Summary Upper Limb - Brachial Plexus

(C4) C5-C8 + T1 (T2) supply the upper limb Here roots of C5-C6 unite to form upper trunk;

Roots of C7 continues as middle trunk;

Roots of C8-T1 form lower trunk




The five roots of the brachial plexus are the five
anterior rami of the spinal nerves, (C4) C5-T1 (T2) The 3 trunks emerge from between scaleni and pass
after they have given off any segmental supply to the downwards and laterally across 1st rib. At lateral
scaleni muscles of the neck border of 1st rib behind clavicle, each trunk divides
into anterior and posterior divisions which stream
1. Scalenus anterior: anterior primary rami of into axilla and unite into three cords:
C5-C7 (BP)
2. Scalenus medius: anterior primary rami of 1. Lateral cord – anterior divisions of
C3-C8 (CP/BP) (form cervical plexus C1-C4) upper/middle trunks
3. Scalenus posterior: anterior primary rami of 2. Medial cord – continuation of anterior
C7-C8 (BP) division of lower trunk
4. Scalenus minimus: anterior primary rami of 3. Posterior cord – posterior divisions of all 3
C7-C8 (BP) trunks

At first:

- Medial cord lies posterior to axillary artery
The roots of the BP are formed by the anterior - Posterior and lateral cords lie lateral to artery
primary rami (ventral) of C5-C8 plus T1 (pre-fixed = + - Behind pectoralis
C4 & post-fixed = + T2). minor (2nd part of
artery)
The roots become sandwiched between scalenus
anterior and scalenus medius (above the 2nd part of Note: Roots – Trunks –
subclavian artery) Divisions – Cords - Branches

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, (Anterior primary rami after segment branches).

* Receives GR from Cx. Ʃ chain

- C5, C6 – MCG
- C7, C8 – ICG
- T1 from T1 ganglion

1. Dorsal scapular nerve (C5) levator scapular
and rhomboids
2. Long thoracic nerve (C5, C6, C7) serratus
anterior
Individual nerve damage:

- Musculocutaneous nerve
3. Nerve to subclavius (C5, C6) - Axillary nerve
4. Suprascapular nerve (C5, C6) supraspinatus - Median nerve
- Radial nerve
and shoulder joint
- Ulnar nerve

Brachial plexus injuries:

- Upper BP injuries
- Lower BP injuries
- Long thoracic nerve

Results of nerve injury: the consequences of the injury
to a nerve depends on the exact site and the severity
of the injury



Lateral cord (anterior divisions of upper/middle Nerve roots: C5 – C7
trunks)
Motor functions: innervates the muscles in the
a. Lateral pectoral (C5, C6, C7) anterior compartment of the arm – biceps brachii,
b. Musculocutaneous (C5, C6, C7) brachialis and coracobrachialis (BBC). These muscles
c. Lateral root of median nerve (C6, C7) flex the upper arm at het shoulder and the elbow. In
addition, the biceps brachii also supinates the
Median cord (anterior division of lower trunk)
forearm.
d. Medial pectoral (C8, T1)
Sensory functions: gives rise to the lateral cutaneous
e. Medial cutaneous nerve of arm (C8, T1)
nerve of forearm, which innervates skin on the lateral
f. Medial cutaneous nerve of forearm (C8, T1)
surface of the forearm
g. Medial root of median nerve (C8, T1)
h. Ulnar nerve (C7, C8, T1) Anatomical course: The musculocutaneous nerve
arises from the lateral cord of the brachial plexus,
Posterior cord (all posterior divisions of the 3 trunks)
After originating from the brachial plexus, the
i. Upper subscapular (C5, C6) musculocutaneous nerve leaves the axilla, and pierces
j. Thoracodorsal nerve (C6, C7, C8) the coracobrachialis muscle, near it’s the point of
k. Lower subscapular (C5, C6) insertion on the humerus.
l. Axillary nerve (C5, C6) (circumflex nerve)
m. Radia nerve (C5, C6, C7, C8, T1)