Video: Neurovasculature of the shoulder and arm

When going on a road trip in the old days – before we had GPSs and Google maps, that is – the most important tool of any family navigator was their trusty multi-folding road map. Wrestling with one of these in the confined space of a car was no easy task while you stressed out about how not to miss your turn off and figure out which way is up. Did you notice all the different-colored roads? The red major roads, the yellow minor roads, and the big blue highways? Don't you think it looks somewhat familiar to what we see in our anatomy textbooks – red arteries, yellow nerves, and blue veins? These structures are found throughout the body and they supply it with oxygenated blood, innervation, and take deoxygenated blood back to the heart. Collectively, they're known as the neurovasculature, and in today's tutorial, we will focus on the neurovasculature of the shoulder and the arm.

Before we begin, I'd like to give you a quick overview of what we're going to talk about in this tutorial. In our image here, the musculature has been dissected away so that we can see the bones of the shoulder joint and the surrounding neurovasculature from an anterior perspective. This illustration will feature heavily throughout our tutorial as we discuss the arteries, the veins, and nerves of the shoulder and the arm. And, finally, we'll conclude our tutorial with some clinical notes.

Without further ado, let's get started with the arteries of the shoulder and the arm.

In order to orientate ourselves, we're going to start at the beginning. The arterial supply to the shoulder and arm originates in the chest as the subclavian artery. You'll notice that we've removed the veins and nerves from our illustration so that we can see this vessel more clearly. If we zoom out and look at the bigger picture, we can see that the right subclavian arises from the brachiocephalic trunk and the left subclavian arises directly from the aortic arch.

Okay, so let's go back to our previous image. From its origin, the subclavian artery travels laterally passing between the anterior and middle scalene muscles. Along its course, the subclavian artery gives off various branches, but today, we will only focus on the branches that supply the shoulder and the arm.

The thyrocervical trunk arises from the subclavian artery and the reason we're mentioning it is because it gives rise to the suprascapular artery. The suprascapular artery supplies the supraspinatus and infraspinatus, which are muscles of the rotator cuff. When the subclavian artery crosses the lateral border of the first rib, it becomes the axillary artery. So, the axillary artery is a continuation of the subclavian artery.

Along its course, this artery gives off various branches including the superior thoracic artery, the thoracoacromial artery, the lateral thoracic artery, the subscapular artery, the anterior circumflex humeral artery, and the posterior circumflex humeral artery. To remember the branches of the axillary artery, try using the mnemonic Save The Lions And Protect Simba. The first letter of each word in our mnemonic stands for the first letter of a branch of the axillary artery.

The superior thoracic artery doesn't supply the arm or shoulder region so we're going to skip that one and talk about the thoracoacromial artery. This artery has four branches – a clavicular branch, an acromial branch, a pectoral branch, and most relevant for us today, a deltoid branch. The deltoid branch supplies the deltoid muscle that defines the round contour of your shoulder. Next, we have the lateral thoracic artery. This artery is a branch of the axillary artery and supplies the subscapularis, which is a muscle of the rotator cuff as well as the pectoralis major, the pectoralis minor, and serratus anterior muscles.

Next, we can see the subscapular artery highlighted in green. Again, this artery arises from the axillary artery and gives off two branches. The first is the thoracodorsal artery which you can see here, and if we switch to a posterior view, we can see the other one, which is the circumflex scapular artery. This artery supplies the subscapularis, the supraspinatus, and the infraspinatus muscles.

Another branch of the axillary artery which we can see here from an anterior perspective is the anterior circumflex humeral artery. This artery supplies the head of the humerus, the shoulder joint, the teres major, the teres minor, and the deltoid muscle.

Lastly, we have the posterior circumflex humeral artery. This artery anastomoses with the anterior circumflex humeral artery. It supplies the shoulder joint, the teres major, the teres minor, the deltoid, and the triceps brachii which is the main muscle of the posterior compartment of the arm.

When the axillary artery crosses the inferior border of the teres major, it becomes the brachial artery. So the brachial artery is a continuation of the axillary artery and it supplies the muscles of the arm. As this artery travels through the arm, it gives off several branches including the deep brachial artery, the humeral nutrient artery, the superior ulnar collateral artery, the inferior ulnar collateral artery, and various smaller muscular branches.

The first branch of the brachial artery we'll talk about is the deep brachial artery, which is also known as the profunda brachii artery and it gives off various branches including the deltoid branch, the radial collateral artery, and the middle collateral artery.

The deltoid branch travels up the arm and anastomoses with the posterior circumflex humeral artery. This artery supplies the deltoid muscle. The radial collateral artery travels down the arm to anastomose with arteries that form the arterial network of the elbow joint and it supplies the brachialis, which is a muscle of the anterior compartment of the arm. We also have the middle collateral artery. Again, this artery courses down the arm to anastomose with the arteries that form the arterial network of the elbow joint.

