Nerves of the Upper Limb Revision Flashcards
What are the roots of the axillary nerve?
C5 and C6
Sensory function of the axillary nerve?
Gives rise to upper lateral cutaneous nerve of arm, which innervates the upper lateral sin of the arm
Motor functions of the axillary nerve?
Innervates deltoid and teres minor
What cord is the axillary nerve formed from?
The posterior cord
In the axilla, where is the axillary nerve located?
Posterior to the axillary artery and anterior to the subscapularis muscle.
Where does the axillary artery exit the axilla?
What is it accompanied by?
Where does it then pass?
At the inferior border of subscapularis via the quadrangular space, accompanied by the posterior circumflex humeral artery and vein
Then passes medially to the surgical neck of the humerus
After passing medially to the surgical neck of the humerus, what happens to the axillary nerve?
Splits into 3 terminal branches:
- Posterior terminal branch
- Anterior terminal branch
- Articular branch
What is the posterior terminal branch of the axillary nerve responsible for?
Provides motor innervation to the posterior aspect of the deltoid muscle and teres minor.
It also innervates the skin over the inferior part of the deltoid as the upper lateral cutaneous nerve of the arm.
What is the anterior terminal branch of the axillary artery responsible for?
Provides motor innervation to the anterior aspect of the deltoid muscle.
How is the sensory component of the axillary nerve delivered?
Via the posterior terminal branch
After the posterior terminal branch of the axillary nerve has innervated the teres minor, what does it continue as?
It continues as the upper lateral cutaneous nerve of the arm –> innervates upper later aspect of arm
What motor functions are affected in axillary nerve injury?
The deltoid and teres minor muscles will be affected, rendering the patient unable to abduct the affected limb.
What sensory functions will be affected in axillary nerve injury?
The upper lateral cutaneous nerve of arm will be affected, resulting in loss of sensation over the upper lateral arm
What are characteristic clinical signs in long standing cases of axillary nerve damage? What muscle atrophies?
The paralysed deltoid muscle atrophies, giving the shoulder a flattened appearance, and the greater tuberosity can be palpated in that area.
What is Erb’s palsy?
Upper brachial plexus injury resulting from damage to C5-C6 (sometimes C7).
The axillary nerve is is affected, and the individual is usually unable to abduct or externally rotate the shoulder joint.
What movement typically causes Erb’s palsy?
Where there is an excessive increase in the angle between the neck and shoulder, which stretches (or even tears) the nerve roots.
What are the roots of the musculocutaneous nerve?
C5-C7
What are the motor functions of the musculocutaneous nerve?
Muscles in the anterior compartment of the arm (coracobrachialis, biceps brachii and the brachialis).
What are the sensory functions of the musculocutaneous nerve?
Gives rise to the lateral cutaneous nerve of forearm, which innervates the lateral aspect of the forearm.
What cord does the musculocutaneous nerve come from?
Terminal branch of the lateral cord
After innervating the anterior arm muscles, describe the route of the musculocutaneous nerve
Emerges lateral to the biceps tendon and brachioradialis.
Continues into the forearm as the lateral cutaneous nerve.
Provides sensory innervation to the lateral aspect of the forearm.
Why is damage to the musculocutaneous nerve uncommon?
It is well protected in the axilla
Injury caused by penetrating trauma (e.g. stabbing) etc
In musculocutaneous nerve injury, how are the motor functions affected?
Coracobrachialis, biceps brachii and brachialis muscles are affected:
- Flexion at the shoulder and elbow are weakened but can still be performed by the pectoralis major and brachioradialis respectively.
- Supination of the forearm is weak, but can still be performed by the brachioradialis.
What are the roots of the median nerve?
C5-T1
