All posterior cord branch innervates the muscles of the posterior axillary wall except the radial nerve
Axillary nerve is accompanied by the posterior circumflex humeral artery
Therefore fracture or obstruction of the humerus at the levels of this areas could be dangerous to the related nerves.
OF THE PLEXUS
BRANCHES OF THE PLEXUS
VARIATIONS IN THE FORMATION
OF THE PLEXUS
RELATIONSHIPS OF SOME
BRACHIAL NERVES TO BONES
APPLIED ANATOMY OF THE
The brachial plexus is a network of nerves
that is responsible for the cutaneous and
muscular innervations of the entire upper
limb with two exceptions;
The trapezius muscle which is innervated by
the SPINAL ACCESSORY NERVE and
An area close to the axilla which is
innervated by the
• The brachial plexus begins in the
neck extending through the axillary
inlet into the axilla where almost all
the branches of the plexus arises
after it has crossed the first rib.
ARRANGEMENT/FORMATION OF THE
• The brachial plexus is formed by the union
of the ventral rami of the lower four
cervical nerves (C5-C8) and the greater
part of the ventral ramus of the first
thoracic nerve (T1) forming the roots of
• These roots passes through the gap
between the anterior and middle scalene
muscles with the subclavian artery.
• The roots unite to form the 3 trunks at the
inferior border of the neck viz;
• Superior trunk- formed by the union of C5 &
C6 at the lateral border of the scalenus medius
• Middle trunk- formed as a continuation of C7
• Inferior trunk- formed from the union of C8
& T1 posterior to the scalenius anterior
• the three trunks incline laterally, and either just
behind or above the clavicle each divides into
an anterior and a posterior division.
• The anterior division will supply the
anterior compartments of the upper limb
while the posterior division supplies the
extensor compartment of the upper limb.
• The six (6) divisions of the brachial
plexus unite to form the three cords;
• The lateral cord; formed by the union of
the anterior divisions of the superior and
• Medial cord; formed as a continuation of
the anterior division of the inferior trunk.
• Posterior cord; formed by the union of
the posterior divisions of the three trunks.
• The cords of the plexus bear the
relationship to the second part of the
axillary artery that is indicated by their
• The lateral cord is lateral to the axillary
artery, the medial cord is medial to it
while the posterior is posterior to it.
Branches of the plexus
• Branches are described as supraclavicular and
• The supraclavicular branches arises from the
roots and trunks and are approachable
through the neck.
• Supraclavicular branches;
1. Long Thoracic Nerve (C5-C7)- passes
through the cervicoaxillary canal and
posterior to other BP components to supply
the serratus anterior muscle.
2. Dorsal Scapular nerve (C5)- pierces the
middle scalene muscle and runs deep to supply
the levator scapulae, enters the deep surface
of the Rhomboids muscle supplying it.
3. Suprascapular Nerve (C5-6)- passes
laterally through the posterior triangle of the
neck and through the suprascapular foramen
to enter the posterior scapular region;
supplies the supraspinatus, infraspinatus
muscles and glenohumeral joint.
• 4. Nerve to Subclavius (C5-6)- originates
from the superior trunk of the brachial plexus;
• passes anteroinferiorly over the subclavian
artery and vein;
• innervates the subclavius muscle.
• Infraclavicular branches of the plexus;
• Lateral cord
5. Lateral Pectoral Nerve (C5-7)- is the most
proximal of the branches from the lateral
cord, passes anteriorly, together with the
thoraco-acromial artery, to penetrate the
clavipectoral fascia that spans the gap
between the subclavius and pectoralis minor
It innervtes the pectorialis major muscle.
6. Musculocutaneous Nerve (C5-7)- is a large terminal
branch of the lateral cord, passes laterally to penetrate
the coracobrachialis muscle and pass between the
biceps brachii and brachialis muscles in the arm, and
innervates all three flexor muscles in the anterior
compartment of the arm.
innervates the coracobrachialis muscle, biceps brachii
and brachialis muscles.
It therefore supplies the anterior compartment
muscles of the arm continuing as the lateral cutaneous
nerve of the forearm.
7. Lateral Root of Median nerve (C5-7)- is the
largest terminal branch of the lateral cord and
passes medially to join a similar branch from the
medial cord to form the median nerve.
• Medial cord
• 8. Medial Root of Median Nerve (C8-T1)- it joins
the lateral roots from the lateral cord to form the
median nerve (C5-T1).
• The median nerve is formed anterior to the third
part of the axillary artery by the union of lateral
and medial roots originating from the lateral and
medial cords of the brachial plexus.
• It passes into the arm anterior to the brachial
artery, through the arm into the forearm
where branches innervate most of the
muscles in the anterior compartment of the
forearm (except for the flexor carpi ulnaris
muscle and the medial half of the flexor
digitorum profundus muscle, which are
innervated by the ulnar nerve).
• The median nerve continues into the hand to
• the three thenar muscles associated with the
• the two lateral lumbrical muscles associated with
movement of the index and middle fingers;
• the skin over the palmar surface of the lateral
three and one-half digits and over the lateral side
of the palm and middle of the wrist.
