Fascia, vessels and nerves of the upper limb
Definitions & Key takeaways
Fascia is a type of connective tissue that surrounds muscles, organs, and other structures in the body. It provides support and protection and helps to keep everything in its place. The upper limbs have superficial and deep fascia layers.
Superficial fascia is the closest layer to the skin, while deep fascia lies beneath it. The superficial fascia provides insulation, cushion and passageway of vessels and nerves and blood vessels, whereas the deep fascia envelopes and organizes muscles into compartments.
Introduction0:00–0:20
The upper limb contains an intricate metro system of blood vessels, muscles, and nerves. These structures are wrapped up and organized into different compartments by superficial and deep fascia layers, and together they form the multifunctional upper limbs we know and love.
So let’s start with the fascia. You can think of fascia as a pair of thin stockings made of connective tissue that support and bind together different parts of the body, including the lower limbs.
Fascia0:20–7:12
Now, each upper limb actually has two pairs of stockings on top of each other: the superficial fascia, which sits right underneath our skin, and the deep fascia, which is deep to or beneath the superficial fascia, and it sits on top of muscles, organizing them into compartments.
In the upper limb, there are six fasciae to remember. We have the pectoral fascia, the clavipectoral fascia, the axillary fascia, the deltoid fascia, the brachial fascia, and antebrachial fascia.
The wrist and the hand also have fibrous band-like structures called the flexor retinaculum, the extensor retinaculum, and the palmar aponeurosis.
OK, let’s start with the pectoral fascia, which is a broad thin sheath of connective tissue surrounding the pectoralis major muscle, from which it gets its name.
Medially, the pectoral fascia is attached to the sternum along with the pectoralis major’s origin. Superiorly, it attaches to the clavicle, and superolaterally, this fascia passes over this narrow trench called the deltopectoral groove to blend with the deltoid fascia covering the deltoid muscle around the shoulder.
The deltopectoral groove serves as a passageway for the cephalic vein when it is traversing from the arm to enter the lateral aspect of the chest.
Inferiorly, the pectoral fascia spreads downwards and becomes continuous with the fascia of the anterior abdominal wall, while on the lateral side, the fascia curves around the lateral border of the pectoralis major to become continuous with the axillary fascia in the floor of the axilla.
Next comes the clavipectoral fascia, which is deep to the pectoral fascia and pectoralis major. Superiorly, it is attached to the clavicle.
Immediately below the clavicle, the clavipectoral fascia encloses the subclavius muscle and then the pectoralis minor muscle before becoming continuous with the axillary fascia inferiorly.
Between the pectoralis minor and the subclavius, there’s the costocoracoid membrane, which is pierced by the lateral pectoral nerve innervating the pectoralis major, the cephalic vein, and the thoracoacromial artery.
Unsurprisingly, the fascia covering the deltoid muscle is called the deltoid fascia. Superiorly, the deltoid fascia attaches to the clavicle, the acromion process and the spine of the scapula.
It then spreads downwards to cover the superficial surface of the deltoid muscle. Inferiorly, it merges with the pectoral fascia on the anteromedial side, the infraspinous fascia posteriorly, and the fascia of the arm distally.
Alright, now let’s have a look at the fascia of the arm, also called the brachial fascia. The brachial fascia is a tough connective tissue looking like the sleeve of a t-shirt covering the muscles of the arm.
The anterior compartment is also called the flexor compartments because it houses muscles responsible for the elbow flexion, while the posterior compartment is called the extensor compartment because it houses muscles responsible for elbow extension.
At its distal part, the brachial fascia is continuous with the antebrachial fascia or just the fascia of the forearm. The antebrachial fascia surrounds the muscles of the forearm, which are divided into two compartments by an intermuscular septum and a band of fibrous connective tissue called the interosseous membrane.
It is called the interosseous membrane because it connects two bones together, the radius and the ulna. The two compartments of the forearm are the posterior compartment, also called the extensor-supinator compartment as it contains muscles that extend the wrist and supinate the forearm, and the anterior or flexor-pronator compartment, which contains muscles that flex the wrist and pronate the forearm.
