Brachial Plexus
What clinical symptoms would a patient present with if this part was damaged?
Click to Start...
How many nerve roots contribute to this nerve?
If you encounter any difficulties while exploring this resource, please email
a.e.stephen@keele.ac.uk
Before exploring this resource further, consider how your prior anatomical learning links to the following 5 aspects of the brachial plexus...
Here is a link to an anonymous form to help gauge your current level of understanding regarding brachial plexus anatomy before working through this supplementary resource:
Please note this short form is entirely voluntary and anonymous!
Intended Learning Outcomes
Click the icons to reveal what content will be included in this resource
Define the 5 nerve roots that contribute to the brachial plexus
Draw the pathway of motor axons from each nerve root and differentiate the trunks, divisions and cords of the plexus
Compare the muscle groups that are innervated by each nerve branch of the brachial plexus
Attribute motor or sensory symptoms to common mechanisms of injury to the respective parts of the brachial plexus
Apply knowledge of close anatomical landmarks by linking features of the brachial plexus to clinical presentations
Brachial Plexus Anatomy HOMEPAGE
3. Functions
5. Practice questions
1. Introduction of components
Click here to go directly to the section that summarises the motor and sensory innervation for each nerve.
Click here to go directly to an overview section outlining the key features of the brachial plexus
Click here to go directly to practice questions and additional resources section
4. Application of knowledge
2. Drawing the brachial plexus
4. Clinical application
Practice questions
Click here to go directly to the section that summaries 8 steps on how to draw the brachial plexus
Click here to go directly to the section for a few pathological presentations.
What is the brachial plexus?
Start discovering by clicking to the next page...
Home
Mnemonic
Overview of components
Roots
Anterior rami of mixed spinal nerves
Trunks
Travel between the anterior and middle scalene muscles
The brachial plexus is a network of axons that originate from the spinal cord in the neck region and innervate the upper limb. As the nerves course from medial to lateral, the brachial plexus can be described as having the following parts...
Divisions
Pass either in front or behind the subclavian artery
Cords
One cord is behind the axillary artery and the other two are medial or lateral
Branches
Acland's Video ATLAS:
Summary of the brachial plexus
Although there are 5 main terminal branches, various nerves emerge to innervate the upper limb.
Home
Roots
VIDEO
Click to reveal the 5 contributions from the anter rami emerging from the spinal cord:
C5
C6
C7
C8
T1
Home
Trunks
Click to reveal the relationship of how the roots coalese to form the following 3 trunks:
Roots become trunks
Superior trunk
Middle trunk
Inferior trunk
Home
Subclavian arteries:
- Originate from either the brachiocephalic trunk on the right side or arch of aorta on the left side
- Travel through the interscalene triangle
- End at the lateral border of the 1st rib to become the axillary artery
Divisions
The subclavian artery is an important structure in relation to how the trunks divide. Click below to reveal how each of the trunks divide into 2 and travel in relation to the subclavian artery:
Anterior
Posterior
Home
Axillary artery:
- Originates from the subclavian as it crosses the lateral border of the first rib
- Divided into 3 parts in relation to pectoralis minor muscle
- Ends at the inferior border of teres major muscle to become the brachial artery
Cords
Click to reveal how the anterior and posterior divisions contribute to form 3 cords around the axillary artery:
Lateral cord
Posterior cord
Medial cord
Home
Branches
VIDEO
As an introduction to the names of the individual nerves branching from the brachial plexus, click the respective icons on the image to learn a contextual overview as to how the branches can be categorised into:
Supraclavicular branches = 4
Infraclavicular branches = 7
Terminal branches = 5
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Drawing the brachial plexus
Follow the steps to break the brachial plexus into more managable chunks
Home
Orientation
Step 1:
The first step is to decide whether the drawing will be for the right or left upper limb. Orientation grids are always useful when it comes to anatomical structures as this context can reduce the risk of getting lost or confused. In the worked example, we will focus on drawing the patient's left brachial plexus...
Superior
Inferior
Medial
Lateral
Left
Home
Draw the roots
Step 2:
The brachial plexus arises from a cervical enlargement of the spinal cord that is protected within the vertebral canal.
The brachial plexus emerges from an enlarged cervical region of the spinal cord that is protected within the vertebral canal.
Left
C1 (vertebra)
C2
C3
C4
C5
C6
C7
T1
First rib
C5
The anterior rami of 5 spinal nerves (C5-T1) emerge laterally through intervertebral foramina before entering the posterior triangle (click here) of the neck.
C6
C7
C8
Tip: Click the boxes to reveal the pattern of how the 5 roots are beginning to form 3 bundles...
T1
Home
Draw the trunks
Step 3:
The trunks of the brachial plexus are located superior to the clavicle. Click the icons to reveal how the 3 trunks are named according to their orientation in anatomical position.
Left
Superior
Middle
Inferior
Clavicle
Each trunk is a simple continuation from the respective roots:
1 = C5 + C62 = C73 = C8 + T1
Home
Draw the divisions
Step 4:
Click each trunk to see how it splits into 2 divisions, with one of these contributions passing deep underneath the subclavian artery.
Left
The easiest way to remember the pattern of how the 3 posterior divisions coalese behind the artery, is to start drawing the continuation from the middle trunk (click here) and join dotted lines from above and below.
The anterior division of the middle trunk has to pick a side of the artery, so crosses up to join superiorly.
Anterior
Posterior
vs.
Home
Draw the cords
The respective divisions of the brachial plexus descend distally into the axilla, which is lateral to the first rib.
Step 5:
Left
In terms of anatomical position, click the blue icons to see how the 3 cords now gather around the axillary artery and are named accordingly:
Lateral
Posterior
Medial
Home
Terminal branches
The three cords terminate by branching out into 5 main nerves that innervate the key compartments of the upper extremity.
Step 6a:
Left
The 3 terminal branches ANTERIOR to the axillary artery (click here) arise from either the lateral or medial cords and often create a characteristic 'm' shape:
Home
Terminal branches
The three cords terminate by branching out into 5 main nerves that innervate the key compartments of the upper extremity.
Step 6b:
Left
The 2 terminal branches POSTERIOR to the axillary artery (click here) only originate from the posterior cord and travel deeply.
