Lab 17: Neves and Vasculature of the Upper Extremity

Learning Objectives:

By the end of this lab, students will be able to:

  • Identify the brachial plexus, its branches, and what structures those branches innervate.
  • Identify the vasculature of the upper extremity.

Terms to Know

Arteries of the Upper Extremity

  • Subclavian artery
    • Suprascapular artery
  • Axillary artery
    • Superior thoracic artery
    • Thoracoacromial artery
    • Lateral thoracic artery
    • Anterior circumflex humeral artery
    • Posterior circumflex humeral artery
    • Subscapular artery
      • Thoracodorsal artery
      • Circumflex scapular artery
  • Brachial Artery
    • Deep Brachial Artery
  • Radial artery
  • Ulnar artery
  • Superficial and Deep palmar arches
  • Digital arteries

Veins of the Upper Extremity

  • Cephalic vein
  • Basilic vein
  • Median cubital vein
  • Brachial vein
  • Axillary vein
  • Subclavian vein
 

Brachial Plexus

  • Dorsal scapular nerve
  • Long thoracic nerve
  • Suprascapular nerve
  • Posterior cord
    • Lower subscapular nerve
    • Thoracodorsal nerve
    • Upper subscapular nerve
  • Medial cord
    • Medial antebrachial cutaneous nerve
    • Medial brachial cutaneous nerve
    • Medial pectoral nerve
  • Lateral cord
    • Lateral pectoral nerve
  • Terminal branches
    • Axillary nerve
    • Median nerve
    • Musculocutaneous nerve
    • Radial nerve
    • Ulnar nerve

 

 


Introduction

Today in lab you will discuss the brachial plexus, the arteries of the pectoral region and the neurovasculature of the elbow, wrist and hand. You will have various tools available to you in the lab to explore the structures listed above. Using the iPads, you will be able to examine and the neurovasculature of the upper extremity. Another activity is designed to help you learn the branches of the brachial plexus and the muscles that these branches innervate. Finally, you will use the cadaveric specimens to view the neurovascualture of the upper extremity.

Lab Activities

Activity 1: Neurovasculature of the upper extremity on the cadaveric tissue and images

You have already identified all of the muscles of the upper extremity. Now you will explore the vessels and nerves that supply and innervate the upper extremity. Remember to use landmarks to help you identify the neurovasculature! For example, if you know which muscles are innervated by a specific nerve, and you follow a nerve to that muscle, you can identify that nerve.

Nerves of the upper extremity:

