The Brachial Plexus
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The
axilla | Main Anatomy
Index | Nerves of the upper limb
Last updated 30 March 2006
The Brachial Plexus (pp.
512-22)
- The brachial plexus is a large and very important plexus
of nerves.
- It is situated partly in the neck and partly in the axilla.
- The supraclavicular part
(rami and trunks with their branches) of the brachial
plexus is in the posterior
triangle of the neck, and its infraclavicular
part (cords and their branches) is in the axilla.
- The brachial plexus is formed by the union
of the ventral rami of nerves C5 to C8 and the
greater part of T1 ventral ramus.
- The rami that form the brachial plexus are often referred
to as the "roots of the
brachial plexus".
- They lie between the scalenus
anterior and scalenus medius
muscles.
Plan
of the Brachial Plexus
Click here for a
schematic of the plan of the brachial plexus (roots to cords).
Click here for a
schematic of the cords of the brachial plexus and their terminal
branches.
- The ventral rami from C5 and C6
unite to form the superior (upper)
trunk.
- C7 continues as the middle trunk.
- C8 and T1 unite to form
the inferior (lower) trunk.
- Each of the 3 trunks divides into anterior
and posterior divisions, posterior to the
clavicle.
- These divisions are of fundamental significance as the anterior division supply anterior
(flexor) parts and the posterior
division supply posterior (extensor) parts of
the upper limb.
- The 3 posterior divisions
unite to form the posterior cord.
- The anterior divisions of the
superior and middle trunks unite to form the lateral cord.
- The anterior division of the
inferior trunk continues as the medial cord.
- The cords of the brachial plexus bear their name in
relation to their position to the axillary artery.
Branches of the Brachial Plexus
Supraclavicular Branches of the Brachial
Plexus
The
Dorsal Scapular Nerve
- This is formed at the posterior aspect of the ventral
ramus of C5 with
frequent contributions from C4.
- It pieces the scalenus medius
muscle, and runs deep to the levator
scapulae muscle, which it helps to supply.
- It then enters the deep surface of the rhomboid
muscles, which it supplies.
The Long
Thoracic Nerve
The
nerve to the Subclavius Muscle
- This nerve is from the anterior aspect of the superior trunk, from C5, with occasional additions
from C4 and C6.
- It descends posterior to the clavicle and anterior to
the brachial plexus to supply the subclavius
muscle.
The
Suprascapular Nerve
Infraclavicular Branches of the Brachial
Plexus
- These arise from the cords of the plexus and are
approachable though the axilla.
Branches
of the Lateral Cord
The
Lateral Pectoral Nerve
The
Musculocutaneous Nerve
- This nerve supplies the muscles of the anterior aspect of
the arm.
- Just proximal to the elbow
joint, the musculocutaneous nerve pierces the deep
fascia and becomes superficial.
- From here it is known as the lateral
antebrachial cutaneous nerve (lateral
cutaneous nerve of the forearm) and it supplies the skin
on the lateral aspect of the forearm.
Lateral
Root of the Median Nerve
Click here to go to the
median nerve entry under Nerves of the Upper Limb.
Branches
of the Medial Cord
- The medial cord of the brachial plexus has 5 branches; three side
branches and two terminal branches.
The
Medial Pectoral Nerve
Medial Brachial Cutaneous Nerve
- This nerve supplies the skin over the medial surface of
the arm and the proximal part of the forearm.
- It usually communicates with the intercostobrachial
nerve, which supplies the skin of the floor of
the axilla and adjacent areas.
The Medial Antebrachial Cutaneous Nerve
- This nerve runs between the axillary artery and
vein to supply
the skin over the medial surface of the forearm.
The Ulnar Nerve
Click here to go to the
ulnar nerve entry under Nerves of the Upper Limb.
- The ulnar nerve passes through the arm into the forearm
and hand, where it supplies one and one-half muscles in
the forearm, most small muscles in the hand,
and some skin.
The
Medial Root of the Median Nerve
Click here to go to the
median nerve entry under the Nerves of the Upper Limb.
Branches
of the Posterior Cord
- The posterior cord of the brachial plexus has 5 branches; three side
branches and two terminal branches.
- Generally, these nerves supply muscles that extend the joints of the upper limb.
- These branches also supply cutaneous nerves of the
extensor surface of the upper limb.
The
Upper Subscapular Nerve
The
Thoracodorsal Nerve
The
Lower Subscapular Nerve
The Axillary
Nerve
Click here to go to the
axillary nerve entry under Nerves of the Upper Limb.
The Radial Nerve
Click here to go to the
radial nerve entry under Nerves of the Upper Limb.
- This nerve provides the major nerve supply to the
extensor muscles of the upper limb.
- It also supplies cutaneous sensations to the skin to the
extensor region, including the hand.
- As it leaves the axilla, the
radial nerve runs posteriorly, inferiorly, and laterally
between the long and medial heads of the triceps brachii
muscle and enter the radial
groove in the humerus.
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