Brachial plexus

Question 1

How is the brachial plexus formed?

Answer 1

From ANTERIOR rami of C5-C8 and T1 nerves
Roots, Trunks, Divisions, Cords, Branches (medial >lateral)
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Question 2

Roots (5)

Answer 2

1. C5
2. C6
3. C7
4. C8
5. T1
   - Pass through gap between ANTERIOR and MIDDLE scalene, with subclavian A
   - Sympathetic fibres carried by each root received from gray rami of middle+inferior cervical ganglion as roots pass scalene muscles

Question 3

Trunks (3)

Answer 3

1. Superior- union of C5+C6
2. Middle- continuation of C7
3. Inferior- Union of C8+ T1
   - Divide into ANTERIOR and POSTERIOR divisions as plexus passes through CERVICOAXILLARY canal, posterior to clavicle

Question 4

Divisions ( 6- 3 ant, 3 post)

Answer 4

Posterior

1. Lateral
2. Posterior
3. Medial
   - supply POSTERIOR (EXTENSOR) compartments

Anterior

1. Superior
2. Middle
3. Inferior
   - supply ANTERIOR (FLEXOR) compartments

Formed as plexus passes through CA canal, posterior to clavicle

Question 5

Cords (3)

Answer 5

1. Lateral- Anterior divisions of superior and middle trunk
2. Medial- Anterior divisions of inferior trunk
3. Posterior- Posterior divisions of all 3 trunks
   * Bear relationship to 2nd part of axillary artery that is indicated by nerves- lateral cord is LATERAL to axillary artery etc

Question 6

Branches (5)

Answer 6

1. Musculocutaneous nerve (C5,C6,C7)
2. Median nerve (C6- T1)
3. Ulnar nerve (C5-T1)
4. Axillary nerve (C5, C6)
5. Radial nerve (Roots C5-T1)

• Peripheral nerves (product of plexus formation)

Question 7

Musculocutaneous nerve motor and sensory function

Answer 7

Motor- Flexor compartment of arm ( biceps brachii, brachialis and coracobrachialis)
Sensory- Lateral aspect of forearm (lat. cutaneous branch forearm, which innervates lat half of ant. forearm and small portion of post. forearm)

Question 8

Median nerve motor and sensory function

Answer 8

Motor- Flexor muscles of forearm, thenar muscles and 2 lateral lumbricals
Sensory- Lateral aspect of palm (through palmar cutaneous branch) , lateral 3.5 fingers on palmar surface (digital cutaneous branch)

Question 9

Ulnar nerve motor and sensory function

Answer 9

Motor- Muscles of hand bar thenar and 2 lat. lumbricals, flexor carpi ulnaris and medial half of flexor digitorum profundus
Sensory- Anterior/ posterior surfaces of medial 1.5 fingers and associated palm area

Question 10

Axillary nerve motor and sensory function

Answer 10

Motor- Deltoid and teres minor

Sensory- Skin and regimental patch (inferior deltoid) through superior lateral cutaneous nerve

Question 11

Radial nerve motor and sensory function

Answer 11

Motor- Posterior compartment of arm/forearm

Sensory- Skin in posterior arm/forearm, posterior and lateral asprct of hand dorsum

Question 12

What is the supraclavicular branch of the brachial plexus?

Answer 12

Dividied into SUPRACLAVICULAR and INFRACLAVICULAR by clavicle
4 branches of supraclavicular part of plexus arise from roots and trunks of BP
1. Dorsal scapular n (root)
2. Long thoracic n (root)
3. Nerve to subclavius (trunk)
4. Suprascapular n (trunk)
All approachable through neck
5 unnamed muscular branches arise from all 5 roots of plexus which supply scalenes+ longus colli muscles.
C5 root of phrenic nerve (branch of cervical plexus) arises from C5 plexus root, joins C3-C4 components on ant. surface of ant. scalene.

Question 13

What is the infraclavicular branch of the brachial plexus?

Answer 13

1. Lateral pectoral n (lateral cord)
2. Medial pectoral n (medial cord)
3. Medial cutaneous n of arm (medial cord)
4. Medial cutaneous n of forearm (medial cord)
5. Superior subscapular n (posterior cord)
6. Thoracodorsal n (posterior cord)
7. Inferior subscapular n (posterior cord)