  • In general, your first step should be looking for the “M” formed by the parts of the medial and lateral cords coming together to form the median nerve. This will help you get your orientation of what is medial and what is lateral. Once you know which is the medial or lateral cord, you can narrow down the branches that would be coming from them. The M sits just anterior to the axillary artery. This also makes it easier to identify the posterior cord sitting posterior to the “M” and the axillary artery.
  • Notice where the nerves are running to. If you know the muscles they innervate, and you can see them entering that muscle, you will be able to identify which nerve it is.
  • Here are a few tips for specific nerves in the axillary region:
    • Dorsal scapular nerve: This nerve is not present on the cadaveric tissue, but you will be able to identify it in images. This nerve will emerge very early from the brachial plexus, near the neck, and you will be able to see it running posteriorly to the rhomboids and levator scapulae.
    • Suprascapular nerve: This nerve will run posteriorly from the brachial plexus towards the scapula. It runs through the suprascapular notch inferior to a ligament forming a bridge across the notch (called the transverse scapular ligament) to reach the supraspinatus, and then through the spine of the scapula to reach the infraspinatus. In the deep dissection, this nerve has been dissected through its entire path to the infraspinatus. Be sure to observe this on the cadaveric tissue.
    • Lateral pectoral nerve: This nerve may not be present in the cadaveric tissue. On an image you may see it run from the brachial plexus to the pectoralis major. You can also know that it is the lateral pectoral nerve, rather than the medial, because it will branch off of the lateral cord.
    • Medial pectoral nerve: This nerve also may not be present in the cadaveric tissue. This nerve is usually the first branch from the medial cord, and it runs through the pectoralis minor, innervating it on its path to the pectoralis major.
    • Medial brachial and medial antebrachial cutaneous nerves: These nerves will branch distal to the medial pectoral nerve off of the medial cord. They run to the skin of the medial arm and forearm. One of these is present in the cadaveric tissue, but we cannot tell which it is because it is cut, and we cannot follow it to its destination. These are visible on the plastinated tissue, superficial to the muscles.
    • Long thoracic nerve: This nerve is easy to spot in images, as it runs tight to the thoracic wall, innervating the serratus anterior muscle. This is also visible running with the serratus anterior on the superficial dissection.
    • Thoracodorsal nerve: This nerve can be seen branching off of the posterior cord and running to the latissimus dorsi muscle.
    • Upper subscapular and lower subscapular nerves: These nerves branch from the posterior cord, with the upper branching proximal to the thoracodorsal nerve and the lower branching distal to the thoracodorsal nerve, in most cases. They run posteriorly to the subscapularis and teres major (lower only) muscles. These are also clearly visible on the pastinated specimen.
    • Axillary nerve: This nerve branches from the posterior cord and runs posterolaterally. It travels with the posterior circumflex humeral artery through a space between the surgical neck of the humerus, the long head of the triceps, teres minor, and teres major to reach the deltoid.
    • Radial nerve: This nerve branches from the posterior cord and runs to the posterior side of the arm. It is larger than the axillary nerve.
    • Ulnar nerve: The ulnar is the most medial branch of the brachial plexus, branching from the medial cord. It continues along the medial side of the arm, and passes around the medial epicondyle of the humerus on its path to the forearm. This nerve is responsible for our “funny bone.” You can also see it enter the hand and send branches to the skin of the 5th digit and lateral aspect of the 4th digit. It also innervates the majority of muscles in the hand, except the thenar eminence muscles and lateral two lumbricals. On the plastinated specimen this a bit challenging to discern in the brachium (arm), but it is clear traveling around the medial epicondyle into the forearm and hand.
    • Median nerve: In the axilla, the median nerve is evident as the middle nerve formed from the “M” of the brachial plexus, as it receives contributions from both the medial and lateral cords. It travels through the anterior arm and forearm to enter the hand and supply the skin of the lateral half of the 4th digit and digits 1-3, as well as the muscles of the thenar eminence and lateral two lumbricals. This nerve is also clearly visible on the plastinated specimen.
    • Musculocutaneous nerve: The musculocutaneous nerve pierces (and supplies) the coracobrachialis muscle in the arm and then runs between the biceps brachii and brachialis muscles. It emerges on the lateral aspect of the arm as the lateral antebrachial cutaneous nerve. Be aware that the medial cord on the deep dissection abnormally pierces the coracobrachialis muscle, then sends its contribution to the median nerve. The musculocutaneous nerve then pierces coracobrachialis again and follows its normal path. While this branching pattern is abnormal, anomalies like this occur frequently with nerves and arteries. In the plastinated tissue this nerve is not visible in the brachium. However, you can see it emerge in the forearm as the lateral antebrachial cutaneous nerve, where it innervates the skin of the lateral forearm.

Arteries:

  • Subclavian artery: This is the primary artery providing the arm with blood. This is not visible on the cadaveric specimens, but it is visible in images.
  • Axillary artery: This artery is continuous with the subclavian artery from the lateral border of the first rib to the inferior border of the teres major muscle. There are several branches you should be able to identify off of the axillary artery.
    • Suprascapular artery: The origin of this artery has been cut, but you can observe it in the deep dissection running over the transverse scapular ligament of the suprascapular notch and traveling to the supraspinatus. This artery runs posteriorly with the suprascapular nerve to supply the supraspinatus and infraspinatus.
    • Superior thoracic artery: This is the only branch off of the first part of the axillary artery. It will run inferiorly to the superior thoracic wall. It has been cut in the dissections, so you cannot follow it to its destination. It may be seen on images.
    • Lateral thoracic artery: This artery branches from the second part of the axillary artery and runs with the long thoracic nerve along the lateral thoracic wall to supply the lateral wall and the serratus anterior. Don’t confuse the lateral thoracic artery and long thoracic nerve! This can be observed in images.
    • Thoracoacromial trunk: This is a short trunk off of the superior side of the second part of the axillary artery. It branches almost immediately into four parts that supply the acromion, deltoid, pectoral muscles, and clavicle. You can see its branches traveling to the pectoralis muscles. However, the other branches of this trunk have been cut in the cadaveric tissue.
    • Posterior and anterior circumflex humeral arteries: These arteries branch from the third part of the axillary artery. They wrap around the surgical neck of the humerus and anastomose (join) with each other to provide circulation to this region via multiple routes. They sometimes branch from a common trunk, or they can branch separately from the axillary artery. Either way, the posterior circumflex humeral artery runs posteriorly around the humerus with the axillary nerve, while the anterior circumflex humeral artery runs anteriorly around the humerus.
    • Subscapular artery: The subscapular artery is a short branch off of the third part of the axillary artery. As it runs inferiorly, it gives off two branches, both of which are visible on the cadaveric tissue. You can also observe these on the plastinated tissue.
      • Circumflex scapular artery: This runs posteriorly around the lateral scapula.
      • Thoracodorsal artery: This artery runs with the thoracodorsal nerve to the latissimus dorsi muscle.
  • Brachial artery: This artery is continuous with the axillary artery at the inferior border of the teres major. It continues through the brachium to supply muscles of the anterior arm. This can be best observed on the deep dissection and plastinated tissue.
    • Deep brachial artery: This is the only branch of the brachial artery you are responsible for in this unit. It branches from the brachial artery in the mid-arm region and runs posteriorly. This is difficult to see in the cadaveric specimens.
  • Ulnar and radial arteries: The brachial artery divides into the radial and ulnar arteries in the cubital fossa. They run on the side of the antebrachium (forearm) of the bone with the same name. These are visible in the deep dissection, though the ulnar artery is cut in the forearm.
  • Superficial and deep palmar arches: The superficial palmar arch is visible in the plastinated tissue, and both are visible in images. These are formed from the ulnar and radial arteries.
  • Digital arteries: These branch from the superficial and deep palmar arches and travel to the sides of each digit.

Veins

The veins have been removed from the dissected cadaveric specimens. However, they are visible in images and on the plastinated specimens. There are two primary veins that originate in the forearm:

  • the cephalic and the basilic veins. The cephalic vein runs on the lateral aspect of the forearm and arm, while the basilic vein runs on the medial aspect of the forearm and arm.
  • In the cubital fossa, the median cubital vein join the basilica and cephalic veins. The median cubital vein is a common site for blood draws.
  • The brachial vein drains the muscles of the arm and then joins the basilic vein to become the axillary vein. The cephalic vein drains into the axillary vein, and then the axillary vein becomes the subclavian vein at the border of the first rib.

Activity 2: Anatomy TV-Upper Extremity Vasculature 

Your lab TA will login to the AnatomyTV computer resource. We will use this resource to explore the neurovasculature of the upper extremity.

  • Arteries of the Upper Extremity: Click on the tab marked Upper Body, you can also click on the upper limb tab and the views underneath it and be sure the red arteries circle is checked at the bottom of the window.
    • Explore the upper extremity arterial structure. To get the best view you will need to use the zoom and the mouse to slide the image into the best position. Look for the following:
      • Subclavian artery – visible
        • Thyrocervical trunk – visible
        • Suprascapular artery – not visible
      • Axillary artery – visible
        • Superior thoracic artery – not visible
        • Thoracoacromial artery – visible
        • Lateral thoracic artery – not visible
        • Anterior circumflex humeral artery – visible**
        • Posterior circumflex humeral artery – visible **
        • ***note Anatomy TV calls these collectively the circumflex humeral artery, we want you to know both***
        • Subscapular artery – visible
          • Thoracodorsal artery – not visible
          • Circumflex scapular artery – not visible
      • Brachial Artery – visible
        • Deep Brachial Artery – visible
        • Radial Artery – visible
        • Ulnar Artery – visible

Students should refer to the atlas and the video available during lab to identify the arteries listed above that are not visible in Anatomy TV. See the notes below on tips for identifying the arteries of the axilla and arm.

