Brachial Plexus Flashcards
What are the 5 parts of the brachial plexus?
Roots, Trunks, Division, Cords and branches
remember: Read That Damn Cadaver Book
What forms the roots of the brachial plexus?
The spinal nerves C5, C6, C7, C8, T1
How do the spinal nerves leave the spinal cord?
Intervertebral foramina of the vertebral column
Each nerve divides into an anterior and posterior fibre, the roots of the brachial plexus are formed by which of these divisions?
Anterior division of spinal nerves C5-T1
After their formation the nerves at the roots of the brachial plexus pass between what to enter the base of the neck?
Anterior and medial scalene
At the base of the neck , the roots of the brachial plexus converge to form trunks,h ow many trunks are there and what are they called?
3
Superior
Middle
Lateral
Which nerves does the superior trunk of the brachial plexus consist of?
C5 and C6
Which nerves does the middle trunk of the brachial plexus consist of?
C7
Which nerves does the inferior trunk of the brachial plexus consist of?
C8 and T1
Within the posterior triangle of the neck, each trunk of the brachial plexus divides into branches. How many branches does each trunk divide into and which way do they travel? What are the branches called?
Each trunk divides into 2 branches
Travelling anterior and posteriorly
The branches are therefore called the anterior and posterior division
this is the division section of the brachial plexus
What route do the 3 anterior and 3 posterior divisions take in the brachial plexus?
Leave the posterior triangle of the neck and pass into the axilla region
they will recombine in the next part of the brachial plexus
What are the names given to the 3 nerves that are formed by the recombination of the divisions in the brachial plexus?
Lateral
Posterior
Medial
so name because of their position relative to the axillary artery
What is the lateral cord of the brachial plexus formed by?
Anterior division of the superior trunk
Anterior division of the middle trunk
What is the posterior cord of the brachial plexus formed by?
Posterior division of the superior trunk
Posterior division of the middle trunk
Posterior division of the inferior trunk
What is the medial cord of the brachial plexus formed by?
Anterior division of the inferior trunk
What do the cord of the brachial plexus give rise to?
The major branches
What are the roots of the musculocutaneous nerve?
C5, C6, C7
Remember: 3 musketeers assassinated 5 mice, 5 rats and 2 unicorns
What are the motor functions of the musculocutaneous nerve?
Brachialis, bicep brachii, coracobrachialis
remember:BBC
What are the sensory functions of the musculocutaneous nerve?
Gives off the lateral cutaneous branch of the forearm, which innervates the lateral half of the anterior forearm and a small lateral portion of the posterior forearm
What are the roots of the axillary nerve?
C5 and C6
Remember: 3 musketeers assassinated 5 mice, 5 rats and 2 unicorns
What are the motor functions of the axillary nerve?
Innervates the teres minor and the deltoid muscles
What are the sensory functions of the axillary nerve?
Gives off the superior lateral cutaneous nerve of arm, which innervates the inferior region of the deltoid (regimental badge area)
What are the roots of the median nerve?
All (C5-T1)
Remember: 3 musketeers assassinated 5 mice, 5 rats and 2 unicorns
What are the motor functions of the median nerve?
Innervates most of the flexor muscles in the forearm, the thenar muscles and the two lateral lumbricals that move the index and middle fingers
What are the sensory functions of the median nerve?
Gives off the palmar cutaneous branch which innervates the lateral part of the palm and the digital cutaneous branch, which innervates the lateral three and a half fingers on the anterior (palmar) surface of the hand
What are the roots of the radial nerve?
C5-8 and T1
Remember: 3 musketeers assassinated 5 mice, 5 rats and 2 unicorns
What are the motor functions of the radial nerve?
Innervates the tricep brachii and the extensor muscles in the posterior compartment of the forearm
What are the sensory functions of the radial nerve?
Innervates the posterior aspect of the arm and forearm, and the posterior, lateral aspect of the hand
What are the roots of the ulnar nerve?
C8 and T1
Remember: 3 musketeers assassinated 5 mice, 5 rats and 2 unicorns
What are the motor functions of the ulnar nerve?
Innervates the muscle of the hand (apart from the thenar muscle and two lateral lumbricals), flexor carpi ulnaris and medial half of flexor digitorum profundus
What are the sensory functions of the ulnar nerve?
Innervates the anterior and posterior surfaces of the medial one and half fingers and associated palm area
When looking at the brachial plexus, find the structure that is an ‘M’ shape, what nerves have you found here?
The musculocutaneous, median and ulnar nerves
They will be arranged around the brachial artery
(Can use this M to get your bearings and work back to find the roots etc)
There are also many minor branches of the brachial plexus, name the minor branches off the roots
Doral scapular nerve
Long thoracic nerve
There are also many minor branches of the brachial plexus, name the branches off the trunks
Suprascapular nerve
Nerve to subclavian
There are also many minor branches of the brachial plexus, name the branches off the medial cord
Medial pectoral nerve
Medial cutaneous nerve of arm
Medial cutaneous nerve of forearm
There are also many minor branches of the brachial plexus, name the branches off the lateral cord
Lateral pectoral nerve
There are also many minor branches of the brachial plexus, name the branches off the posterior cord
Superior subscapular nerve
Thoracodorsal nerve
Inferior subscapular nerve
What does an upper brachial plexus injury affect?
The superior roots
What does a lower brachial plexus injury affect?
The inferior roots
What does upper brachial plexus injury cause?
Erb’s palsy
What causes Erb’s palsy?
When there is excessive increase in the angle between the neck and shoulder- stretches or even tears the nerve roots
What nerves are affected by Erb’s palsy?
Nerves derived from solely C5 or C6 roots:
Musculocutaneous, axillary, suprascapular and nerve to subclavius
What muscles become paralysed as a result of Erb’s palsy?
Supraspinatus, subclavius, bicep brachii, brachialis, coracobrachialis, deltoid and teres minor
What motor functions are lost of greatly weakened by Erb’s palsy?
Abduction at shoulder
Lateral rotation of arm
Supination of forearm
Flexion at shoulder
What sensory functions are lost when someone has Erb’s palsy?
Loss of sensation down lateral side of arm, which covers the sensory innervation of the axillary and musculocutaneous nerves
Why would an arm affected by Erb’s palsy hand limply and medically rotated?
Limp due to paralyse
Medially rotated because of unopposed action of pectoralis major
What position if characteristic of Erb’s palsy?
The waiters’ tip
What is an injury to the lower brachial plexus called?
Klumpke palsy
When down klumpke palsy occur?
When there is excessive abduction of the arm (eg Person catching a branch as they fall from a tree)
What nerves are affected by klumpke palsy?
Those derived form T1
Radial
Median
and ulnar
What muscles are paralysed when someone has klumpke palsy?
All the small muscles of the heads (the flexor muscles in the forearm are supplied by the ulna and median nerve but are innervated by different roots)
What happens to someone sensory function when they have klumpke pulsy?
They get loss of sensation along media side of arm
What is a characteristic of klumpke palsy and why?
A clawed hand
Due to the hyperextended metacarpophalangeal joints and the flexed interphalangeal joints
Which group of muscles does the median nerve innervate the majority of?
Anterior forearm