Home
There are a total of 4 supraclavicular nerves that emerge from the proximal and most superior parts of the brachial plexus. Click each icon to reveal the name and tip to identify each branch.
Step 7:
Supraclavicular branches
Left
Home
Note that no branches typically arise from the DIVISIONS, meaning this part can demarcate a classification based on nerves that emerge from the brachial plexus above or below the clavicle!
Step 8:
Infraclavicular branches
Divisions create a divide
Left
Lateral pectoral nerve
Excluding the terminal branches already described, there are a total of 7 infraclavicular nerves that emerge from the cords.
Start by drawing 3 subscapular nerves dropping down from the POSTERIOR cord.
Lower subscapular nerve
Upper subscapular nerve
There are also 3 nerves that emerge from the MEDIAL cord.
Medial cutaneous nerve of FOREARM
The LATERAL cord only has one nerve, which travels to pectoralis major.
Medial cutaneous nerve of ARM
Medial pectoral nerve
Home
Middle subscapular nerve (thoracodorsal)
One final step that could be included, is to review and check your understanding of the various components. Before attempting to draw the brachial plexus on the following page, use the checklist below and click on the interactive elements to help you correctly identifying each feature on this example.
Review...
C5
C6
C7
Checklist tips:
C8
T1
Home
Can you draw the brachial plexus?
Click the paint tool in the top right corner to draw the respective parts of the brachial plexus. Try to have fun by creating your own colour-coding and add as much detail from memory, but feel free to use the homepage button if you would like to retrace the steps by repeating previous sections.
VIDEO
Home
When learning new material, it is often challenging to step back and look for "patterns" to help scaffold. To conclude this section, click the icons to reveal the 5 rules of 5...
Rule of 5's...
Did you spot any other patterns?
Home
What are the functions of the brachial plexus?
Let's add functional context to what each branch of the brachial plexus innervates...
Home
Posterior rami
- Supply motor innervation to deep muscles of the back
- Carry sensory info from a small area of skin overlying the spine
Motor vs. Sensory neurons:
To reach the roots of the brachial plexus, all motor signals travel through the ventral roots of spinal nerves to exit the spinal cord:
Anterior rami
- Supply motor innervation to majority of muscles in the body
- Carry sensory info from most parts of the body
The word 'ramus' means branch so consider each mixed spinal nerve being like the trunk of a tree with it's roots protected inside the vertebral canal
Sensory axons carry signals from the spinal nerves and enter the spinal cord using the dorsal roots. It is important to differentiate the terminology as the roots of the brachial plexus are actually anterior rami of 'mixed' spinal nerves carrying both types of signal!
Click for summary
Home
INNERVATION
A mixed spinal nerve can carry both motor (efferent) and sensory (afferent) neurons. To understand the destination of where the neural signals are heading, this section has been divided by grouping each nerve of the brachial plexus into the following 3 parts:
Distal branches
Proximal branches
Terminal branches
Let's start by exploring the functions of the 5 main brachial plexus nerves...
Click for a (silly) Mnemonic
Home
Musculocutanous nerve
Click the icons to reveal how neural signals travel through the brachial plexus to form musculocutaneus nerve...
C6
C5
C7
C5
C8
T1
C6
C5, C6 and C7
C7
Lateral cord
C8
Click action for additional info
T1
Flexes forearm at elbow
Skin of lateral forearm
Acland's Video:
See biceps brachii, coracobrachialis + brachialis
Home
Axillary nerve
Click the icons to reveal how neural signals travel through the brachial plexus to form axillary nerve...
C6
C5
C5
C7
C8
T1
C6
C5 and C6
C7
Posterior cord
C8
Click action for additional info
T1
Abducts arm at shoulder
Skin of upper lateral arm
Acland's Video:
See deltoid + teres minor
Home
Median nerve
Click the icons to reveal how neural signals travel through the brachial plexus to form median nerve...
C6
C5
C7
C8
T1
C5
C6
(C5) C6, C7, C8 and T1
C7
Medial + lateral cords
C8
Click action for additional info
Majority of muscles in the anterior forearm
T1
Lateral palm and digits 1-3
Acland's Video:
See the median nerve in the forearm and hand
Median n.erve is located in the centre and forms the middle of the 'm' shape anterior to the axillary artery.
Home
Radial nerve
Click the icons to reveal how neural signals travel through the brachial plexus to form radial nerve...
C6
C5
C7
C8
T1
C5
C6
C5, C6, C7, C8 and T1
C7
Posterior cord
C8
Click action for additional info
Posterior muscles of the arm & forearm
T1
Posterior arm, forearm and lateral dorsal hand
Acland's Video:
See triceps brachii, anconeus + brachioradialis
Acland's Video:
See the radial nerve in the forearm and hand
Home
Ulnar nerve
Click the icons to reveal how neural signals travel through the brachial plexus to form ulnar nerve...
C8
T1
C6
C7
C5
C5
C6
C8 and T1
C7
Medial cord
C8
Click action for additional info
T1
Deep muscles of the hand
Medial hand (palm+dorsum) and digits 4+5
Acland's Video:
See the ulnar nerve in the forearm and hand
Home
INNERVATION
The next part of this section will focus on the branches of the brachial plexus that are associated with the roots and trunks:
Distal branches
Proximal branches
Terminal branches
There are 4 nerves that arise superior to the clavicle...
Home
Dorsal scapular nerve
Click the icons to reveal how neural signals travel through the brachial plexus to form dorsal scapular nerve...
C6
C7
C8
T1
Rhomboid MINOR
Rhomboid MAJOR
C5
Roots
C6
(C4) C5
C7
C8
Click action for additional info
T1
Retraction + elevation of scapula
No
Acland's Video:
See rhomboid major + minor
Home
Suprascapular nerve
Click the icons to reveal how neural signals travel through the brachial plexus to form suprascapular nerve...
C5
C7
C8
T1
Superior trunk
C6
C5 and C6
C7
Anterior view
Posterior view
Suprascapular nerve
Supraspinatus m.
Infraspinatus m.
C8
Click action for additional info
T1
Lateral rotation + first 15° of abduction at shoulder
No
Acland's Video:
See supraspinatus + infraspinatus
Home
Nerve to subclavius
Click the icons to reveal how neural signals travel through the brachial plexus to form nerve to subclavius...