Highlight each of the structures outlined above and look at the box on the upper right hand side of the screen and review the information provided. Review as many of the visible vasculature structures as possible.

Work carefully through all the layers. Be sure to rotate the structure to appreciate multiple points of view. Notice at layer 11 how the artery travels behind the pectoralis major and the proximity of the subclavian and axillary artery in relation to the first rib and clavicle. The arterial structures are best visualized in layers 1-5. 

Here are a few tips for identifying arteries of the axilla and arm: 

  • The subclavian becomes the axillary artery at the lateral border of the first rib.
  • The axillary artery becomes the brachial artery at the inferior border of the teres major.
  • The axillary artery is divided into three parts by the pectoralis minor muscle, with the first part being medial to the muscle, the second part being deep to the muscle, and the third part being lateral to the muscle. The first part has one branch, the second part has two branches, and the third part has three branches.

Veins of the Upper Extremity: 

Click on the tab marked Upper Body, you can also click on the upper limb tab and the views underneath it and be sure the blue and green circle is checked at the bottom of the window.

Explore the upper extremity arterial structure. To get the best view you will need to use the zoom and the mouse to slide the image into the best position. Look for the following:

  • Cephalic vein – visible 
  • Basilic vein – visible
  • Median cubital vein – visible
  • Brachial vein – visible
  • Axillary vein – visible
  • Subclavian vein – visible (under the head and neck tab)

Highlight each of the structures outlined above and look at the box on the upper right hand side of the screen and review the information provided. Review as many of the visible vasculature structures as possible. 

Here are a few tips for identifying veins of the axilla and arm: 

  • Cephalic vein:  This passes superficially on the lateral side of the forearm, ascending lateral to the bicep and medial to the deltoid.
  • Median cubital vein: This is superficial ascending medially in the cubital fossa.
  • Basilic vein: This is superficial on the dorsum of the hand, ascending the medial aspect of the forearm, continuing up the arm where it travels medial and deep to the biceps.
  • Brachial vein: This ascends superficially on the medial side of the arm between the long head of the triceps and the biceps.
  • Axillary vein: This ascends medially through the axilla, it is a continuation of the brachial vein.
  • Subclavian vein: This is a continuation of the axillary vein as it passes over the first rib.

Activity 3:  Brachial Plexus Exercise (Card Placement + atlas)

This exercise is designed to help you learn the branches of the brachial plexus and the muscles that those branches innervate. The brachial plexus provides innervation to all muscles and skin of the upper extremity. These nerves originate from the C5-T1 roots. Then they branch and merge, creating a web of nerves at the trunk, division, and cord levels. Several branches off of the trunk and cord levels innervate muscles acting on the pectoral girdle. Finally, the branchial plexus ends as fiver terminal branches. The posterior cord splits into the axillary and radial nerves. Branches of both the medial and lateral cords merge to form the median nerve. The rest of the medial cord becomes the ulnar nerve, while the rest of the lateral cord becomes the musculocutaneous nerve. These terminal branches innervate the rest of the muscles of the upper extremity.

image

  • On the table you will see a poster with an unlabeled brachial plexus. You will also see labels for nerves (blue) and muscles (red). Using atlases and laminated images, first use the blue nerve labels to correctly label the branches of the brachial plexus. Then, using muscle charts, place the muscles next to the nerve that innervates them.
  • You should also be aware of the region of skin innervated by each terminal branch of the brachial plexus. Knowing both the muscles innervated by each branch and the region of skin innervated by the terminal branches has clinical relevance, as it can help you determine which nerve (or nerve root, as will be explained in lecture) may be damaged. The region of skin innervated by each terminal branch of the brachial plexus is shown in this figure:

image

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Human Anatomy Lab Manual by Julie Stamm, PhD, LAT, ATC and Patrick Hills-Meyer, EdD, LAT, ATC, CSCS is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.

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