Hello, everyone. This is Joao from Kenhub, and welcome to another anatomy tutorial where, this time, I'm going to be talking about the neurovasculature of the forearm.
What I'm going to be doing here today is talking about the different arteries, different veins, and also nerves that you find on the forearm region. To be a bit more visually specific, I'm showing you right now the different arteries, veins, and nerves that you can actually find on the forearm.
And before we start talking about them, I want to just list the different structures that we will talk about. And the first one is the different arteries that can be found on the forearm, including the common interosseous that is seen now on the list. The other one is the anterior interosseous, and the posterior interosseous artery is also part of the arteries that you find on the forearm, and finally, the radial recurrent.
Now, in terms of veins, we can find the cephalic vein, also the basilic vein, and the median cubital vein.
For the nervous supply of the forearm, we want to show you the cutaneous nerves being responsible for the sensory input on this area, but the motor nerves of the brachial plexus can be also found in the neurovasculature of the upper arm tutorial. So we’re also going to be covering them.
But just to list a few of the nervous supply that you find on this area, we’re going to see an anterior antebrachial forearm region, which have the following structures: the lateral cutaneous nerve of the forearm and also the medial cutaneous nerve of the forearm.
On a posterior antebrachial or forearm region, we are going to find, then, the posterior cutaneous nerve of the forearm from the radial nerve, and also the posterior branches of the medial and lateral antebrachial cutaneous nerves.
And we are also going to see on the posterior forearm region another nerve known as the superficial branch of the radial nerve.
Now that we listed all the structure that we’re going to be talking about on this tutorial, it is time for us to start off with an artery if you remember well from the first list that we talked about. This one, highlighted in green, is known as the common interosseous artery. Now, the common interosseous artery is only around... it’s about one centimeter long—so it’s not too long—and comes out of the ulnar artery at the radial tuberosity.
Now, you can clearly see here the radial tuberosity and then the common interosseous branching off the ulnar artery right here.
Now, still on the common interosseous, it is important to know that this artery is going to run dorsally between the radius and the ulna, hence the name. The name says everything. “Interrosea” in Latin means “between bones,” and you can clearly see here on this image that the common interosseous is running between the radius and the ulna.
And it runs so to the, then, upper edge of this membrane here known as the interosseous membrane. And again, interosseous meaning that it’s between a membrane existing between the radius and the ulna.
And from there, the common interosseous is going to divide into, then, the anterior interosseous and the posterior interosseous, which will be the next arteries that we’re going to talk about.
Let’s move on, then, to this one now, highlighted in green, which is, then, the anterior interosseous that branches off of the common interosseous artery as I mentioned before. And this artery runs down the forearm ventrally to the interosseous membrane as you can clearly see here on this image accompanied by the anterior interosseous nerve. And during its course, it gives several small branches to the nearby muscles, the radius, and also to the ulna.
We would not finish this tutorial without the, then, posterior interosseous artery that is now seen on the screen, highlighted in green. And the posterior interosseous artery is very similar to the anterior one. It is also a continuation of the common interosseous artery and runs down the forearm just dorsally to this membrane that we talked about, the interosseous membrane. And now you can clearly see here the interosseous membrane just behind… or in this case, anteriorly to the posterior interosseous, because keep in mind now, we’re looking at the posterior view of the forearm.
With its small branches, it also supplies the dorsal muscles of the forearm—so something important to highlight—and will give off the interosseous recurrent artery which, then, will supply the elbow joint.
Now, before I move on to another artery, I want to mention something about the anterior interosseous and also the posterior interosseous that at the distal dorsal side of the forearm, the anterior and posterior arteries, or the anterior and posterior interossi arteries will meet and form an anastomosis in order to grant an efficient network of blood supply for the whole forearm region, so important thing to mention on how these... or on the importance and also function of the anterior and posterior interossi arteries.
We’re going to move on and talk about another one, now seen here highlighted in green. This is known as the radial recurrent artery. It is also another interesting small artery, and it branches from the radial artery forming an anastomosis with the deep brachial artery. And you can clearly see here the radial artery and then an anatomosis with the brachial artery.
If the deep brachial artery is blocked or damaged, the lower arm can still be supplied with an arterial blood, with arterial blood, by this anastomosis via the deep brachial artery. So this is an important clinical point that you might want to write down on your notes. And also, important to mention that this artery will supply the elbow joint with blood.