9. Medial Pectoral Nerve (C8-T1)- receives a
communicating branch from the lateral pectoral nerve
and then passes anteriorly between the axillary artery
and axillary vein.
innervates the pectorialis minor muscle and part of the
pectorialis major muscle too.
10. Medial Cutaneous Nerve of the arm (C8-T1)- supplies
the skin of the medial side of the arm and superior
part of the forearm and also the floor of the axilla.
11. Medial cutaneous Nerve of the Forearm (C8-T1)innervates the skin on the medial side of the forearm.
Known as the “fools nerve”.
12. Ulnar Nerve (C8-T1)- is a large terminal branch of the
Transverse the arm into the forearm without branching.
innervates one and a half muscles in the anterior
compartment of the forearm (flexor carpi ulnaris,
flexor digitorum profundus).
innervates also all the intrinsic muscles of the hand
except (3 thernar muscles and 2 lumbricals).
It innervates skin over the palmar surface of the little
finger, medial half of the ring finger, and associated
palm and wrist, and the skin over the dorsal surface of
the medial part of the hand.
• Posterior cord
13. Upper Subscapular (C5-6)- is short, passes
into the subscapularis muscle innervating it.
14. Thoracodorsal Nerve (C6-8)- the longest of
the 3 side branches of the posterior cord, it
passes vertically along the posterior axillary
wall and innervates latissimus dorsi.
15. Lower Subscapular Nerve (C5-6)- inervates
the teres major muscle as well as the inferior
part of the subscapularis muscle.
16. Axillary Nerve (C5-6)- a terminal branch of
the posterior cord, passes inferiorly and
laterally along the posterior wall of the axilla
to exit the axilla through the quadrangular
It passes posteriorly around the surgical neck
of the humerus.
innervates the teres minor and the deltoid
17. Radial Nerve (C5-8, T1)- is the largest terminal branch
of the posterior cord.
The largest branch of the brachial plexus.
It passes out of the axilla and into the posterior
compartment of the arm by passing through the
triangular interval between the inferior border of the
teres major muscle, the long head of the triceps brachii
muscle, and the shaft of the humerus.
It is accompanied through the triangular interval by the
profunda brachii artery, which originates from the
brachial artery in the anterior compartment of the
Supplies all the extensor muscles of the posterior
compartment of the upper limb.
Skin on the posterior aspect of the arm and forearm.
VARIATIONS IN THE FORMATION OF THE
• Variations in the formations of the
brachial plexus are common.
• In addition to the five (5) ventral rami
(C5-8) and T1 that form the roots of the
brachial plexus, small contributions may
be made by the ventral ramus of C4 or
• When the contribution from C4 is more
than that of T1, the root of the plexus
starts from C4 and ends at C8.
• This type of brachial plexus is termed
• When the contribution from T2 is more
and the superior root is C6, it is termed
Variation may also occur in the;
Formation of trunks, division and cords.
Origin and or contribution of branches.
Relation to axillary artery and scalene
• In some individuals, trunk divisions or
cord formations may be absent in one or
other parts of the plexus; however the
make up of the terminal branches remain
RELATIONSHIPS OF SOME
BRACHIAL NERVES TO BONES
1. Surgical neck of humerus; The Axillary Nerve,
which supplies the teres minor and deltoid
muscle, a major abductor of the humerus at
the shoulder joint.
2. Radial groove; Radial Nerve, which supplies
all the extensor muscles of the upper limb.
3. Medial epicondyle; Ulnar Nerve which
supplies medial one and half part of the hand
and the anterior compartment of the
CLINICAL AND APPLIED
ANATOMY OF BRACHIAL
• The brachial plexus is an extremely
• When damaged, it requires meticulous
clinical history taking and examination.
• Brachial plexus injuries are important
because they affect movements and
cutaneus sensations in the upper limb.
• Diseases, stretching and wounds in the
posterior triangle of the neck or in the axilla
may produce brachial plexus injuries.
• Signs and symptoms of the injuries depends on
the side of the plexus that is involved.
• Injuries to superior parts of the brachial
plexus (C5 and C6).
• Usually result from an excessive increase in
the angle between the neck and the shoulder.
• These injuries can occur in a person who is
thrown from a motorcycle or a horse and lands
on the shoulder in a way that widely separates
the neck and shoulder.
• Injury to the superior trunk of the plexus is
apparent by the characteristic position of the
limb ("waiter's tip position"), in which the limb
hangs by the side in medial rotation.
• Upper brachial plexus injuries can also occur in a
newborn when excessive stretching of the neck
occurs during delivery.
• Various terms are used to describe superior
brachial plexus injuries;
• Erb palsy (paralysis), Erb- Duchenne palsy
(paralysis), Duchenne-Erb palsy (paralysis), and
upper radicular syndrome.
• The inferior parts of the brachial plexus may
also be injured during a breech birth when the
infant’s limb are pulled over the head.
• These events injure the inferior trunk of the
brachial plexus (C8-T1) and may pull the
dorsal and ventral roots of the spinal nerves
from the spinal cord.
• The short muscles of the hand are affected,
and a claw hand results.