C5
C7
C8
T1
Superior trunk
C6
C5 and C6
C7
Subclavius muscle
Nerve branching from superior trunk
C8
Click action for additional info
T1
Stabilizes & anchors clavicle to 1st rib
No
Acland's Video:
See subclavius
Home
Long thoracic nerve
Click the icons to reveal how neural signals travel through the brachial plexus to form long thoracic nerve...
C5
Roots
C8
T1
Serratus anterior m.
C6
C5, C6 and C7
C7
C8
Click action for additional info
T1
Protracts + anchors scapula against thorax
No
Acland's Video:
See serratus anterior
Home
INNERVATION
The next part of this section will focus on the branches of the brachial plexus that are associated with the cords:
Distal branches
Distal branches
Proximal branches
Terminal branches
With the exception of the terminal branches, there are 7 nerves inferior to the clavicle...
Home
Upper subscapular nerve
Click the icons to reveal how neural signals travel through the brachial plexus to form upper subscapular nerve...
C5
C7
C8
T1
C6
C5 (C6)
C7
Posterior cord
C8
Click action for additional info
T1
Medially rotates arm
No
Acland's Video:
See subscapularis
Home
Lower subscapular nerve
Click the icons to reveal how neural signals travel through the brachial plexus to form lower subscapular nerve...
C5
C7
C8
T1
C6
(C5) C6
C7
Posterior cord
C8
Click action for additional info
T1
Medially rotates arm
No
Acland's Video:
See subscapularis + teres major
Home
Thoracodorsal nerve
Click the icons to reveal how neural signals travel through the brachial plexus to form middle subscapular nerve...
C5
T1
C5
C6
C6, C7 and C8
C7
Posterior cord
C8
Click action for additional info
T1
- Extends arm
- Adducts arm
- Medially rotates arm
No
Acland's Video:
See latissimus dorsi
Home
Lateral pectoral nerve
Click the icons to reveal how neural signals travel through the brachial plexus to form lateral pectoral nerve...
C5
C8
T1
C6
C5, C6 and C7
C7
Lateral cord
C8
Click action for additional info
T1
- Flexes arm
- Adducts arm
- Medially rotates arm
No
Acland's Video:
See pectoralis major
Home
Medial pectoral nerve
Click the icons to reveal how neural signals travel through the brachial plexus to form medial pectoral nerve...
C6
C7
C5
C5
C6
C8 and T1
C7
Medial cord
C8
Click action for additional info
T1
Protracts scapula
No
Acland's Video:
See pectoralis major + minor
Home
Medial cutaneous nerves
Click the icons to reveal how neural signals travel through the brachial plexus to form medial cutaneous nerves...
C5
C6
C7
C5
C6
C7
C5
C6
C8 and T1
C7
Medial cord
C8
T1
No
- Skin of distal medial arm
- Skin of medial forearm
Home
Review...
To conclude this section, click the paint tool in the top right corner and draw how nerve signals travel through the various parts of the brachial plexus. Click the icons (numbers) on the template for helpful prompts. Understanding where and how the axons typically travel is an important step before attempting the next section.
Superior
Inferior
Lateral
Medial
- Musculocutaneous = C5, C6 and C7
- Axillary = C5 and C6
- Median = (C5) C6, C7, C8 and T1
- Radial = C5, C6, C7, C8 and T1
- Ulnar = C8 and T1
- Dorsal scapular = (C4) C5
- Suprascapular = C5 and C6
- Nerve to subclavius = C5 and C6
- Long thoracic = C5, C6 and C7
- Lateral pectoral = C5, C6 and C7
- Upper subscapular = C5 (C6)
- Lower subscapular = (C5) C6
- Thoracodorsal (middle subscapular) = C6, C7 and C8
- Medial pectoral = C8 and T1
- Medial cutaneous nerve of arm = C8 and T1
- Medial cutaneous nerve of forearm = C8 and T1
Home
Clinical Application
After considering the nerves individually, hopefully you noticed there is a degree of overlap in terms of different muscles acting across the various joints. Let's apply some clinical context by working through a few examples of how different types of injury can present in a patient...
Home
Dermatome
Myotome
Myotome:
- A group of spinal roots that collectively innervate a group of muscles
- Asking a patient to perform an action against resistance can assess assymmetry, pain or weakness.
- Tendon reflex hammers can test the integrity of sensory/motor reflex arcs at known spinal levels
Dermatome:
- Area of skin innervated by a single nerve root
- Cotton wool (light touch) can test the integrity of the dorsal column pathway at known spinal levels
- Pin-prick (pain) can test the spinothalamic tract at known spinal levels
In the previous section, specific names (e.g. medial cutaneous n. of the forearm) were given to nerves carrying sensation from the skin.
To be as efficient as possible in a clinical setting, it is important to consider the biomechanical context of muscles working together rather than acting independently.
The stripey organisational pattern is quick to figure out with key landmarks and very easy to measure:
One way to simplify the approach is to focus on primary muscle actions that correlate with specific root levels, for example:
C5 = Sunrise
- Abduction of arm
- DELTOID muscle
- Innervated by axillary nerve
- C5...think sunrise!
C5
T1
C6
C8
C7
Home
Clinical Examination
In previous sections, we outlined the motor and sensory distribution of each nerve. When considering how to test the various elements, the American Spinal Injury Association (ASIA) form can be a helpful tool. Watch the video below to see how all of this information can be applied to screen for brachial plexus injuries:
Myotome:
- A group of spinal roots that collectively innervate a group of muscles
Dermatome:
- Area of skin innervated by a single nerve root
Home
Clinical presentations:
"Klumpke palsy"
"Erb-Duchenne palsy"
= upper trunk injury!
= lower trunk injury!
C5
C5
- Any nerve that branches distal to the inferior trunk will not recieve C8 or T1 signals, as indicated by the dotted lines.
- Any nerve that branches distal to the superior trunk will not recieve C5 or C6 signals, as indicated by the dotted lines.
C6
C6
C7
C7
C8
C8
- Click icons to check if signals from other nerve roots will still allow 'weak' movements?