Over the posterior side of the arm, the fascia becomes thicker as it reaches the distal radius and ulna, eventually transforming into a transverse band known as the extensor retinaculum, which holds the extensor tendons in position.
On the anterior side, the antebrachial fascia also forms another thick fibrous band continuous with the extensor retinaculum referred to as the palmar carpal ligament.
Distal and deeper to the palmar carpal ligament lies the flexor retinaculum, which is another fibrous band that extends between the anterior prominences of the outer carpal bones.
Medially, the flexor retinaculum attaches to the pisiform and the hook of the hamate, while on the lateral side it attaches to the tubercle of scaphoid and the crest of the trapezium.
Together, the flexor retinaculum and the anterior concave surface made by carpal bones, form an osseofibrous tunnel called the carpal tunnel, which serves as a passageway for a nerve called the median nerve and the flexor tendons of the forearm.
In the hand, the antebrachial fascia extends beyond the flexor and extensor retinacula and becomes the palmar fascia. As it enters the hand, the central part of the palmar fascia, called the palmar aponeurosis, is a thick, tendinous, and triangular structure that covers the central compartment of the palm.
Proximally, the apex of this palmar aponeurosis blends with the flexor retinaculum and the tendon of the palmaris longus muscle.
Moving distally, four longitudinal bands radiate distally from the apex of the palmar aponeurosis. At the bases of the fingers, they become continuous with the fibrous tendon sheaths of the digits.
The medial border of the palmar aponeurosis becomes continuous with the hypothenar fascia, the one that covers the hypothenar muscles.
On its lateral border, the palmar aponeurosis becomes continuous with the thenar fascia covering the thenar muscles. Alright!!
Quiz7:12–7:24
Now let’s pause for a minute and see if you can identify the six fasciae of the upper limb! And now let’s switch gears a little bit, and talk about the veins of the upper limb, which can also be superficial or deep veins.
Veins7:24–7:44
The superficial veins are those which can be found in the superficial fascia and are easily accessible, for example when you need to have a blood sample taken.Initially, the superficial veins of the upper limb start as small veins in the subcutaneous tissues from the dorsal venous network of the hand.
Superficial veins7:44–10:10
They converge into bigger venous networks as they progress proximally up along the wrists and the forearm, resulting in big superficial veins called the cephalic vein, the basilic vein, and the median antebrachial vein also known as the median vein of the forearm.
The cephalic vein arises in the converging network of small veins from the lateral aspect of the dorsal venous network. The cephalic vein then ascends on the lateral border of the wrist, and travels up the anterolateral surface of the forearm and arm and is often visible through the skin.
Anterior to the elbow, the cephalic vein communicates with the median cubital vein which passes obliquely across the cubital fossa to meet up with the basilic vein which drains the medial side of the upper limb.
The cephalic vein continues its course superiorly in the arm on the lateral side between the deltoid and pectoralis major muscles in the deltopectoral groove and then through the deltopectoral triangle, a triangular space bordered by the clavicle, the lateral border of pectoralis major muscle, and the medial border of the deltoid muscle.
At this level, the cephalic vein empties into the terminal part of the axillary vein after it pierces the costocoracoid membrane of the clavipectoral fascia.
Similar to the cephalic vein, the basilic vein ascends in the subcutaneous tissue from the medial end of the dorsal venous network along the medial side of the forearm and inferior part of the arm.
Then, it pierces the brachial fascia to pass deep near the junction of the middle and inferior thirds of the arm, running superiorly, parallel to the brachial artery, eventually merging with the deep veins accompanying the brachial artery to form the axillary vein.
The median antebrachial vein is highly variable, and it usually starts at the base of the dorsum of the thumb, and then ascends between the cephalic and the basilic veins territories at the anterior aspect of the forearm.
It then joins the basilic vein below the cubital fossa, but in a few individuals, it can divide into a median cephalic vein draining into the cephalic vein and a median basilic vein that drains in the basilic vein.
Makes sense, right? OK, now let’s have a look at the deep veins.
