Dissection 9- Brachial Plexus Flashcards
Where is the brachial plexus found?
It begins in the lateral cervical region (posterior triangle) and extends into the axilla
What forms the brachial plexus?
The union of the anterior rami of C5-T1 nerves
The anterior rami of C5-T1 constitute what part of the plexus?
The roots
What are the different regions of the brachial plexus, from proximal to distal?
- Roots
- Trunks
- Divisions
- Cords
- Nerves (terminal branches)
Where are the roots and trunks of the brachial plexus found?
Mainly between the anterior and middle scalene muscles in the root of the neck
Where are the divisions of the brachial plexus found?
Immediately posterior to the subclavian vessels in the root of the neck
Where are the cords of the brachial plexus found?
Around the axillary artery which is distal to the 1st rib
In the inferior part of the neck, the roots of the brachial plexus unite to form what?
3 trunks
What are the names of the three trunks of the brachial plexus?
- Superior
- Middle
- Inferior
What forms the superior trunk?
The union of C5 and C6 roots
What forms the middle trunk?
A continuation of the C7 root
What forms the inferior trunk?
The union of C8 and T1 roots
What does each trunk of the brachial plexus divide into?
Anterior and posterior divisions
Where in the body do the trunks divide into divisions?
As the plexus passes through the cervico-axillary canal, posterior to the clavicles
What do anterior divisions supply?
Anterior (flexor) compartments of the upper limb
What do posterior divisions supply?
Posterior (extensor) compartments of the upper limb
What do the divisions of the brachial plexus form?
3 cords
What are the three cords of the brachial plexus known as?
- Lateral cord
- Posterior cord
- Medial cord
What forms the lateral cord?
Anterior divisions of the superior and middle trunks
What forms the medial cord?
A continuation of the anterior division of the inferior trunk
What forms the posterior cord?
The posterior divisions of all three trunks
The cords of the brachial plexus are named according to their relation to where?
Second part of the axillary artery
What are the 5 named nerves of the brachial plexus?
- Musculocutaneous nerve
- Axillary nerve
- Radial nerve
- Median nerve
- Ulnar nerve
What forms the musculocutaneous nerve?
A direct continuation of the lateral cord
What muscle does the musculocutaneous nerve enter?
Coracobrachialis
What muscles does the musculocutaneous nerve supply?
Muscles of the anterior compartment of the arm: coracobrachialis, biceps brachii and brachialis
What forms the axillary nerve?
The posterior cord splits in two, one of these branches is the axillary nerve
What forms the radial nerve?
The posterior cord splits in two, one of these branches is the radial nerve
The posterior cord splits in two to form what?
Axillary and radial nerves
The axillary and radial nerves pass into what compartment of the arm?
Posterior
Where does the axillary nerve lie?
Superior to the radial nerve, wrapped around the posterior aspect of the surgical neck of the humerus
What injuries make the axillary nerve susceptible to injury?
- Shoulder dislocations
- Fractures of the humeral neck
Where does the radial nerve lie?
Wraps around the posterior aspect of. the mid-shaft of the humerus
What injury makes the radial nerve susceptible to injury?
Mid shaft of the humerus fractures
What forms the median nerve?
Formed from the combination of the medial and lateral cords
What nerve forms the middle of the M shaped configuration of the named nerves of the brachial plexus?
Median nerve
What forms the ulnar nerve?
A direct continuation of the medial cord
What is the most medial named nerve?
Ulnar nerve
What area of the arm does the ulnar nerve pass into?
Medial
What are the branches of the brachial plexus which come from the roots AND their corresponding nerve root numbers?
- Long thoracic nerve (C5, 6, 7)
- Dorsal scapular nerve (C5)
- First intercostal nerve (T1)
What muscle does the long thoracic nerve supply?
Serratus anterior
What muscles does the dorsal scapular nerve supply?
Rhomboids and elevator scapulae
What are the branches of the brachial plexus which come from the superior trunk AND their corresponding nerve root numbers?
- Suprascapular nerve (C5/6)
- Nerve to subclavius (C5/6)
What does the supra scapular nerve supply?
Supra and infraspinatus
What nerve branches from the lateral cord?
Lateral pectoral nerve (C5, 6, 7)
What does the lateral pectoral nerve supply?
Pectoralis major
What nerves branch from the posterior cord?
- Upper sub scapular nerve (C5, 6)
- Lower sub scapular nerve (C5, 6)
- Thoracodorsal nerve (C6, 7, 8)
What does the upper sub scapular nerve supply?
Subscapularis
What does the lower sub scapular nerve supply?
Subscapularis and teres major
What does the thoracodorsal nerve supply?
Latissimus dorsi
What nerves branch from the medial cord?
- Medial pectoral nerve (C8, T1)
- Medial cutaneous nerve of arm (T1)
- Medial cutaneous nerve of forearm (C8)
What does the medial pectoral nerve supply?
Pectorals major and minor
Injury to the upper brachial plexus constitutes what nerve roots?
C5, C6
What is usually the cause of upper brachial plexus injury?
An excessive increase in angle between the neck and shoulder
How does upper brachial plexus injury cause the upper limb to hang?
In medial rotation
Which is more common, upper or lower brachial plexus injuries?
Upper
What may cause lower brachial plexus injury?
When the upper limb is pulled superiorly
Injury to the lower brachial plexus constitutes what nerve roots?
C8, T1
Lower brachial plexus injury results in the formation of what?
Claw hand