Okay, so we've covered the branches of the deep brachial artery. Let's look at the other arteries that arise from the brachial artery.

Here we can see the humeral nutrient artery which, as you've probably guessed, supplies the humerus. The brachial artery also gives off a superior ulnar collateral artery and an inferior ulnar collateral artery. The superior ulnar collateral artery contributes towards the arterial network of the elbow joint. This artery supplies the triceps brachii whereas the inferior ulnar collateral artery supplies the muscles of the anterior compartment of the arm.

In this image, we can see these muscles which include the coracobrachialis, the biceps brachii, and the brachialis. This artery also contributes towards the arterial network of the elbow joint. When the brachial artery reaches the cubital fossa, it splits into two terminal branches – the radial artery and the ulnar artery. These arteries travel down the forearm and anastomose in the hand to form the superficial and deep palmar arches. Before leaving the region of the elbow joint, they both give off recurrent branches, which ascend proximally into the arm, and these are the radial recurrent artery which anastomoses with the radial collateral artery, the anterior branch of the ulnar recurrent artery which anastomosis with the inferior ulnar collateral artery, and the posterior branch of the ulnar recurrent artery which anastomoses with the superior ulnar collateral artery.

Before we go on to talk about the veins of the shoulder and the arm, let's summarize what we've learned about the arteries of the shoulder and the arm.

So the arterial supply begins in the chest as the subclavian artery. The right subclavian arises from the brachiocephalic trunk and the left subclavian arises directly from the aortic arch. When the subclavian artery crosses the lateral border of the first rib, it becomes the axillary artery which gives off various branches. Eventually, the axillary artery passes the inferior border of the teres major and becomes the brachial artery. The brachial artery travels down the arm giving off several branches until it reaches the cubital fossa. Here, it splits into its terminal branches – the radial artery and the ulnar artery.

Alright, now we're ready to move on to the veins of the shoulder and the arm which can be divided into the deep veins and the superficial veins.

In our tutorials, we normally start with the superficial structures first but today we're going to begin with the deep veins as they mirror the arteries of the shoulder and the arm, and for the most part, they do this as venae comitantes. Wondering what that is? Well, venae comitantes is the term used to describe a pair of veins, but occasionally more that closely accompany an artery. This is physiologically advantageous as the pulsations of the artery assist with venous return.

When we describe the arteries, we did so in a way that reflected their delivery of oxygenated blood from the heart to the upper limb, whereas here, we will describe the veins the other way around to demonstrate how they take deoxygenated blood from the upper limb back to the heart. For context, we're going to start in the hand. The superficial and deep palmar venous arches drain into the two veins you can see on your screen – the radial vein and the ulnar vein. Note that in our image, the right arm shows the superficial veins and the left arm shows the deep veins.

The radial and ulnar veins travel up the forearm, and at the level of the cubital fossa, they unite to form the brachial veins. These veins accompany the brachial artery as venae comitantes and their tributaries are similar to the brachial arterial branches. When the brachial vein crosses the lower border of the teres major, it becomes the axillary vein. Again, the tributaries of this vein reflect the axillary arterial branches. The axillary vein travels to the lateral border of the first rib where it becomes the subclavian vein. From its origin, the subclavian vein travels medially passing in front of the anterior scalene muscle.

Let's zoom out now and look at the bigger picture. Here we can see that the subclavian vein receives the external jugular vein before it unites with the internal jugular vein to become the brachiocephalic vein. The left and right brachiocephalic veins merge to form the superior vena cava which returns deoxygenated blood to the right atrium of the heart.

Before we move on to the superficial veins, let's summarize what we've learned about the deep veins of the shoulder and the arm. We started with the palmar venous arches of the hand which drain into the radial and ulnar veins. These veins then unite at the level of the cubital fossa to form the brachial vein. When the brachial vein passes the inferior border of the teres major, it becomes the axillary vein. The axillary vein travels to the lateral border of the first rib where it becomes the subclavian vein. After receiving the external jugular vein, the subclavian vein unites with the internal jugular vein to form the brachiocephalic vein. The left and right brachiocephalic veins then merge to form the superior vena cava which returns deoxygenated blood to the right atrium of the heart.

That's us finished with the deep veins, let's now talk about the superficial veins. Again, we're going to start in the hand with the dorsal venous network. This network drains into two veins we're going to talk about – the cephalic vein and the basilic vein. First, we have the cephalic vein which we can see here highlighted in green. This vein courses up the lateral aspect of the upper limb within the superficial fascia. After passing through the deltopectoral groove, it pierces the deep fascia to drain into the axillary vein.