Deep veins10:10–11:14
Unlike the superficial veins, the deep veins are located deep to the muscles, and they commonly accompany major arteries, so they’re called the “venae comitantes”, which is Latin for accompanying veins.
Just like the superficial veins, the deep veins start as a tiny network but this time it’s deep in the hand. These tiny veins then form the superficial and deep palmar venous arches.
On the medial side, this network gives rise to the ulnar veins which ascends alongside the ulnar artery on the medial side of the forearm.
On the lateral side of the hand, the deep palmar venous arch gives rise to the radial veins, which climbs up the forearm alongside the radial artery.
Both the ulnar and the radial veins terminate in the cubital fossa where they join to form the big deep veins of the arm known as the brachial veins.
Travelling alongside the brachial artery, the brachial veins continue up the arm, where they join the basilic vein to form the axillary vein.
Alright, so before we continue, let’s have you take a small pause and try to identify the three big superficial veins and two deep veins of the upper limb.
Quiz11:14–11:29
Now, alongside the veins run the lymphatic vessels which are responsible for the lymphatic drainage of the upper limb. Their major function is to collect excess fluids in the extracellular space, and bring it back into the venous circulation.
Lymphatic vessels11:29–13:30
Just like the veins, lymphatic vessels are also divided into superficial and deep lymphatic vessels. The superficial lymphatic vessels of the upper limb also start as a network of tiny lymph vessels in the skin of the hand called the lymphatic plexuses, and they converge into bigger lymph vessels that ascend the upper limb mostly alongside the cephalic and basilic veins.
Some of the lymphatic vessels which travel alongside the basilic vein drain in the cubital lymph nodes. These lymph nodes are located medial to the basilic vein and proximal to the medial epicondyle of the humerus.
From the cubital lymph nodes arise other lymph vessels which ascend in the arm to terminate in the humeral or lateral axillary lymph nodes.
On the other hand, other lymphatic vessels on the lateral side of the forearm and the arm, run alongside the cephalic vein, to the proximal part of the arm.
At this level, they either cross medially to enter the apical axillary lymph nodes, or drain into the deltopectoral lymph nodes at the tip of the deltopectoral groove.
The deep lymphatic vessels are less numerous than the superficial lymphatic vessels. But just like the superficial lymphatic vessels, the deep lymphatic vessels also follow the course of the nearby deep veins such as the ulnar, radial and brachial veins, as they ascend to terminate in the humeral or lateral axillary lymph nodes.
Unlike the superficial veins which mainly drain fluids from the subcutaneous tissue, the deep lymphatic vessels drain lymphatic fluids from structures buried deep in the body, such as the bone periosteum, tendons, joint capsules, and muscles.
Okay, now let’s have a look at the cutaneous innervation of the upper limb. This consists of a network of nerves that carry sensations of pain, touch, temperature, and pressure to the central nervous system.
Cutaneous innervation13:30–18:19
They also carry some sympathetic fibers, which supply the sweat glands, small arteries in the skin, and arrector pili muscles.
Cutaneous nerves of the upper limb carry fibers originating from the spinal roots of the C3 to the T2 spinal segment. This spinal segment can be divided into three parts.
First one goes from C3 to C4, and it’s part of the cervical plexus, which normally extends from C1 to C4. The second goes from C5 to T1, and it forms the brachial plexus.
The last part consists of the T2 spinal segment, which gives rise to the lateral cutaneous branch of the second intercostal nerve, called the intercostobrachial nerve.
So every spinal segment receives sensory fibers from a specific territory of the skin, and these specific areas of skin are what we call dermatomes which we will discuss after we describe the cutaneous innervation of the upper limb.
Alright, now, let’s see how cutaneous innervation of the upper limb is distributed. The most proximal dermatomes are innervated by the cervical plexus, via the supraclavicular nerves originating in the C3 and C4 spinal segments.
The supraclavicular nerves innervate the skin at the base of the neck, and extend laterally over the shoulder. The lateral aspect of the arm gets its innervation from the superior lateral cutaneous nerve of the arm branching from the axillary nerve and the inferior lateral cutaneous nerve of the arm often branching from the radial nerve both originating from the C5 and C6 spinal segments.