T1
T1
Home
Clinical presentation:
If damage occurs to a single nerve branch, the functional deficits will be less extensive and typically affect one group of muscles. When approaching problem based cases, it could be helpful to consider the following questions:
C5
"Winged scapula"
C6
C7
C8
T1
"C5-6-7... wings of heaven"
- What structure is injured?
- Does it carry motor innervation...how would you test the muscle action?
- Does it carry sensory innervation...where would you test for numbness?
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Quick Clinical Overview
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Practice Questions
Spaced repetition is a great way to consolidate learning...
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Microsoft Quiz
Now you have worked through the content of this supplementary media, if you would like to complete the anonymous form here will be a selection of questions as well as an opportunity to record feedback on your experience.
Please note the form and practice questions are entirely voluntary, automatically anonymised and free to repeat as many times as you would like!
Mnemonic
Home
Additional Resources
Blank template
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Axillary nerve travelling below surgical neck of humerus
Subscapularis muscle
The subscapularis muscle recieves dual innervation, meaning more than one nerve carries motor signals to initiate contraction:
Radial nerve travelling behind shaft of humerus
Upper subscapular nerve
Lower subscapular nerve
Because the muscle fibres insert anteriorly on the lesser tuberosity, this results in INTERNAL (or medial) rotation of the humeral head in the glenoid fossa.
Muscles of the HYPOTHENAR eminence
Couple of medial muscles in the ANTERIOR forearm
= Flexion of metacarpophalageal joints (digits 4+5)
Lumbricals (1/2)
Ulnar canal (of Guyon)
Opponens digiti minimi
= Opposition of digit 5
Abductor digiti minimi brevis
Flexor digiti minimi brevis
Other hand muscles
Adductor pollicis
Flexor carpi ulnaris
= Flexion + adduction of hand at wrist
Palmaris brevis
Palmar interossei
Flexor digitorum profundus (1/2)
= Flexion of distal IP joints (digits 4+5)
Dorsal interossei
Muscles of the THENAR eminence
Most muscles in the ANTERIOR forearm
Pronator teres
Flexor carpi radialis
= Flexion + abduction of hand at wrist
Carpal tunnel
Palmaris longus
= Flexion of hand at wrist
Opponens policis
= Opposition of digit 1
= Flexion of proximal IP joints (digits 2,3,4+5)
Flexor digitorum superficialis
Flexor digitorum profundus (1/2)
= Flexion of distal IP joints (digits 2+3)
Abductor policis brevis
= Flexion of thumb (digit 1)
Flexor pollicis longus
Flexor policis brevis
= Flexion of metacarpophalageal joints (digits 2+3)
Lumbricals (1/2)
Pronator quadratus
Deltoid muscle
Pectoralis major muscle
The lateral pectoral nerve only innervates one muscle: pectoralis major! Pectoralis major is considered to have 2 heads, therefore think of them needing both medial and lateral pectoral nerves for innervation:
Clavicular head
Sternocostal head
Mnemonic:
Organisation of the brachial plexus
Roots
Cords
Trunks
RootsTrunksDivisonsCordsBranches
Divisions
- Rugby =
- Teams =
- Drink =
- Cold =
- Beer =
Branches
POSTERIOR terminal branches
The RADIAL nerve is the largest of the terminal branches to supply the upper limb and has a close relationship with the shaft of the humerus:
Axillary n.
Radial n.
Middle subscapular nerve
MIDDLE subscapular nerve can also be called thoracodorsal
The thoracodorsal nerve also goes by the name MIDDLE subscapular because it is sandwiched between the upper and lower, however, it only innervates one muscle:
Latissimus dorsi
The tendon of latissimus dorsi muscle is closely associated with teres major muscle and can be seen twisting to insert to the medial lip of the intertubercular sulcus; thus resulting in INTERNAL (or medial) rotation.
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Conceptual Overview
Sensory neurons:
Motor neurons:
Muscle
Skin
- Start in the peripheral nervous system (PNS)
- Supplies skin which can sense - e.g. touch, pain, temperature, proprioception
- Also called afferent & ACCESS spinal cord
- Only travel through dorsal roots from the spinal nerve...think dorsal root ganglia
- Start in the central nervous system (CNS)
- Target muscles which contract and move
- Also called efferent & EXIT spinal cord
- Only travel through the ventral roots to reach a spinal nerve...think of driving a "motor/engine" car forwards
CNS
Efferent ->
<- Afferent
Superficial posterior forearm
POSTERIOR arm
Extensor carpi radialis longus
Anconeus
= Abduction of ulna when pronated
Extensor carpi radialis brevis
Extensor digitorum
Brachioradialis
= Accessory FLEXOR of forearm when mid-pronated
Extensor digiti minimi
Extensor carpi ulnaris
Deep posterior forearm
Supinator
Extensor indicis
Triceps brachii
- Long head = Extend + adduct arm at shoulder & extend forearm
- Medial head = Extend forearm at elbow
- Lateral head = Extend forearm at elbow
Extensor pollicis longus
Extensor pollicis brevis
Abductor pollicis longus
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ANTERIOR terminal branches
Musculocutaneous n.
Ulnar n.
Median n.
The characteristic 'm' shape is created when the lateral and medial cords combine to form the MEDIAN nerve located in the 'middle':
Superior
Orientation
Medial
Lateral
Inferior
This image shows the anterior view of the right brachial plexus and starts to provide anatomical context for applying knowledge to the opposite side. The divisions of the brachial plexus are typically located behind the clavicle and help classify supraclavicular versus infraclavicular branches.
Clavicle
NOTE: As the plexus travels laterally, it can also be described as coursing from proximal to distal.
ANTERIOR muscular compartment of the arm
Pierces coracobrachialis muscle
Musculocutaneous n. is the most lateral of the 3 branches helping to form an 'm' shape anterior to the axillary artery.
MOTOR innervation is supplied to the following muscles:
Becomes lateral cutaneous of forearm
Coracobrachialis
= Flexion of arm at shoulder
- Flexion of forearm at elbow
- Supinator
- Assists flexion of arm at shoulder
Biceps brachii
Brachialis
= Flexion of forearm at elbow
Mnemonic:
C6
C5
C7
Nerve roots for the 5 main branches
Musculocutaneous
C6
C5
Axillary
(4 or)
C6
C5
C7
C8
T1
Median
C6
C5
C7
C8
T1
Radial
C8
T1
Ulnar
Long head of biceps brachii tendon forms the intertubercular sulcus
Pectoralis minor muscle
The medial pectoral nerve branches from the medial cord of the brachial plexus close to the ribcage, and typically pierces through the middle of pectoralis minor muscle before also innervating major!
