet of paper in front of you right now, you can pause this video and then, come back to it. I’m going to go through these steps, and you can pause as I go through these steps so that, you can follow along and do exactly what I’m showing you.
So, first, what I want you to do is that the top right of the paper, I want you start with these five lines coming down at an angle just like this. I want you to label them C5, C6, C7, C8, and T1. These are the five roots. That’s what we’re starting with. Draw these five lines.
Then, the next thing I want you to do, the top two we’re going to combine, and the bottom two we’re going to combine. When we combine them, I’m going to extend the lines so that, we have the superior trunk, the middle trunk and the inferior trunk. This is exactly what I want you to do. Extend the lines to form the three trunk. So, we have “R-Robert, T-Taylor,” the roots and the trunks.
Next, we have “Robert Taylor DRINKS,” that’s going to be the divisions. This is going to be the first part where they split and they’re all going to split into two divisions, the anterior and posterior divisions. This is exactly what I want you to do. Draw that on your paper — anterior and posterior divisions. If you need to pause as I’m doing this, feel free to do so, but I want you to walk through this with me.
Then, what’s going to happen, the upper two anterior divisions are going to combine to form the lateral cord. So, “Robert Taylor Drinks COLD,” C is for cords. So, we’re going to combine the anterior divisions to form the lateral cord.
All of the posterior divisions are going to join together to form the posterior cord. Then, we have one that’s left over, the anterior division from the inferior trunk is going to go on to form the medial cord. We have the lateral cord, the posterior cord, and the medial cord.
These are named in reference to the axillary artery that’s passing right along here. This is going to be posterior to the axillary artery. This is going to be lateral to the axillary artery and, this cord is going to be medial to the axillary artery.
Alright so, once we form these three cords, we’re going to get the second branching off and that’s going to give us the lateral and medial branches of all the cords, the lateral cord, the posterior cord and the medial cord are all going to branch into the lateral and medial branches. Alright, so this is the second time where we have branching. We have branching over here into anterior and posterior, and now we have branching over here into lateral and medial. So, I want you to draw that out.
The next thing we’re going to do is we’re going to form a big “M.” This is the big M that we’re going to form and you could see here, we combine the medial branch of the lateral cord, and the lateral branch of the medial cord to form the median nerve.
We have our median nerve right here in the middle, and here we have MC and U. The way I remember this is this big M, we can picture it as an emblem or a logo for “Mickey Mouse University.”
MC – Mickey
M – Mouse
U – University
These are the:
MC – Musculotaneous nerve
M – Median nerve
U – Ulnar nerve
“Mickey Mouse University.” I want you to draw that out just like I’m doing it here.
Then, the lateral and medial branches of the posterior cord are going to extend and we’re going to form the axillary nerve and the radial nerve. This is the core of the brachial plexus here. We have some other branches to add on, some other nerves that are going to come off in different places. This is how I want you to remember them.
I want you to remember them as four groups of threes. The first group of threes are going to come from the first three roots. You can see them over here. The first three roots are going to combine to form the long thoracic nerve. First three roots combine to form the long thoracic nerve.
Then, the next group of three are going to come from this three un-branched regions at the top, and you can see them here, here, and here. That’s going to be the dorsal scapular nerve, the suprascapular nerve, and the lateral pectoral nerve. This is the second group of three. I want you to draw this out just like I’m doing.
It looks like a lot but, you’re going to do this over and over and over for about 30 minutes and then, you’re going to get this and you’ll know all the nerves of the brachial plexus, at least all the one that we’re going to go over.
The next group of threes, the third group of threes are going to be on the posterior cord, and that’s going to be the upper subscapular and the lower subscapular nerves. In between that, we’re going to get the thoracodorsal nerve.
Alright, upper subscapular, lowe subscapular, and thoracodorsal. That’s the third set of three.
Then, the last set of threes are going to be the medial pectoral nerve, medial brachial nerve, and medial antebrachial cutaneous. That is our fourth group of threes.
Once we’ve done that, we only have one more nerve to add to the mix. That is the nerve to subclavius that you can see over here.
What I want you to do with your blank sheet of paper, you’re going to pull out multiple blank sheet of papers, and you’re just going to go through that same sequence. Rewind this video and do it over and over and over and you’ll get the entire brachial plexus down.
I’m not giving you details as to what these different nerves are innervating as yet. We’re going to get into some of that in later videos. But, in the end, these are all of the branches that we have, sixteen branches coming off of this brachial plexus:
- Long thoracic nerve
- Dorsoscapular nerve
- Nerve to subclavius
- Suprasacpular nerve
- Lateral pectoral nerve
- Upper and lower subscapular nerves
- Thoracodorsal nerve
- Medial pectoral nerve
- Medial brachial cutaneous nerve
- Medial antebrachial cutaneous nerve
- Musculocutaneous nerve
- Axillary nerve
- Median nerve
- Radial nerve
- Ulnar nerve
That’s pretty much it for this video. If you’re enjoying this video, please, right beneath this video, you can click on like and of course, you can subscribe to the channel by clicking on the subscribe button at the top of the video.
But, the most important part is for you to come back over to the website, interactive-biology.com for more Biology videos and other resources to help make Biology fun. This is Leslie Samuel. That’s it for this video and I’ll see you in the next one.