The skin under the axilla and the upper part of the medial side of the arm, get their innervation from the intercostobrachial nerve, which is T2, while the skin immediately below this level, on the medial part of the arm gets its innervation from the medial cutaneous nerve of the arm which is mainly from T1.
The posterior aspect of the arm gets its innervation from the posterior cutaneous nerve of the arm, which is also a branch of the radial nerve and originates from the C5 to C8 spinal segments.
The skin over the lateral side of the forearm gets its innervation from… well, you’ve guessed it… the lateral cutaneous nerve of the forearm.
This nerve is a branch of the musculocutaneous nerve, and it originates its fibers from the C5 and C6 spinal segments. The skin over the posterior side of the forearm gets its innervation from the posterior cutaneous nerve of the forearm, the branch of the radial nerve, originating its fibers from the C5 to C8 spinal regions.
The medial side of the forearm is supplied by the medial cutaneous nerve of the forearm, which originates its fibers from the C8 and T1 spinal segment.
Initially, this nerve runs with the ulnar nerve before it perforates the deep fascia at approximately the mid-arm to enter the subcutaneous tissue of the forearm to innervate the skin over the medial side of the forearm.
Now, let’s have a look at the cutaneous innervation of the hand starting with the palm. The lateral two-thirds of the palm are innervated by the palmar cutaneous branch of the median nerve, which is C6 to C8.
Still, on the palm side, the medial one third gets its innervation from the palmar cutaneous branch of the ulnar nerve which is C8 and T1.
Turning the hand to look at its dorsal surface, the lateral two-thirds get their innervation from the superficial terminal branch of the radial nerve which is C6 to C8.
Still on the dorsum of the hand, the medial one-third of the dorsum of the hand gets its innervation from the dorsal cutaneous branch of the ulnar nerve.
OK, let’s now have a look at the digits. The palmar aspects of the lateral three and a half digits, plus their dorsal distal halves are innervated by the digital branches of the median nerve originating in the C6 to C8 spinal roots.
The palmar aspects of the medial one and a half digits, plus their dorsal distal halves get their innervation from the palmar digital branches of the ulnar nerve which is C8 and T1.
Flipping the hand, the dorsal aspects of the proximal parts of the lateral three and a half digits get their innervation from the digital branches of the radial nerve which is C6 to C8.
Lastly, the dorsal aspects of the proximal parts of the medial one and a half digits get their innervation from dorsal digital branches of the ulnar nerve.
Dermatomes18:19–19:33
OK now hold on, you might be thinking that this weird dermatomal arrangement of the upper limb, doesn’t seem to follow any pattern at all?
But it’s actually quite the opposite. They follow a well-defined and predictable pattern based on the embryonic origin of the upper limb.
To understand this, let’s hold the arms in the abducted position, with all the joints extended and the thumb facing upwards.
In this position, you can see that the dermatomes of the upper limb are arranged in a specific numerical sequence, where we start at the base of the neck, travel distally down the lateral or radial side of the arm, move across the digits laterally to medially, come back up the medial or ulnar side of the arm proximally and end in the axilla.
On the lateral side of the upper limb, from the shoulder to the thumb, the skin is innervated by fibers from the C3 to C6 spinal segments.
From the thumb to the little finger, it is by C6 to C8 spinal, and finally, on the medial side of the arm, from the little finger to the axilla it is by the C8 to T2 spinal segments.
Like many things in anatomy, this dermatome map can vary, however this is a general dermatomal pattern often used during clinical examination to test for cutaneous sensation.
Myotomes19:33–21:40
Switching to myotomes, these are defined as muscles that receive motor innervation from a single spinal nerve. Now, upper limb muscles usually receive motor fibers from more than one spinal cord segment or nerve, which, of course, complicates things and results in most muscles having more than one myotome.
To understand the concept of myotomes, it is easier to associate certain myotomes with different movements that occur in the upper limb, and then relate that to the muscle responsible for that movement.