Now we have the basilic vein which courses up the medial side of the upper limb within the superficial fascia. This vein pierces the deep fascia and drains into the brachial vein forming the axillary vein. The cephalic vein is connected with the basilic vein via the median cubital vein at the elbow. And just a fun fact, we typically use the median cubital vein to draw blood from the cubital fossa.

Let's quickly summarize what we learned about the superficial veins of the shoulder and the arm before we move on to the nerves. We started with the dorsal venous network which drains into the cephalic and basilic veins. The cephalic vein courses up the lateral side of the upper limb to drain into the axillary vein whereas the basilic vein travels up the medial side of the upper limb and unites with the brachial vein to form the axillary vein. The cephalic vein and the basilic vein are linked via the median cubital vein.

Alright, time for our last topic of the tutorial which is the nerves of the shoulder and the arm.

Before we narrow our focus down to specific nerves of the shoulder and the arm, we need to zoom out and look at the bigger picture. The upper arm is innervated by the brachial plexus which we can see here highlighted in green. I'm going to give you a speedy overview of the brachial plexus so you don't look like this when I discuss its branches. However, if you want more detail, we have various other resources you can access on our website.

So, in this image, you can see we have the brachial plexus in isolation. As you can see, the brachial plexus is formed by the anterior or ventral rami of the spinal nerves C5 to T1. These rami give rise to three trunks – the superior trunk, the middle trunk, and the inferior trunk. Each trunk divides into an anterior and posterior division which go on to form three cords – the lateral cord, the posterior cord, and the medial cord.

The nerves that we're going to talk about in this tutorial arise from various levels of the brachial plexus. The first nerve we're going to look at is the suprascapular nerve which arises from the superior trunk of the brachial plexus. This nerve carries fibers from the anterior rami of spinal nerves C5 and C6. Here we can see the bones of the shoulder joint and the suprascapular nerve from a superior perspective. This nerve innervates the supraspinatus and the infraspinatus muscles.

Moving on, we have the musculocutaneous nerve which is a terminal branch of the lateral cord of the brachial plexus. This nerve carries fibers from the anterior rami of spinal nerves C5, 6, and 7. In our next illustration, we can see the bones of the shoulder joint and the musculocutaneous nerve from an anterior perspective. This nerve innervates the coracobrachialis, the biceps brachii, and the brachialis muscle.

Now we're going to look at some branches of the posterior cord of the brachial plexus starting with the upper subscapular nerve, also known as the superior subscapular nerve. This nerve carries fibers from the anterior rami of spinal nerves C5 and 6 and innervates the superior portion of the subscapularis muscle. Next, we have the thoracodorsal nerve, which is also known as the middle subscapular nerve. This nerve arises from the posterior cord and carries fibers from the anterior rami of spinal nerves C6, 7, and 8. The thoracodorsal nerve innervates the latissimus dorsi muscle which inserts at the proximal humerus. The lower or inferior subscapular nerve also arising from the posterior cord innervates the inferior portion of the subscapularis and the teres major muscle. This nerve carries fibers from the anterior rami of spinal nerves C5 and C6.

Okay, so let's look now at the terminal branches of the posterior cord – the axillary nerve and the radial nerve. Here, we have the axillary nerve, which is also known as the circumflex nerve. This nerve carries fibers from the anterior rami of spinal nerves C5 and C6. The axillary nerve innervates the deltoid and teres minor muscles as well as the skin overlying the deltoid muscle.

The other terminal branch of the posterior cord is the radial nerve. It is the largest nerve in the upper limb and carries fibers from the anterior rami of spinal nerves C5 to T1, so it receives fibers from all five spinal nerves of the brachial plexus. The radial nerve directly innervates the triceps brachii, the anconeus, and contributes towards the innervation of the brachioradialis muscle.

It provides sensory innervation to the skin of the posteromedial and posteroinferior aspect of the arm, as well as a strip of skin down the middle of the posterior forearm. The deep branch, also known as the motor branch, provides motor innervation to the posterior compartment of the forearm. While the superficial branch, also known as the sensory branch, provides sensory innervation to the thenar eminence and the dorsal aspect of the radial 3 and 1/2 digits of the hand.

So far, we've focused primarily on nerves that supply the muscles and the bones of the arm, but what about the skin? Well, that's where the brachial cutaneous nerves come in. There are four of these nerves and the first one we'll talk about is the medial cutaneous nerve of the arm. This nerve is a branch of the medial cord of the brachial plexus and innervates the skin of the medial arm. Next, we have the superior lateral cutaneous nerve of the arm. This nerve is a branch of the axillary nerve and innervates the skin overlying the deltoid muscle.

If we have a superior lateral cutaneous nerve of the arm, then we must have an inferior lateral cutaneous nerve of the arm. This nerve is a branch of the radial nerve and innervates the skin of the lateral lower arm. The last brachial cutaneous nerve is the posterior cutaneous nerve of the arm. This nerve is also a branch of the radial nerve and innervates the skin of the posterior surface of the arm.