Pectoralis major
Pectoralis minor
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Key:
- Anterior scalene m.
- Middle scalene m.
- Posterior scalene m.
Posterior triangle of the neck
The roots of the brachial plexus can be found accompaning the subclavian artery as they travel between the anterior and middle scalene muscles - a space also known as the interscalene triangle.
Roots
(and trunks)
Subclavian v.
Rib 1
Quadrangular space
Deltoid muscle is triangular in shape with 3 parts
Axillary n. travels posteriorly around the surgical neck of the humerus and is closely associated with the posterior circumflex humeral branch of the axillary artery.
Axillary nerve supplies MOTOR innervation to:
Deltoid
- Abductor of arm at shoulder
- Assists flexion of arm
- Assists extension of arm
Teres minor
= Lateral rotation of arm at shoulder
Axillary nerve emerges posteriroly through the quadrangular space
UPPER subscapular nerve
Lower subscapular nerve
The subscapularis muscle recieves dual innervation, meaning more than one nerve carries motor signals to initiate contraction:
LOWER subscapular nerve
Subscapularis muscle
Teres major muscle
Because the muscle fibres insert anteriorly on the lesser tuberosity, this results in INTERNAL (or medial) rotation of the humeral head in the glenoid fossa.
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Brachial Plexus
Ash Stephen
Created on March 19, 2024
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Transcript
Brachial Plexus
What clinical symptoms would a patient present with if this part was damaged?
Click to Start...
How many nerve roots contribute to this nerve?
If you encounter any difficulties while exploring this resource, please email
a.e.stephen@keele.ac.uk
Before exploring this resource further, consider how your prior anatomical learning links to the following 5 aspects of the brachial plexus...
Here is a link to an anonymous form to help gauge your current level of understanding regarding brachial plexus anatomy before working through this supplementary resource:
Please note this short form is entirely voluntary and anonymous!
Intended Learning Outcomes
Click the icons to reveal what content will be included in this resource
Define the 5 nerve roots that contribute to the brachial plexus
Draw the pathway of motor axons from each nerve root and differentiate the trunks, divisions and cords of the plexus
Compare the muscle groups that are innervated by each nerve branch of the brachial plexus
Attribute motor or sensory symptoms to common mechanisms of injury to the respective parts of the brachial plexus
Apply knowledge of close anatomical landmarks by linking features of the brachial plexus to clinical presentations
Brachial Plexus Anatomy HOMEPAGE
3. Functions
5. Practice questions
1. Introduction of components
Click here to go directly to the section that summarises the motor and sensory innervation for each nerve.
Click here to go directly to an overview section outlining the key features of the brachial plexus
Click here to go directly to practice questions and additional resources section
4. Application of knowledge
2. Drawing the brachial plexus
4. Clinical application
Practice questions
Click here to go directly to the section that summaries 8 steps on how to draw the brachial plexus
Click here to go directly to the section for a few pathological presentations.
What is the brachial plexus?
Start discovering by clicking to the next page...
Home
Mnemonic
Overview of components
Roots
Anterior rami of mixed spinal nerves
Trunks
Travel between the anterior and middle scalene muscles
The brachial plexus is a network of axons that originate from the spinal cord in the neck region and innervate the upper limb. As the nerves course from medial to lateral, the brachial plexus can be described as having the following parts...
Divisions
Pass either in front or behind the subclavian artery
Cords
One cord is behind the axillary artery and the other two are medial or lateral
Branches
Acland's Video ATLAS:
Summary of the brachial plexus
Although there are 5 main terminal branches, various nerves emerge to innervate the upper limb.
Home
Roots
VIDEO
Click to reveal the 5 contributions from the anter rami emerging from the spinal cord:
C5
C6
C7
C8
T1
Home
Trunks
Click to reveal the relationship of how the roots coalese to form the following 3 trunks:
Roots become trunks
Superior trunk
Middle trunk
Inferior trunk
Home
Subclavian arteries:
Divisions
The subclavian artery is an important structure in relation to how the trunks divide. Click below to reveal how each of the trunks divide into 2 and travel in relation to the subclavian artery:
Anterior
Posterior
Home
Axillary artery:
Cords
Click to reveal how the anterior and posterior divisions contribute to form 3 cords around the axillary artery:
Lateral cord
Posterior cord
Medial cord
Home
Branches
VIDEO
As an introduction to the names of the individual nerves branching from the brachial plexus, click the respective icons on the image to learn a contextual overview as to how the branches can be categorised into:
Supraclavicular branches = 4
Infraclavicular branches = 7
Terminal branches = 5
Home
Drawing the brachial plexus
Follow the steps to break the brachial plexus into more managable chunks
Home
Orientation
Step 1:
The first step is to decide whether the drawing will be for the right or left upper limb. Orientation grids are always useful when it comes to anatomical structures as this context can reduce the risk of getting lost or confused. In the worked example, we will focus on drawing the patient's left brachial plexus...
Superior
Inferior
Medial
Lateral
Left
Home
Draw the roots
Step 2:
The brachial plexus arises from a cervical enlargement of the spinal cord that is protected within the vertebral canal.
The brachial plexus emerges from an enlarged cervical region of the spinal cord that is protected within the vertebral canal.
Left
C1 (vertebra)
C2
C3
C4
C5
C6
C7
T1
First rib
C5
The anterior rami of 5 spinal nerves (C5-T1) emerge laterally through intervertebral foramina before entering the posterior triangle (click here) of the neck.
C6
C7
C8
Tip: Click the boxes to reveal the pattern of how the 5 roots are beginning to form 3 bundles...
T1
Home
Draw the trunks
Step 3:
The trunks of the brachial plexus are located superior to the clavicle. Click the icons to reveal how the 3 trunks are named according to their orientation in anatomical position.
