Limbs 2 Flashcards
What is a nerve plexus?
A nerve plexus is formed when peripheral spinal nerve roots merge and split to produce a network of nerves from which new multi-segmental peripheral nerves emerge.
What are the roots of the brachial plexus?
C5,6,7,8 and T1
Describe the organisation of the brachial plexus?
- The roots from the spine (C5-T1) enter the inferior neck where they form 3 trunks
- These trunks pass under the clavicle to enter the axillary region where they form 6 divisions
- The divisions merge to form 3 distinct cords
- In the distal part of the axilla the cords branch to form the main terminal nerves.
What are the branches of C5 at the roots of the brachial plexus?
- Dorsal scapular nerve
- Contribution to phrenic nerve
- Long thoracic nerve
Which muscles does the dorsal scapular nerve innervate?
- Rhomboids
- Levator scapulae
Which muscle does the long thoracic nerve and what does damage to THE NERVE cause
Serratus anterior
Winged scapula due to paralysis of serratus anterior
The long thoracic nerve also receives fibres from other roots whcih ones?
C5, C6, C7
How is the superior trunk of the brachial plexus formed
Roots of C5 and 6 merge
What are the 2 branches of the superior trunk of the brachial plexus?
- Nerve to subclavius
- Suprascapular nerve
What muscles do the suprasccapular nerve innervate?
- Infraspinatus
- Supraspinatus
How is the middle trunk of the brachial plexus formed?
C7 continuation
How is the inferior trunk of the brachial plexus formed?
C8 and T1 merges
What types of structures do the fibres of the anterior and posterior divisions innervate?
- Anterior fibres innervate anterior structures
- Posterior fibres innervate posterior structures
How is the lateral cord of the brachial plexus formed?
Anterior divisions from the superior and middle trunks merge
What is the non-terminal branch of the lateral cord?
Lateral pectoral nerve
Which muscle does the lateral pectoral nerve supply?
Pec major
How is the posterior cord of the brachial plexus formed
All 3 posterior divisions of each trunk merge to form the posterior cord
What are the branches of the posterior cord?
- Superior subscapular nerve - subscapularis and teres major
- Thoracodorsal nerve - lat dorsi
- Inferior subscapular nerve - teres major + subscapularis
- Axillary nerve - teres minor and deltoid
How is the medial cord of the brachial plexus formed?
The anterior division of the inferior trunk merges to form the medial cord
What are the branches of the medial cord of the BP?
- Medial pectoral nerve
- Medial cutaneous nerve of arm
- Medial cutaneous nerve of forearm
Which muscles do the medial pectoral nerve innervate?
- Pec minor
- part of pec major
How are the cords named in relation to the axillary artery AND their function
Example is best: The posterior cord is posterior to the artery and mostly serves posterior structures etc
What is the other name for terminal branches of the brachial plexus?
Peripheral nerves
What are the supraclavicular nerves?
Nerves that branch off the brachial plexus proximal (above - supra) to the clavicle from the roots and superior trunk to supply some of the scapular muscles
What are the infraclavicular nerves?
Nerves that branch from the distal parts of the plexus inferior to the clavicle in the axilla
What 2 subgroups can the infraclavicular nerves be divided into
- The side branches to individual muscles or specific cutaneous regions eg. scapular muscles
- The large terminal branches which innervate numerous structures in the arm, forearm and hand eg. radial ulnar median
origin and innervation
What is the musculotaneous nerve?
- It is a terminal branch of the lateral cord
- Muscular innervation to the anterior muscles of the arm
- Cutaneous innervation of the lateral forearm
Describe how the musculocutaneous nerve moves through the arm and forearm
- Pierces coracobrachialis and branches to reach biceps and brachialis muscles.
- Continues to cross the elbow joint to innervate the lateral arm
What is the name of the branch of the musculocutaneous nerve that supplies cutaneous innervation to the lateral forearm?
Lateral cutaneous nerve of the forearm
What is the ulnar nerve?
The terminal branch of the medial cord of the brachial plexus
Where does the ulnar nerve supply innervation?
- Cutaneous innervation of the medial hand
- Branches to medial forearm muscles at elbow -
- Branches to intrinsic muscles of hand at wrist
Which muscles does the ulnar nerve innervate when passing through the forearm?
- Flexor carpi ulnaris
- Medial half of flexor digitorum profundus
How does the ulnar nerve enter the hand and which muscles does it innervate there?
Crosses the wrist and terminal braches innervate most of the intrinsic muscles incl.
* Hypothenar eminence muscles,
* 2 medial lumbricals
* Palmar and dorsal interossei
Where does the ulnar nerve supply cutaneous innervation?
The medial hand including the little finger and the medial half of the ring finger.
Describe the organisation of the ulnar nerve?
- Passes from the axilla
- Then passes posteriorly to the medial epicondyle of the humerus where it can be palpated and is susceptible to injury
What part of the brachial plexus is the median nerveformed from?
Formed from the lateral and medial cords
Describe how the median nerve passes through the upper limb?
- Passes distally out of the axilla to run medially in the arm
- Crosses the elbow joint via cubital fossa medial to brachial artery into the forearm
- Crosses the wrist and enters the hand via the carpal tunnel
- Passes under the flexor digitorum and gives off terminal branches when it enters the hand