For the sake of completeness, I'm going to briefly mention the nerves that innervate the forearm and the hand starting with the median nerve. As you can see in our illustration, this nerve is made up of fibers from the lateral cord and the medial cord of the brachial plexus. The median nerve carries fibers from the anterior rami of spinal nerves C6 to T1. Lastly, we have the ulnar nerve which is the terminal branch of the medial cord. It carries fibers from the anterior rami of spinal nerves C8 and T1, and like the median nerve, it innervates the forearm and the hand.

Before we talk about some clinical notes relating to the neurovasculature of the arm, let's summarize what we've learned about the nerves of the shoulder and the arm. First, we looked at the brachial plexus which consists of the anterior rami of the spinal nerves C5 to T1; three trunks – the superior trunk, the middle trunk, and the inferior trunk; and three cords – the lateral cord, the posterior cord, and the medial cord. We saw that the superior trunk gives rise to the suprascapular nerve and that the musculocutaneous nerve is a terminal branch of the lateral cord. We also learned that the posterior cord gives rise to the upper subscapular nerve, the thoracodorsal nerve, the lower subscapular nerve, the axillary nerve, and the radial nerve. Next, we talked about the four brachial cutaneous nerves of the arm which are the medial cutaneous nerve of the arm, the superior and inferior lateral cutaneous nerves of the arm, and the posterior cutaneous nerve of the arm. Finally, we briefly mentioned the nerves that innervate the forearm and hand which are the median nerve and the ulnar nerve.

Now that we're familiar with the neurovasculature of the shoulder and the arm, let's get clinical.

Since the radial nerve is the largest nerve in the upper limb, let's talk about it in our clinical notes. Radial nerve injury is most commonly caused by physical trauma such as a humeral fracture. Symptoms commonly present in the thumb, index, and middle fingers and include numbness and tingling or burning pain. Radial nerve injury can also result in weakness in the wrist and fingers as well as an inability to straighten the arm. The last two symptoms relate to muscles that are innervated by the radial nerve such as the extension of the wrist and the fingers and the triceps brachii which extends the elbow.

Treatment varies depending on the underlying cause but can include anti-inflammatory medications to relieve pain and physiotherapy to build and maintain muscle strength. A brace or splint may be used to immobilize the nerve allowing it to heal without risk of further damage. If the nerve isn't torn or lacerated, patients should recover within three months. However, surgery may be also required to repair damage to the nerve.

Before we bring our tutorial to a close, let's quickly summarize once again what we've learnt today.

We started with the arteries of the shoulder and arm following the journey oxygenated blood takes from the heart into the upper limb. We saw that the arterial supply starts with the subclavian artery which becomes the axillary artery at the lateral border of the first rib. When the axillary artery passes the inferior border of the teres major, then it becomes the brachial artery. The brachial artery travels down the arm until it reaches the cubital fossa where it splits into its terminal branches – the radial artery and the ulnar artery. These arteries course down the forearm and anastomose in the hand to form the palmar arches.

Next, we looked at the veins of the shoulder and arm which can be grouped into deep veins and superficial veins. Similarly, we discussed these vessels in an order that reflected how deoxygenated blood is returned from the upper limb to the heart. The deep veins mirror the arteries of the shoulder and the arm and include the palmar venous arches, the radial vein, the ulnar vein, the brachial vein, the axillary vein, and of course, the subclavian vein, whereas the superficial veins consist of the dorsal venous network, the cephalic vein, the basilic vein, and the median cubital vein.

We then looked at the nerves of the shoulder and the arm which arise from various levels of the brachial plexus. The brachial plexus consists of the anterior rami of the spinal nerves C5 to T1; three trunks – the superior trunk, the middle trunk, and the inferior trunk; and three cords – the lateral cord, the posterior cord, and the medial cord. We saw that the superior trunk gives rise to the suprascapular nerve and that the musculocutaneous nerve is a terminal branch of the lateral cord. We also learned that the posterior cord gives rise to the upper subscapular nerve, the thoracodorsal nerve, the lower subscapular nerve, the axillary nerve, and the radial nerve.

Next, we talked about the four brachial cutaneous nerves of the arm which are the medial cutaneous nerve of the arm, the superior and inferior lateral cutaneous nerves of the arm, and the posterior cutaneous nerve of the arm. We also briefly mentioned the nerves that innervate the forearm and hand which are the median nerve and the ulnar nerve. Finally, we finished up our tutorial with some clinical notes about radial nerve injury.

So that brings us to the end of our tutorial on the neurovasculature of the shoulder and the arm.

I hope you enjoyed it. Thanks for watching and happy studying!