For example, the myotomes for the movement of elbow flexion are both the C5 and C6 myotome. This makes sense because elbow flexion is carried out by the brachialis and biceps brachii muscles which are innervated by the musculocutaneous nerve.
Elbow flexion having the C5 and C6 myotome is derived from the fact that the musculocutaneous nerve originates from the C5 - C7 nerve roots, where the C5 and C6 portion is responsible for elbow flexion.
By knowing which muscles cause movements of the upper limb, we can figure out the myotomes of those movements, which ultimately can be tested clinically to help determine nerve dysfunction.
Let's take a closer look at the myotomes that govern the rest of the movements of the upper limb: Glenohumeral lateral rotation is myotome C5, and medial rotation are myotomes C6 - C8.
Glenohumeral abduction is C5, and adduction is C6-C8. Glenohumeral flexion is C5, and extension is C6 - C8.
Moving on to the elbow joint, elbow flexion is C5, C6, and elbow extension is C6, C7. Forearm supination is C6, and pronation is C7, C8.
At the wrist joint, both extension and flexion is C6, C7. Finally, at the hand, digit flexion and extension are C7, C8, where digit abduction and adduction are controlled by T1.
Quiz21:40–21:58
OK, here’s one last pause before we recap. Can you recall the cutaneous innervation of the upper limb from an anterior view?
Alright, as a quick recap. In the pectoral region, there’s the pectoral fascia which envelops the pectoralis major muscle, the clavipectoral fascia enveloping the subclavius and the pectoralis minor muscle, and the axillary fascia, which forms the dome of the armpit.
Review21:58–25:01
In the shoulder region, there’s the deltoid fascia which covers the deltoid muscle. Distally, there’s the brachial fascia which encloses the muscles of the arm and divides them into the anterior and posterior compartments by its intermuscular septa.
In the forearm, there’s the antebrachial fascia, which envelops the muscles of the forearm which are divided into an anterior and posterior compartment thanks to the intermuscular septum and the interosseous membrane.
The major superficial veins of the upper limb are the cephalic vein that drains the lateral side of the limb, the basilic vein that drains the medial side, and the median antebrachial vein which drains the middle anterior part of the forearm.
Regarding the deep veins, on the other hand, the ulnar and the radial veins drain into the brachial veins which ultimately drain into the axillary vein.
Now, regarding lymphatics. In the forearm, the lymphatic vessels drain into the cubital lymph nodes on the medial side of the forearm before continuing in the arm to terminate in the lateral axillary lymph nodes.
Laterally, the lymph vessels climb up to the proximal part of the arm, to either cross medially and enter the apical axillary lymph nodes, or, continue to ascend to terminate in the deltopectoral lymph nodes.
Finally, the cutaneous innervation of the upper limb comes from spinal roots C3 to T2, and derives from the cervical plexus, the brachial plexus and the T2 spinal segment.
Regarding the dermatomes, on the lateral side of the upper limb, from the shoulder to the thumb, the skin is innervated by fibers from the C3 to C6 spinal segments.
From the thumb to the little finger, it is by C6 to C8 spinal, and finally, on the medial side of the arm, from the little finger to the axilla it is by the C8 to T2 spinal segments.
Regarding the myotomes, glenohumeral lateral rotation is myotome C5, and medial rotation is C6 to C8. Glenohumeral abduction is C5, and adduction is C6 to C8.
Glenohumeral flexion is C5, and extension is C6 to C8. Moving on to the elbow joint, elbow flexion is C5, C6, and elbow extension is C6, C7.
Forearm supination is C6, and pronation is C7, C8. At the wrist joint, both extension and flexion is C6, C7.
Finally, at the hand, digit flexion and extension are C7, C8, where digit abduction and adduction are controlled by T1.
- "Human Anatomy & Physiology, 11th edition" Pearson (2018)
- "Costanzo Physiology, 7th edition" Elsevier (2021)
- "Moore’s Clinically Oriented Anatomy, 9th edition" Wolters Kluwer (2023)
- "Peripheral nerve compression syndromes of the upper limb" Surgery (Oxford) (2022)
- "Clinical anatomy of the nerve supply to the upper limb" BJA Educ (2021)
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