Left
Superior
Middle
Inferior
Clavicle
Each trunk is a simple continuation from the respective roots:
1 = C5 + C62 = C73 = C8 + T1
Home
Draw the divisions
Step 4:
Click each trunk to see how it splits into 2 divisions, with one of these contributions passing deep underneath the subclavian artery.
Left
The easiest way to remember the pattern of how the 3 posterior divisions coalese behind the artery, is to start drawing the continuation from the middle trunk (click here) and join dotted lines from above and below.
The anterior division of the middle trunk has to pick a side of the artery, so crosses up to join superiorly.
Anterior
Posterior
vs.
Home
Draw the cords
The respective divisions of the brachial plexus descend distally into the axilla, which is lateral to the first rib.
Step 5:
Left
In terms of anatomical position, click the blue icons to see how the 3 cords now gather around the axillary artery and are named accordingly:
Lateral
Posterior
Medial
Home
Terminal branches
The three cords terminate by branching out into 5 main nerves that innervate the key compartments of the upper extremity.
Step 6a:
Left
The 3 terminal branches ANTERIOR to the axillary artery (click here) arise from either the lateral or medial cords and often create a characteristic 'm' shape:
Home
Terminal branches
The three cords terminate by branching out into 5 main nerves that innervate the key compartments of the upper extremity.
Step 6b:
Left
The 2 terminal branches POSTERIOR to the axillary artery (click here) only originate from the posterior cord and travel deeply.
Home
There are a total of 4 supraclavicular nerves that emerge from the proximal and most superior parts of the brachial plexus. Click each icon to reveal the name and tip to identify each branch.
Step 7:
Supraclavicular branches
Left
Home
Note that no branches typically arise from the DIVISIONS, meaning this part can demarcate a classification based on nerves that emerge from the brachial plexus above or below the clavicle!
Step 8:
Infraclavicular branches
Divisions create a divide
Left
Lateral pectoral nerve
Excluding the terminal branches already described, there are a total of 7 infraclavicular nerves that emerge from the cords.
Start by drawing 3 subscapular nerves dropping down from the POSTERIOR cord.
Lower subscapular nerve
Upper subscapular nerve
There are also 3 nerves that emerge from the MEDIAL cord.
Medial cutaneous nerve of FOREARM
The LATERAL cord only has one nerve, which travels to pectoralis major.
Medial cutaneous nerve of ARM
Medial pectoral nerve
Home
Middle subscapular nerve (thoracodorsal)
One final step that could be included, is to review and check your understanding of the various components. Before attempting to draw the brachial plexus on the following page, use the checklist below and click on the interactive elements to help you correctly identifying each feature on this example.
Review...
C5
C6
C7
Checklist tips:
C8
T1
Home
Can you draw the brachial plexus?
Click the paint tool in the top right corner to draw the respective parts of the brachial plexus. Try to have fun by creating your own colour-coding and add as much detail from memory, but feel free to use the homepage button if you would like to retrace the steps by repeating previous sections.
VIDEO
Home
When learning new material, it is often challenging to step back and look for "patterns" to help scaffold. To conclude this section, click the icons to reveal the 5 rules of 5...
Rule of 5's...
Did you spot any other patterns?
Home
What are the functions of the brachial plexus?
Let's add functional context to what each branch of the brachial plexus innervates...
Home
Posterior rami
Motor vs. Sensory neurons:
To reach the roots of the brachial plexus, all motor signals travel through the ventral roots of spinal nerves to exit the spinal cord:
Anterior rami
The word 'ramus' means branch so consider each mixed spinal nerve being like the trunk of a tree with it's roots protected inside the vertebral canal
Sensory axons carry signals from the spinal nerves and enter the spinal cord using the dorsal roots. It is important to differentiate the terminology as the roots of the brachial plexus are actually anterior rami of 'mixed' spinal nerves carrying both types of signal!
Click for summary
Home
INNERVATION
A mixed spinal nerve can carry both motor (efferent) and sensory (afferent) neurons. To understand the destination of where the neural signals are heading, this section has been divided by grouping each nerve of the brachial plexus into the following 3 parts:
Distal branches
Proximal branches
Terminal branches
Let's start by exploring the functions of the 5 main brachial plexus nerves...
Click for a (silly) Mnemonic
Home
Musculocutanous nerve
Click the icons to reveal how neural signals travel through the brachial plexus to form musculocutaneus nerve...
C6
C5
C7
C5
C8
T1
C6
C5, C6 and C7
C7
Lateral cord
C8
Click action for additional info
T1
Flexes forearm at elbow
Skin of lateral forearm
Acland's Video:
See biceps brachii, coracobrachialis + brachialis
Home
Axillary nerve
Click the icons to reveal how neural signals travel through the brachial plexus to form axillary nerve...
C6
C5
C5
C7
C8
T1
C6
C5 and C6
C7
Posterior cord
C8
Click action for additional info
T1
Abducts arm at shoulder
Skin of upper lateral arm
Acland's Video:
See deltoid + teres minor
Home
Median nerve
Click the icons to reveal how neural signals travel through the brachial plexus to form median nerve...
C6
C5
C7
C8
T1
C5
C6
(C5) C6, C7, C8 and T1
C7
Medial + lateral cords
C8
Click action for additional info
Majority of muscles in the anterior forearm
T1
Lateral palm and digits 1-3
Acland's Video:
See the median nerve in the forearm and hand
Median n.erve is located in the centre and forms the middle of the 'm' shape anterior to the axillary artery.
Home
Radial nerve
Click the icons to reveal how neural signals travel through the brachial plexus to form radial nerve...
C6
C5
C7
C8
T1
C5
C6
C5, C6, C7, C8 and T1
C7
Posterior cord
C8
Click action for additional info
Posterior muscles of the arm & forearm
T1
Posterior arm, forearm and lateral dorsal hand
Acland's Video:
See triceps brachii, anconeus + brachioradialis
Acland's Video:
See the radial nerve in the forearm and hand
Home
Ulnar nerve
Click the icons to reveal how neural signals travel through the brachial plexus to form ulnar nerve...
