Brachial Plexus Flashcards
Syndrome produced by compression of the components of the brachial plexus, the subclavian artery, or subclavian vein.
Thoracic outlet syndrome
Subtypes of thoracic outlet syndrome
Neurogenic TOS
Anterial TOS
Venous TOS
Positional Compression vs static compression of TOS
Positional: caused by movement of the clavicle and shoulder girdle with arm movement
Static: caused by abnormalities of enlargement of the various muscles surrounding the arteries veins and brachial plexus
What is the brachial plexus formed by
The union of the anterior rami of C5-C8 and T1 (roots of the BP)
In the subclavicular area of the BP, the roots unite to form these trunks:
Superior (upper): C5 and C6
Middle- C7 continues
Inferior- C8 and T1
As the trunks of BP pass lateral to the 1st rib, each trunk:
Splits into ant and post divisions as they pass beneath the clavicle and enter the cervicoaxillary canal
Ant divisions of the BP innervate:
The muscles of the ant compartment in the arm and forearm
Post divisions of the BP innervate:
Muscles of the post compartment of the arm and forearm
BP cords:
Where do they form?
Lateral
Medial
Posterior
Form in the area superior to the pect minor
What forms the lateral cord?
Superior and middle anterior divisions
What forms the medial cord?
Inferior anterior division of the inferior trunk
What forms the posterior cord?
Posterior divisions
Lateral cord becomes the:
Musculocutaneous cord
The medial cord becomes the
Ulnar nerve
The posterior cord becomes the:
Radial nerve
The lateral and medial cord unite together to for the:
Median nerve
Branches from the rami and what they innervate: (2)
Dorsal scapular nerve- rhomboids, levator scapula
Long thoracic nerve— serratus anterior
Branches from trunks/divisions and what they innervate (2)
Nerve to subclavius — subclavius
Suprascapular—- supraspinatus, infraspinatus
Nerves from the cords (7) and what they innervate
Lateral pectoral nerve- pect major
Medial pectoral nerve- pect major and minor
Medial brachial cutaneous nerve— skin, medial arm
Medial antebrachial cutaneous nerve— skin, medial forearm
Lower subscapular nerve- teres major, subscapularis
Upper subscapular nerve— subscapularis
Thoracodorsal nerve— latissimus dorsi
Root branches (3)
Dorsal scapular
Long thoracic
C5 gives a root to the phrenic nerve
Dorsal scapular nerve (_____), and pathway
C5 root
Pierces middle scalene and passes inf. To the rhomboids
Long thoracic nerve pathway
From C5-7 roots passes inferiorly onto the surface of the serratus anterior
Trunk branch, and its pathway
Nerve to subclavius— passes directly to the inf. Surface of clavicle gives branch to sternoclavicular joint
Division branch and its pathway
Subscapular nerve (ant division sup trunk)- runs parallel to the Suprascapular artery to the Suprascapular notch (beneath the suprascapular ligament) supplies the supraspinatus m, around the greater scapular notch to the infraspinatus muscle.
What supplies the scalene and longus coli muscles
Small branches araise from all roots
Big and little branches to lateral cord
Big- musculocutaneous lateral
Small- lateral pectoral
Big and little branches of the posterior cord
Big- axillary radial
Little- upper subscapular, lower subscapular and thoracodorsal
Big and little branches of the medial cords:
Big- ulnar, medial
Little- medial pectoral, medial brachial cutaneous and medial antebrachial cutaneous
Passage of musculocutaneous
Pierces coracobrachialis m and then emerges between the biceps and brachialis, becomes the lateral cutaneous nerve to the forearm- runs parallel to the cephalic vein in the forearm
Muscles innervated by musculocutaneous nerve
Coracobrachialis
Biceps brachial
Brachialis
(Elbow flexors and supinators)
Passage of the lateral pectoral
Pierces the clavicopectoral fascia superior to pect minor- enters the clavicular head of pect major
Passage of axillary branch
Passes through the quadrangular space with post circumflex humeral artery, sends a cutaneous branch and branch to teres minor. Then passes post to surgical neck and supplies deltoid m
Muscle(s) innervated by axillary nerve
Teres minor
Deltoid
Passage of radial nerve
Passes around humerus at radial groove w/ profound a brachii artery to the lateral humerus inf to deltoid insertion.
Runs between the brachioradialis and brachialis m- just proximal to the elbow it divides into the deep and superficial branches
Muscles innervated by radial nerve
Triceps brachii
Brachioradialis
Extensor Capri radialis (branch just proximal to elbow)
Passage of the upper subscapular branch
Passes directly to subscapularis
Muscles innervated by upper subscapular nerve
Subscapularis
Passage of the lower subscapular
Passes directly to subscapularis with a branch to teres major
Muscles innervated by lower subscapular
Subscapularis
Teres major
Passage of ulnar nerve
Follows axillary artery into the arm to accompany the brachial artery- runs medial to the medial epicondyle and enters the forearm between the ulnar and humeral heads of flexor carpi ulnaris
Medial branch forms
Medial nerve
Passage of medial pectoral nerve
Pierces pec minor and enters pec major
Passage of medial brachial cutaneous
Runs parallel and abuts axillary and brachial veins to the medial aspect of the arm
Passage of medial antebrachial cutaneous
Runs with axillary and brachial arteries then runs inferiorly with the basilic vein
Passage of the median nerve
Forms from medial and lateral branches on anterior surface of axillary artery (encircles the axillary artery)- accompanies the brachial artery into the forearm, enters the forearm between the deep and superficial head of the pronator teres
Muscles innervated by median nerve
Pronator teres Flexor carpi radialis Palmaris longus Flexor digitorum superficialis Flexor digitorum profundus (digits 2/3) Flexor policy’s longus Pronator quadratics Thenar muscle Lumbricals 1 and 2
