Brachial and Lumbo-Sacral Plexuses Flashcards
Where is the axilla located ?
Between lateral wall of thorax and the humerus.
What are the boundaries of the axilla ?
- Anterior wall
- Medial wall
- Lateral wall
- Posterior wall
- Base (armpit)
- Apex (axillary inlet for neurovascular structures)
What are the important surface axillary lines ?
Anterior Axillary line
Midaxillary line
Posterior Axillary line
What is the anterior wall of the axilla made of ? Describe each component, including where they attach.
3 muscles and 1 deep fascia
Muscles: Pectoralis major (anterior axillary fold) + Pectoralis minor + Subclavius (attaches at first rib and to inferior surface of clavicle)
Fascia: Clavipectoral fascia (deep): Continuous with neck fascia. Splits to enclose Pectoralis minor and Subclavius. Structures passing anteriorly must pierce the fascia. Attaches to skin of the armpit
What is the medial wall of the axilla made of ?
1 muscle and 4 bones
Bones: Ribs 1-4 and intercostal spaces
Muscles: Serratus anterior
What is the lateral wall of the axilla made of ?
2 muscles and 1 bone
Bone: Bicipital groove of the humerus
Muscles: Proximal parts of Biceps and Coracobrachialis (potentially)
What is the posterior wall of the axilla made of ?
3 muscles and 1 bone
Muscles: Subscapularis + Teres major + Latissimus dorsi
Bone: Scapula
What are the roots of the brachial plexus ?
Anterior rami of C5-T1
What muscles do the anterior rami of C5-T1 pass through to enter the axilla ?
Between anterior and middle scalene muscles
Which anterior rami form which trunk in the brachial plexus ?
Ventral rami of C5 and C6 join and form the superior trunk
Ventral ramus of C7 forms the middle trunk
Ventral rami of C7 and T1 join and form the inferior trunk
Where are trunks formed, in the brachial plexus ?
In the posterior cervical triangle
What is the next division in the brachial plexus, following trunks ?
Each trunk is divided into an anterior and posterior divisions
What is the next division in the brachial plexus, following anterior and posterior divisions of trunk ?
Posterior cord from posterior divisions of all trunks
Lateral cord from anterior divisions of superior and middle trunks
Medial cord from anterior division of inferior trunk
Cords of the brachial plexus are named according to their position relative to what structure ?
The axillary artery
What are the nerve branches of the anterior rami of the brachial plexus ? What does each nerve supply ? Are they sensory/motor ?
Long Thoracic nerve - descend on the ribs to supply serratus anterior (motor only)
Dorsal Scapular nerve - pierces middle scalene muscle, passes posteriorly to the back to supply levator scapulae and the rhomboids (motor only)
What are the nerve branches of the trunks of the brachial plexus ? What does each nerve supply ? Are they sensory/motor ?
Only the upper trunk had branches.
Suprascapular nerve - passes posteriorly to the scapular region via suprascapular notch to supply supraspinatus and infraspinatus muscles (motor only)
Nerve to Subclavius - supplies subclavius (motor only)
What are the nerve branches of the divisions (posterior/anterior) of the brachial plexus ?
No branch arises directly from the divisions
What do anterior and posterior divisions of the brachial plexus supply respectively ?
Anterior divisions supply muscles of the anterior wall of the axilla, flexor muscles of the limb and skin that overlies those muscles
Posterior divisions supply muscles of the posterior wall of the axilla, extensor muscles and skin that overlies those muscles
Where are the cords (of the brachial plexus) located in the body, relative to surrounding structure(s) ?
Around the 2nd part of axillary artery
What nerve(s) branches out of the lateral cord of the brachial plexus ? What does each nerve supply ? Are they sensory/motor ?
Lateral pectoral nerve passes anteriorly to supply pectoralis major (motor only)
What nerve(s) branches out of the posterior cord of the brachial plexus ? What does each nerve supply ? Are they sensory/motor ?
Upper Subscapular nerve passes posteriorly to the scapular region to supply subscapularis (motor only)
Thoracodorsal nerve passes inferiorly with its artery to supply latissimus dorsi (motor only)
Lower Subscapular nerve passes posteriorly to the scapular region to supply subscapularis and teres major (motor only)
What nerve(s) branches out of the medial cord of the brachial plexus ? What does each nerve supply ? Are they sensory/motor ?
Medial pectoral nerve passes anteriorly often pierces pectoralis minor and supplies both pectoralis major and minor (motor only)
Medial cutaneous nerve of arm passes into the arm supplies skin (sensory only)
Medial cutaneous nerve of forearm passes into the forearm, travels with the basilic vein supplies skin (sensory only)
What are the main terminal branches (peripheral nerves) of the brachial plexus ?
Radial nerve
Axillary nerve
Musculocutaneous nerve
Median nerve
Ulnar nerve
Which roots does each terminal branch of the brachial plexus originate from ?
Radial nerve - C5-T1
Axillary nerve - C5-C6
Musculocutaneous nerve - C5-C7
Median nerve - C6-T1
Ulnar nerve - C7-T1