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
What cord is each terminal branch a branch of (in the brachial plexus) ?
Radial and axillary nerve - branches of the posterior cord
Musculocutaneous nerve - branch of the lateral cord
Median nerve - formed by the union of Lateral root (C6- C7, from the lateral cord) and the medial root of the median nerve (C8-T1, from the medial cord)
Ulnar nerve - branch of the medial cord
Where does the radial nerve pass in order to reach its final destination ?
Crosses the tendon of latissimus dorsi, passes posteriorly through the lower triangular space with profunda brachii artery
Where does the axillary nerve pass in order to reach its final destination ?
Passes posteriorly through the
quadrilateral space, lies on the surgical neck of the humerus with the posterior circumflex humeral artery
Where does the musculocutaneous nerve pass in order to reach its final destination ?
Pierces coracobrachialis and travels between brachialis and biceps brachii
Where does the median nerve pass in order to reach its final destination ?
Travels with the brachial artery
Where does the ulnar nerve pass in order to reach its final destination ?
Passes posterior to the elbow
What does the radial nerve supply ?
- All extensor muscles of arm and forearm
- Posterior skin of arm, forearm and hand
What does the axillary nerves supply ?
-Deltoid and teres minor
-Skin over the lower part of deltoid
What does the musculocutaneous nerve supply ?
- Flexor compartment of the arm (biceps brachii, brachialis, coracobrachialis)
- Becomes the lateral cutaneous nerve of the forearm
What does the median nerve supply ?
-All flexor muscles of the forearm (except 11⁄2), thenar muscles (except 1) and lateral 2 lumbricals
-Skin over the lateral palmar surface of hand and lateral 31⁄2 digits including nail beds
What does the ulnar nerve supply ?
- 11⁄2 flexors of the forearm
- 1 thenar muscle, all hypothenar and interosseal muscles and medial 2 lumbricals
- Skin over the medial palmar surface of hand and medial 11⁄2 digits
What parts of the body does the lumbo-sacral plexus innervate ?
Lower limbs, and parts of the pelvis and perineum
What are the roots of the lumbar plexus ?
L1 to L4
What are the roots of the sacral plexus ?
L4-L5 and S1 to S4
How do the L4 and L5 communicate with the sacral plexus ?
Via the lumbosacral trunk
What are the main nerves from the lumbosacral plexus entering the thigh ? Which roots does each originate from ?
Femoral nerve (L2-L4) Sciatic nerve (L4-S3)
Where is the lumbar plexus located relative to surrounding structures ?
Within the substance of the psoas major muscle and anterior to the transverse processes of the lumbar vertebrae.
Does the lumbar plexus have sensory/motor/both branches ?
It has both motor and sensory branches
Where is the sacral plexus located relative to surrounding structures ?
On the surface of the posterior pelvic wall, anterior to the piriformis muscle.
What are the main nerves from the sacral plexus ? Indicate for each whether it is motor, sensory, or both.
Superior gluteal (motor) -
Inferior gluteal (motor)
Sciatic (motor and sensory)
Posterior femoral cutaneous (sensory)
Nerve to Piriformis
Obturator internus
Quadratus femoris
What do nerves originating from the sacral plexus innervate ?
Gluteal region and lower limb
Where does the femoral nerve pass ?
Descends in the abdomen, travels through the pelvis to the mid point of the inguinal ligament.
Traverses behind the inguinal ligament into the thigh.
Passes through the femoral triangle.
What is the terminal cutaneous branch of the femoral nerve ? What does this nerve enter ?
Saphenous nerve
Enters the adductor canal with the femoral artery and vein
What does the femoral nerve supply ?
Some of the anterior thigh muscles (hip flexors, knee extensors)
Skin of anteromedial thigh and medial leg and foot (the latter via its terminal branch, the saphenous nerve)
Where does the sciatic nerve pass ?
Enters the gluteal region inferior to piriformis (infrapiriform space/greater sciatic foramen)
Runs deep to gluteus maximus and lateral rotators of the thigh, midway between the ischial tuberosity and the greater trochanter, behind the hip joint
In the posterior compartment of the thigh, it descends between the adductor magnus and biceps femoris
Does the sciatic nerve supply any structure in the gluteal region ?
No
What does the sciatic nerve supply ?
Hamstring muscles (thigh extensors, leg flexors) Adductor magnus, in addition to the obturator nerve
Where does the sciatic nerve give off its terminal branches ?
At the apex of the popliteal fossa but in some cases near the piriformis
What are the two main branches given off by the sciatic nerve ? Which of the two if the larger one ?
Tibial nerve (larger one) Common peroneal (fibular) nerve
Which roots does each of the tibial nerve and common peroneal nerve originate from ?
Tibial- L4-S3
Common peroneal- L4-S2
Where does the tibial nerve pass after branching out from the sciatic nerve ?
Descends in the popliteal fossa and posterior leg to the foot, passing posteriorly and inferiorly to the medial malleolus sending out branches along the way.
What does the tibial nerve supply ?
Posterior compartment muscles of leg
Skin of posterolateral leg, sole of foot and lateral foot.
What are the terminal branches of the tibial nerve called ?
Lateral and medial plantar nerves
Where does the common peoneal (fibular) nerve pass after branching out from the sciatic nerve ?
Descends laterally in the popliteal fossa towards the lateral compartment of the leg, before branching.
What does the common peroneal (fibular) nerve supply ?
Short head of biceps and muscles in anterior and lateral compartments of the leg
Skin of upper lateral leg, lower posterolateral leg, anterolateral leg and dorsum of foot.
What are the terminal branches of the common peroneal (fibular) nerve called ?
Deep and superficial peroneal [fibular] nerves
