Brachial Plexus Flashcards
The brachial plexus is a […] plexus formed by ventral rami of […] - […]
Somatic
C5 - T1
What does the brachial plexus innervate (in general)?
Provides all motor and sensory innervation to muscles and skin of upper extremity and most of shoulder and extrinsic back muscles
Describe the structure of the brachial plexus.
5 ventral rami come together to form 3 trunks (superior, middle, inferior), which then split into 3 anterior and 3 posterior divisions (relative to axillary artery). Divisions come together in axilla to form 3 cords (Lateral, posterior and medial; also named for relationship to axillary artery). The 3 cords then end in 5 terminal branches (axillary nerve, radial nerve, median nerve, ulnar nerve, musculocutaneous nerve).
What are the 3 nerves that make up the “M” of the axilla?
Musculocutaneous
Median (contributions from lateral and medial cords)
Ulnar nerve
Describe the structure of the 3 trunks of the brachial plexus.
Ventral rami of C5 and C6 form the superior trunk
Ventral ramus of C7 forms the middle trunk
Ventral rami from C8 and T1 form the inferior trunk
Describe the formation of the cords of the brachial plexus.
- All 3 posterior divisions come together to form the posterior cord
- The superior, anterior division becomes the lateral cord
- The inferior, anterior division becomes the medial cord
Describe the formation of the 5 terminal nerves of the brachial plexus.
- Posterior divides to form axillary nerve and continue on as radial nerve (axial divides off superior to radial)
- The lateral cord divides to form the musculocutaneous nerve and part of the median nerve
- The medial cord divides to form the ulnar nerve and part of the median nerve
What nerve comes directly off of the C5 ventral ramus of the brachial plexus?
What muscle(s) does this nerve innervate?
The dorsal scapular nerve
The levator scapulae and the rhomboid major + minor
What are the origins of the long thoracic nerve?
What muscle(s) does this nerve innervate?
It arises from the ventral rami of C5, 6 and 7 in the brachial plexus.
It innervates the serratus anterior.
What are the origns of the suprascapular nerve?
What is unique about this nerve?
What muscle(s) does it innervate?
It arises from the upper trunk.
It is the only nerve to arise from a trunk of the brachial plexus.
It innervates the supraspinatus and the infraspinatus.
Describe the origins of the medial and lateral pectoral nerves.
What muscle(s) do these nerves innervate?
They arise from the medial and lateral cords of the brachial plexus, respectively.
Pectoralis major (both) and pectoralis minor (medial only)
What nerves originate from the posterior cord?
What muscles do these innervate?
The subscapular nerve (innervates subscapularis and teres major) and the thoracodorsal nerve (innervates latissimus dorsi)
- Describe the location of the radial nerve.
- What muscles does it innervate?
- It provides sensation to what parts of the forearm?
- It wraps around the humerus in the radial groove.
- Triceps and muscles of posterior forearm
- Skin of posterior arm, forearm and dorsal hand
A humeral surgical neck fracture is most likely to damage which nerve?
The axillary nerve
A mid-shaft humeral fracture is most likely to damage which nerve?
The radial nerve
