Flashcards in Lecture 5.2 Deck (48):
Sometimes the brachial plexus can bud out from C4,5,6,7,8 and sometimes from C6,7,8,T1,2. What is the name of these anomalies?
Pre-fixed brachial plexus
Post-fixed brachial plexus
Why is the upper limb innervated by the ventral rami of the spinal nerves?
Upper limb buds out from the anterior body wall and takes with it the ventral nerve supply which is why the ventral rami supply the upper limb.
What is the brachial plexus divided into along its path?
5 Roots -> 3 trunks -> 6 divisions -> 3 cords -> 5 terminal branches
What are the 3 trunks of the brachial plexus?
Superior (C5 - C6)
Inferior (C8 - T1)
What do the 3 trunks divide into?
Each trunk has an anterior and posterior division
What do anterior and posterior division fibers innervate?
Anterior division fibers supply flexor muscles and skin overlying them.
Posterior division fibers supply extensor muscles and skin overlying them.
What structure do the 3 cords of the brachial plexus surround?
The axillary artery
What divisions form the lateral cord of the brachial plexus?
Anterior divisions of the superior trunk and the middle trunk.
What divisions form the medial cord?
Anterior division of inferior trunk continues as the medial cord
What divisions do the anterior and lateral cords contain as a whole?
Lateral and medial cord contain all anterior divisions.
What divisions form the posterior cord?
All 3 posterior divisions form the posterior cord.
What structures form the M shape of the brachial plexus?
M shape formed by the terminal branches of the lateral and medial cord
Where are the cords formed relative to the clavicle?
inferior to the clavicle the cords are formed
What nerve arises from the upper limb of the 'M'? What cord can this nerve be traced back to?
upper limb of the m pierces coracobrachialis this is the musculocutaneous nerve. This can be traced back to the lateral cord
What is the terminal branch formed by the middle limb of the 'M'?
Middle limb of the m is the median nerve. It has a root from the lateral cord and the medial cord.
What is the terminal branch formed by the lower limb of the 'M'?
Lower limb of the m is the ulnar nerve.
Which nerve pierces coracobrachialis?
The musculocutaneous nerve
What 2 muscles does the musculocutaneous nerve run through?
Deep to the Biceps and superficial to the brachialis
What happens to the musculocutaneous nerve after it runs out of motor branches?
Musculocutaneous nerve continues after the elbow and becomes the lateral cutaneous nerve of the forearm supplying the skin of the lateral side of the forearm.
What roots does the ulnar nerve get?
Ulnar nerve is a branch of the medial cord of the brachial plexus which was formed by the anterior division of the lower trunk. Most people get some contribution from C7. But is mainly innervated by C8 and T1.
Where does the ulnar nerve run in the arm?
ulnar nerve runs down medial side of the brachial artery and then moves under the medial epicondyle. It is vulnerable to trauma at that location.
Where does the ulnar nerve run in the forearm?
In forearm ulnar nerve is found under the Flexor carpi ulnaris and then runs superficially to the flexor retinaculum into the palm of the hand.
What does the ulnar nerve supply?
ulnar nerve primarily supplies the hand with the exception of the lateral 2 lumbricals, the opponens pollicis, the abductor pollicis brevis, and the flexor pollicis brevis. (1 '+ 2' LOAF which is a mnemonic for the thenar eminence muscles which are innervated by the median nerve)
What muscles of the forearm does the median nerve supply?
Median nerve supplies the anterior compartment of the forearm. exception is FCU and the medial 2 heads of FDP.
What muscles in the palm of the hand does the ulnar nerve innervate?
Everything in the palm of the hand except what the median nerve does. (1'+2' LOAF)
What is the cutaneous distribution of the ulnar nerve?
ulnar nerve does medial 1 and a half fingers anteriorly and posteriorly.and the palm underneath
What nerve roots, divisions, and cords does the median nerve arise from?
Median nerve comes from median and lateral cords and is formed by all the anterior divisions. from ventral rami of C5,6,7,8,T1.
How does the median nerve travel along the arm?
Median nerve is found either lateral to or anterior to the brachial artery. This nerve crosses the brachial artery medially into the cubital fossa.
What are the contents of the cubital fossa from laterally to medially?
Radial Nerve then Tendon of biceps then brachial artery then the median nerve. (RBAN from laterally to medially)
What is the cutaneous distribution of the median nerve?
Anteriorly all the palm and 3 and a half fingers from lateral hand to medial.
Posteriorly the tips of the fingers of the area the median nerve innervates anteriorly.
How does the median nerve travel through the forearm?
Median nerve enters anterior compartment of the forearm underneath the arch of FDS. Fibrous Arch of FDS created by origin at the radius and the medial epicondyle. Median nerve runs superficially to FDP and deep to FDS' fibrous arch
What nerves supply the lumbricals?
medial 2 lumbricals supplied by the ulnar nerve and lateral 2 lumbricals by the median nerve.
Why is there no tingling or numbness during carpal tunnel syndrome?
Palmar cutaneous nerve goes over the flexor retinaculum to supply the cutaneous nerve supply and so it isn't entrapped with the rest of the median nerve.
Where in the brachial plexus do the radial and axillary nerves arise from?
Posterior cord contains all posterior divisions and creates the radial and axillary nerves.
What spaces do the axillary nerve and radial nerve go into the posterior compartment and where is this relative to teres major?
Axillary nerve goes above teres major and below teres minor (quadrangular space) and radial nerve below teres major (triangular interval).
What spinal roots does the axillary nerve receive its innervation from?
Why is shoulder dislocation a problem for the axillary nerve?
The anterior branch of the axillary nerve goes through quadrangular space and then winds around the humeral surgical neck along with posterior humeral circumflex artery. Shoulder dislocation can damage this branch.
What muscles does axillary nerve supply?
Long head of the triceps (not mentioned in lectures but found in many sources I read)
What branches of the axillary nerve supply the deltoids?
anterior and posterior branches of axillary nerve supply deltoids
What structures does the radial nerve supply?
Radial nerve supplies triceps and posterior compartment of the forearm.
What is the pathway the radial nerve takes in the arm?
emerges beneath teres major and spirals around the back of the humerus and follows profunda brachii artery. Radial nerve branches off really early and at the spiral groove it sends off branches to the posterior compartment of the forearm.
What muscle does the radial nerve go under in the forearm?
What structures pass under brachioradialis?
The radial nerve and artery
What branch does the radial nerve give off before heading under brachioradialis?
before the radial nerve splits under the cover of brachioradialis it gives off all of its motor fibers via the posterior interosseus nerve which runs deeply and supplies all the extensor compartment of the forearm's muscles
What is the cutaneous distribution of the radial nerve in the hand?
the dorsum of the hand with the exception of the nailbeds.
What cutaneous nerves supply the lateral side of the arm and forearm?
Axillary nerve over the deltoids.
Radial nerve on the lateral side of the arm.
Musculocutaneous nerve on the lateral side of the forearm gives off a branch called the lateral cutaneous branch of the forearm.
What cutaneous nerves supply the medial side of the arm and forearm?
Skin down medial side of the arm is by medial cutaneous nerve of arm and forearm. These are direct branches of the medial cord.