C8
T1
C6
C7
C5
C5
C6
C8 and T1
C7
Medial cord
C8
Click action for additional info
T1
Deep muscles of the hand
Medial hand (palm+dorsum) and digits 4+5
Acland's Video:
See the ulnar nerve in the forearm and hand
Home
INNERVATION
The next part of this section will focus on the branches of the brachial plexus that are associated with the roots and trunks:
Distal branches
Proximal branches
Terminal branches
There are 4 nerves that arise superior to the clavicle...
Home
Dorsal scapular nerve
Click the icons to reveal how neural signals travel through the brachial plexus to form dorsal scapular nerve...
C6
C7
C8
T1
Rhomboid MINOR
Rhomboid MAJOR
C5
Roots
C6
(C4) C5
C7
C8
Click action for additional info
T1
Retraction + elevation of scapula
No
Acland's Video:
See rhomboid major + minor
Home
Suprascapular nerve
Click the icons to reveal how neural signals travel through the brachial plexus to form suprascapular nerve...
C5
C7
C8
T1
Superior trunk
C6
C5 and C6
C7
Anterior view
Posterior view
Suprascapular nerve
Supraspinatus m.
Infraspinatus m.
C8
Click action for additional info
T1
Lateral rotation + first 15° of abduction at shoulder
No
Acland's Video:
See supraspinatus + infraspinatus
Home
Nerve to subclavius
Click the icons to reveal how neural signals travel through the brachial plexus to form nerve to subclavius...
C5
C7
C8
T1
Superior trunk
C6
C5 and C6
C7
Subclavius muscle
Nerve branching from superior trunk
C8
Click action for additional info
T1
Stabilizes & anchors clavicle to 1st rib
No
Acland's Video:
See subclavius
Home
Long thoracic nerve
Click the icons to reveal how neural signals travel through the brachial plexus to form long thoracic nerve...
C5
Roots
C8
T1
Serratus anterior m.
C6
C5, C6 and C7
C7
C8
Click action for additional info
T1
Protracts + anchors scapula against thorax
No
Acland's Video:
See serratus anterior
Home
INNERVATION
The next part of this section will focus on the branches of the brachial plexus that are associated with the cords:
Distal branches
Distal branches
Proximal branches
Terminal branches
With the exception of the terminal branches, there are 7 nerves inferior to the clavicle...
Home
Upper subscapular nerve
Click the icons to reveal how neural signals travel through the brachial plexus to form upper subscapular nerve...
C5
C7
C8
T1
C6
C5 (C6)
C7
Posterior cord
C8
Click action for additional info
T1
Medially rotates arm
No
Acland's Video:
See subscapularis
Home
Lower subscapular nerve
Click the icons to reveal how neural signals travel through the brachial plexus to form lower subscapular nerve...
C5
C7
C8
T1
C6
(C5) C6
C7
Posterior cord
C8
Click action for additional info
T1
Medially rotates arm
No
Acland's Video:
See subscapularis + teres major
Home
Thoracodorsal nerve
Click the icons to reveal how neural signals travel through the brachial plexus to form middle subscapular nerve...
C5
T1
C5
C6
C6, C7 and C8
C7
Posterior cord
C8
Click action for additional info
T1
No
Acland's Video:
See latissimus dorsi
Home
Lateral pectoral nerve
Click the icons to reveal how neural signals travel through the brachial plexus to form lateral pectoral nerve...
C5
C8
T1
C6
C5, C6 and C7
C7
Lateral cord
C8
Click action for additional info
T1
No
Acland's Video:
See pectoralis major
Home
Medial pectoral nerve
Click the icons to reveal how neural signals travel through the brachial plexus to form medial pectoral nerve...
C6
C7
C5
C5
C6
C8 and T1
C7
Medial cord
C8
Click action for additional info
T1
Protracts scapula
No
Acland's Video:
See pectoralis major + minor
Home
Medial cutaneous nerves
Click the icons to reveal how neural signals travel through the brachial plexus to form medial cutaneous nerves...
C5
C6
C7
C5
C6
C7
C5
C6
C8 and T1
C7
Medial cord
C8
T1
No
Home
Review...
To conclude this section, click the paint tool in the top right corner and draw how nerve signals travel through the various parts of the brachial plexus. Click the icons (numbers) on the template for helpful prompts. Understanding where and how the axons typically travel is an important step before attempting the next section.
Superior
Inferior
Lateral
Medial
Home
Clinical Application
After considering the nerves individually, hopefully you noticed there is a degree of overlap in terms of different muscles acting across the various joints. Let's apply some clinical context by working through a few examples of how different types of injury can present in a patient...
Home
Dermatome
Myotome
Myotome:
Dermatome:
In the previous section, specific names (e.g. medial cutaneous n. of the forearm) were given to nerves carrying sensation from the skin.
To be as efficient as possible in a clinical setting, it is important to consider the biomechanical context of muscles working together rather than acting independently.
The stripey organisational pattern is quick to figure out with key landmarks and very easy to measure:
One way to simplify the approach is to focus on primary muscle actions that correlate with specific root levels, for example:
C5 = Sunrise
C5
T1
C6
C8
C7
Home
Clinical Examination
In previous sections, we outlined the motor and sensory distribution of each nerve. When considering how to test the various elements, the American Spinal Injury Association (ASIA) form can be a helpful tool. Watch the video below to see how all of this information can be applied to screen for brachial plexus injuries:
Myotome:
Dermatome:
Home
Clinical presentations:
"Klumpke palsy"
"Erb-Duchenne palsy"
= upper trunk injury!
= lower trunk injury!
C5
C5
C6
C6
C7
C7
C8
C8
T1
T1
Home
Clinical presentation:
If damage occurs to a single nerve branch, the functional deficits will be less extensive and typically affect one group of muscles. When approaching problem based cases, it could be helpful to consider the following questions:
C5
"Winged scapula"
C6
C7
C8
T1
"C5-6-7... wings of heaven"
Home
Quick Clinical Overview
Home
Practice Questions
Spaced repetition is a great way to consolidate learning...
Home
Microsoft Quiz
Now you have worked through the content of this supplementary media, if you would like to complete the anonymous form here will be a selection of questions as well as an opportunity to record feedback on your experience.
Please note the form and practice questions are entirely voluntary, automatically anonymised and free to repeat as many times as you would like!