We’re going to move on and start talking about the different veins of this region of your body, the forearm. And you see now, them highlighted in green. The basilic vein on the left side, on the image on the left side, while you see on the image on the right side, the cephalic vein, highlighted in green.
Now, the venous blood flow towards the heart is enabled in this region by these two veins, the basilic and the cephalic. They start at the hand on the venous network of the hand, dorsal venous network, and run into the upper arm and then follow... take the deoxygenated blood all the way back to the heart. It’s a long journey as you can see. Now, both are connected by this vein here that is known as the median cubital vein.
Now, let’s start with the very first one here. If you remember from the previous list, yes, this is the basilic vein. And the basilic vein is a... is going to drain into the axillary vein. Keep that in mind. So we’re looking at it as if it goes from here, the origin being on the dorsal venous network and… of the hand, and then goes all the way back taking blood into the heart.
Because when we talk about arteries, we usually mention the direction… the branches based on the direction of the blood. So it goes from the heart all the way to the extremities. Then what happens when we talk about the different blood vessels, the different veins, we talk about as the blood goes back to the heart. So it starts then on the venous network of the hand, and then it’s going to drain to the axillary vein. So I'm adding here that it starts at the dorsal venous network of the hand—two things to remember about the basilic vein.
Now, in terms of the cephalic vein that you’re now seeing on the screen, highlighted in green, it is also important to mention that it’s going to drain into the axillary vein and runs on the radial side of the lower arm as it comes out of the dorsal venous network of the hand. So starts at the dorsal venous network of the hand and then drains into the axillary vein—two important points about the cephalic vein.
Now, one vein that I mentioned before that connects the cephalic and the basilic vein is the, then, the median cubital, now seen highlighted in green. What you need to know is that it lies superficial in the cubital fossa and connects, then, the basilic and cephalic veins. It is a typical vein chosen for blood drawing from this area, from the cubital fossa.
Now, we’re going to talk about the different nerves, and the first one that we’re seeing here, highlighted in green, is known as the lateral cutaneous nerve. Now, the lateral cutaneous nerve of the forearm is a branch of... this nerve that you’re seeing, highlighted in green, the musculocutaneous nerve. It passes behind the cephalic vein and divides opposite the elbow joint into a volar and dorsal branches.
Now, if we talk about briefly about the volar branch or anterior branch, it descends along the radial border of the forearm to the wrist and supplies the skin over the lateral half of the forearm’s volar surface.
Now, a brief note here on the dorsal branch, also known as the posterior branch of the lateral cutaneous nerve, this descends along the dorsal surface of the radial side of the forearm to the wrist, and it supplies the skin of the lower two-thirds of the dorsal lateral surface of the forearm.
We’re going to move on to another nerve seen highlighted in green. This is known as the medial cutaneous nerve. And the medial cutaneous nerve of the forearm arises from the medial cord of the brachial plexus. Also important to mention that it splits into a volar and also ulnar branches. And on the volar branch, what you need to know—or also known as anterior branch—this is the larger and passes usually in front but occasionally behind the median cubital vein. It distributes filaments to the skin as far as the wrist.
We’re moving on and talking about another nerve seen highlighted here in green. This is the posterior cutaneous nerve. The posterior cutaneous nerve of the forearm arises from this one that you see, highlighted in green, the radial nerve in the posterior compartment of the arm. Also important to add here about the posterior cutaneous nerve is that it supplies the posterior side of the forearm and wrist.
Moving on, we’re going to talk about this one that you see now highlighted in green. This is known as the superficial branch of the radial nerve. And the superficial branch of the radial nerve passes along the front of the radial side of the forearm to beginning... to the beginning of its lower third. It is a sensory nerve—keep that in mind.
Now, the lateral branch of the superficial branch of the radial nerve is the smaller one and supplies the skin of the radial side of the ball of the thumb.
Now, important to mention that the medial branch is going to divide into, then, four digital nerves: the first one being on the ulnar side or supplying the ulnar side of the thumb, while the second one is going to be, then, supplying the radial side of the index finger. The third one is going to be the adjoining sides of the index and middle fingers, while the fourth one is the adjacent sides of the middle and ring fingers.