Mnemonic
Home
Additional Resources
Blank template
Home
Axillary nerve travelling below surgical neck of humerus
Subscapularis muscle
The subscapularis muscle recieves dual innervation, meaning more than one nerve carries motor signals to initiate contraction:
Radial nerve travelling behind shaft of humerus
Upper subscapular nerve
Lower subscapular nerve
Because the muscle fibres insert anteriorly on the lesser tuberosity, this results in INTERNAL (or medial) rotation of the humeral head in the glenoid fossa.
Muscles of the HYPOTHENAR eminence
Couple of medial muscles in the ANTERIOR forearm
= Flexion of metacarpophalageal joints (digits 4+5)
Lumbricals (1/2)
Ulnar canal (of Guyon)
Opponens digiti minimi
= Opposition of digit 5
Abductor digiti minimi brevis
Flexor digiti minimi brevis
Other hand muscles
Adductor pollicis
Flexor carpi ulnaris
= Flexion + adduction of hand at wrist
Palmaris brevis
Palmar interossei
Flexor digitorum profundus (1/2)
= Flexion of distal IP joints (digits 4+5)
Dorsal interossei
Muscles of the THENAR eminence
Most muscles in the ANTERIOR forearm
Pronator teres
Flexor carpi radialis
= Flexion + abduction of hand at wrist
Carpal tunnel
Palmaris longus
= Flexion of hand at wrist
Opponens policis
= Opposition of digit 1
= Flexion of proximal IP joints (digits 2,3,4+5)
Flexor digitorum superficialis
Flexor digitorum profundus (1/2)
= Flexion of distal IP joints (digits 2+3)
Abductor policis brevis
= Flexion of thumb (digit 1)
Flexor pollicis longus
Flexor policis brevis
= Flexion of metacarpophalageal joints (digits 2+3)
Lumbricals (1/2)
Pronator quadratus
Deltoid muscle
Pectoralis major muscle
The lateral pectoral nerve only innervates one muscle: pectoralis major! Pectoralis major is considered to have 2 heads, therefore think of them needing both medial and lateral pectoral nerves for innervation:
Clavicular head
Sternocostal head
Mnemonic:
Organisation of the brachial plexus
Roots
Cords
Trunks
RootsTrunksDivisonsCordsBranches
Divisions
Branches
POSTERIOR terminal branches
The RADIAL nerve is the largest of the terminal branches to supply the upper limb and has a close relationship with the shaft of the humerus:
Axillary n.
Radial n.
Middle subscapular nerve
MIDDLE subscapular nerve can also be called thoracodorsal
The thoracodorsal nerve also goes by the name MIDDLE subscapular because it is sandwiched between the upper and lower, however, it only innervates one muscle:
Latissimus dorsi
The tendon of latissimus dorsi muscle is closely associated with teres major muscle and can be seen twisting to insert to the medial lip of the intertubercular sulcus; thus resulting in INTERNAL (or medial) rotation.
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Conceptual Overview
Sensory neurons:
Motor neurons:
Muscle
Skin
CNS
Efferent ->
<- Afferent
Superficial posterior forearm
POSTERIOR arm
Extensor carpi radialis longus
Anconeus
= Abduction of ulna when pronated
Extensor carpi radialis brevis
Extensor digitorum
Brachioradialis
= Accessory FLEXOR of forearm when mid-pronated
Extensor digiti minimi
Extensor carpi ulnaris
Deep posterior forearm
Supinator
Extensor indicis
Triceps brachii
Extensor pollicis longus
Extensor pollicis brevis
Abductor pollicis longus
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ANTERIOR terminal branches
Musculocutaneous n.
Ulnar n.
Median n.
The characteristic 'm' shape is created when the lateral and medial cords combine to form the MEDIAN nerve located in the 'middle':
Superior
Orientation
Medial
Lateral
Inferior
This image shows the anterior view of the right brachial plexus and starts to provide anatomical context for applying knowledge to the opposite side. The divisions of the brachial plexus are typically located behind the clavicle and help classify supraclavicular versus infraclavicular branches.
Clavicle
NOTE: As the plexus travels laterally, it can also be described as coursing from proximal to distal.
ANTERIOR muscular compartment of the arm
Pierces coracobrachialis muscle
Musculocutaneous n. is the most lateral of the 3 branches helping to form an 'm' shape anterior to the axillary artery.
MOTOR innervation is supplied to the following muscles:
Becomes lateral cutaneous of forearm
Coracobrachialis
= Flexion of arm at shoulder
Biceps brachii
Brachialis
= Flexion of forearm at elbow
Mnemonic:
C6
C5
C7
Nerve roots for the 5 main branches
Musculocutaneous
C6
C5
Axillary
(4 or)
C6
C5
C7
C8
T1
Median
C6
C5
C7
C8
T1
Radial
C8
T1
Ulnar
Long head of biceps brachii tendon forms the intertubercular sulcus
Pectoralis minor muscle
The medial pectoral nerve branches from the medial cord of the brachial plexus close to the ribcage, and typically pierces through the middle of pectoralis minor muscle before also innervating major!
Pectoralis major
Pectoralis minor
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Key:
Posterior triangle of the neck
The roots of the brachial plexus can be found accompaning the subclavian artery as they travel between the anterior and middle scalene muscles - a space also known as the interscalene triangle.
Roots
(and trunks)
Subclavian v.
Rib 1
Quadrangular space
Deltoid muscle is triangular in shape with 3 parts
Axillary n. travels posteriorly around the surgical neck of the humerus and is closely associated with the posterior circumflex humeral branch of the axillary artery.
Axillary nerve supplies MOTOR innervation to:
Deltoid
Teres minor
= Lateral rotation of arm at shoulder
Axillary nerve emerges posteriroly through the quadrangular space
UPPER subscapular nerve
Lower subscapular nerve
The subscapularis muscle recieves dual innervation, meaning more than one nerve carries motor signals to initiate contraction:
LOWER subscapular nerve
Subscapularis muscle
Teres major muscle
Because the muscle fibres insert anteriorly on the lesser tuberosity, this results in INTERNAL (or medial) rotation of the humeral head in the glenoid fossa.
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Use this space to add awesome interactivity. Include text, images, videos, tables, PDFs... even interactive questions! Premium tip: Get information on how your audience interacts with your creation: