The brachial plexus is formed by the spinal nerves C5-T1 and divides into supraclavicular and infraclavicular parts. It gives rise to branches that innervate muscles and skin in the upper limb. In the forearm, the median nerve innervates flexor muscles and thenar muscles, and the radial and ulnar nerves innervate extensor muscles. Compression of the median nerve can cause carpal tunnel syndrome.

1. The brachial plexus

2. The brachial plexus
• The brachial plexus is
formed by the spinal
nerves C5, C6, C7,
C8 and Th1.

3. The brachial plexus
is divided into 2 parts ;
supraclavicular and
infraclavicular part.

4. Supraclavicular part
It appear as the three trunks
that passes between the
anterior and middle scalene
muscle .
The trunks are the superior
trunk, the middle trunk and the
inferior trunk.

5. Anatomical Relationships
The scalene muscles are an important part of the anatomy of the neck, with several
important structures located between and around them.

6. Infraclavicular part
• It is the part situated within the
axillary fossa where the trunks
regroup into cords that surround
the brachial artery .
• The cords are as follow –
1. The lateral cord
2. The medial cord
3. The posterior cord

7. RTDCB
• Brachial plexus comprises of Root, Trunk,
Division, Cord and peripheral Branches.
• A mnemonic for remember the region of
the
brachial plexus is:
• Real - Roots
• Teenagers - Trunks
• Drink - Divisions
• Cold - Cords
• Beer – Branches

8. Trunks
At the base of the neck, the
roots of the brachial plexus
converge, forming three trunks.
These structures are named by
their anatomical position:
Superior trunk: A combination
of C5 and C6 roots.
Middle trunk: A continuation of
C7.
Inferior trunk: A combination
of C8 and T1 roots.
The trunks begin to move
laterally, crossing the posterior
triangle of the neck.

10. Minor Branches
In addition to the five major branches of the brachial plexus, there are a number of smaller nerves that arise. They do so
from all five parts of the brachial plexus, and are listed below:
Roots Trunks Lateral cord Medial cord Posterior cord
Dorsal scapular
nerve
Long thoracic
nerve
Suprascapular
nerve
Nerve to
subclavius
Lateral pectoral
nerve
Medial pectoral
nerve
Medial
cutaneous nerve
of arm
Medial
cutaneous nerve
of forearm
Superior
subscapular
nerve
Thoracodorsal
nerve
Inferior
subscapular
nerve

11. Branches of Supraclavicular part
It gives 8 short branches-
Branch Supply
The dorsal scapular
nerve
Levator scapulae and
rhomboid muscles
The long thoracic nerve Serratus anterior
The suprascapular nerve Supraspinous and
infraspinous fossae
The subclavian nerve Subclavius muscle
The lateral and medial
pectoral nerves
Pectoralis major and
pectoralis minor
The subscapular nerve Subscapularis and teres
major
The thoracodorsal nerve Latissimus dorsi
The axillary nerve Deltoid and teres major

13. The quadrangular space is a gap in the muscles of the posterior
scapular region. It is a pathway for neurovascular structures to
move from the axilla to the posterior shoulder and arm.
Its boundaries are:
Superior – Subscapularis and teres minor.
Inferior – Teres major.
Laterally – Surgical neck of humerus.
Medially – Long head of triceps brachii.
The axillary nerve and posterior circumflex humeral artery pass
through the quadrangular space.
The axillary nerve is the greatest of the short branches. It arises
from the posterior cord and proceeds to the quadrangular
foramen. Further it loops around the surgical neck of humerus
and reaches the posterior surface of shoulder,

14. Long branches of brachial plexus
The cords of the infraclavicular part give rise to the long branches-
• The musculocutaneous nerve- it arises from the lateral cord
and then transverses the coracobrachialis and appears in between
the biceps brachii and the brachialis. It terminates within the skin
of anterolateral area of forearm.
Motor Functions
The musculocutaneous nerve innervates:
• biceps brachii
• brachialis
• coracobrachialis.
Sensory Functions
The musculocutaneous nerve gives rise to the lateral cutaneous
nerve of forearm.
The lateral cutaneous nerve of forearm innervates the skin of the
lateral aspect of the forearm.

15. The medial cutaneous nerve of arm- it
arises from the medial cord and terminates within
the skin of the medial area of arm
.
The medial cutaneous nerve of forearm-
it arises from the medial cord and terminates within
the skin of the anteromedial area of forearm.

16. The median nerve is a major peripheral
nerve of the upper limb. is derived from the medial and
lateral cords of the brachial plexus.
Nerve roots: C6 – T1.
In the forearm, the nerve travels between the flexor
digitorum profundus and flexor digitorum superficialis
muscles.
Motor functions: Innervates the flexor muscles in the
anterior compartment of the forearm (except the flexor
carpi ulnaris and a half part of the flexor digitorum
profundus, innervated by the ulnar nerve). Also supplies
innervation to the thenar muscles and lateral two lumbricals
in the hand.
Sensory functions: Gives rise to the palmar cutaneous
branch, which innervates the lateral part of the palm, and
the digital cutaneous branch, -innervates the lateral three
and a half fingers on the anterior (palmar) surface of the
hand.

17. Sensory Functions
The median nerve is responsible for the
cutaneous innervation of part of the hand.
This is achieved via two branches:
• Palmar cutaneous branch – Arises
in the forearm and travels into the hand. It
innervates the lateral aspect of the palm. This
nerve does not pass through the carpal
tunnel, and is spared in carpal tunnel
syndrome.
• Palmar digital cutaneous branch –
Arises in the hand. Innervates the palmar
surface and fingertips of the lateral three and
half digits.

18. The median nerve (C5-T1).
Тhe median nerve descends down the arm, initially lateral to
the brachial artery and becomes situated medially.
The median nerve enters the anterior compartment of the
forearm via the cubital fossa.
In the forearm, the nerve travels between the flexor digitorum
profundus and flexor digitorum superficialis muscles. The
median nerve gives rise to two major branches in the forearm:
• Anterior interosseous nerve – Supplies the deep
muscles in the anterior forearm.
• Palmar cutaneous nerve – Innervates the skin of the
lateral palm.
The median nerve enters the hand via the carpal tunnel,
where it terminates by dividing into two branches:
• Recurrent branch – Innervates the thenar muscles.
• Palmar digital branch – Innervates the palmar
surface and fingertips of the lateral three and half digits. Also
innervates the lateral two lumbrical muscles.

19. Motor Functions
The median nerve innervates the majority of the muscles in the
anterior forearm, and some intrinsic hand muscles.
The Anterior Forearm
In the forearm, the median nerve directly innervates muscles in the
superficial and intermediate layers:
• Superficial layer: Pronator teres, flexor carpi radialis and
palmaris longus.
• Intermediate layer: Flexor digitorum superficialis.
The median nerve also gives rise to the anterior interosseous nerve,
which supplies the deep flexors:
• Deep layer: Flexor pollicis longus, pronator quadratus, and
the lateral half of the flexor digitorum profundus (the medial half of the
muscle is innervated by the ulnar nerve).
In general, these muscles perform pronation of the forearm, flexion of
the wrist and flexion of the digits of the hand.
The Hand
The median nerve: the recurrent branch of the median nerve
innervates the thenar muscles – muscles associated with movements
of the thumb.
The palmar digital branch innervates the lateral two lumbricals – these
muscles perform flexion at the metacarpophalangeal joints of the
index and middle fingers
The remaining muscles in the anterior forearm and hand are innervated by the ulnar nerve).

20. Compression of the median nerve within the carpal
tunnel can cause carpal tunnel syndrome (CTS). It is
the most common mononeuropathy and can be
caused by thickened ligaments and tendon sheaths.
Its aetiology is, however, most often idiopathic. If left
untreated, CTS can cause weakness and atrophy of
the thenarmuscles.
Clinical features include numbness, tingling and pain
in the distribution of the median nerve. The pain will
usually radiate to the forearm. Symptoms are often
associated with waking the patient from their sleep
and being worse in the mornings.
Tests for CTS can be performed during physical
examination:
• Tapping the nerve in the carpal tunnel to elicit
pain in median nerve distribution (Tinel’s Sign)
• Holding the wrist in flexion for 60 seconds to
elicit numbness/pain in median nerve distribution
(Phalen’s manoeuvre).
Fig 2 – Thenar muscle wasting, secondary to
carpal tunnel syndrome.

21. The radial nerve
• The radial nerve is a major peripheral nerve of the upper limb.
• Nerve roots: C5-T1.
• Sensory: Innervates most of the skin of the posterior side of forearm,
and the dorsal surface of the lateral side of the palm, and lateral three
and a half digits.
• Motor: Innervates the triceps brachii (extends at the elbow), and the
majority of the extensor muscles in the forearm (extends the wrist and
fingers and supinates the forearm).
• The radial nerve is a continuation of the posterior cord of the brachial
plexus. It therefore contains fibers from nerve roots C5 – T1.

22. Fig. – View of the posterior arm, showing the
anatomical course of the radial nerve
The nerve arises in the axilla region, where it is situated
posteriorly to the axillary artery. It exits the axilla inferiorly
(via the triangular interval), and supplies branches to the
long and medial heads of the triceps brachii.
The radial nerve then descends down the arm, travelling
in a shallow depression within the surface of the humerus
– known as the radial groove.
As it descends, the radial nerve wraps around the
humerus laterally, and supplies a branch to the lateral
head of the triceps brachii. During much of its course
within the upper arm, it is accompanied by the deep
branch of the brachial artery.
To enter the forearm, the radial nerve moves anteriorly
over the lateral epicondyle of the humerus, through the
cubital fossa. The nerve then terminates by dividing into
two branches:
• Deep branch (motor) – innervates most of the
muscles in the posterior compartment of the forearm.
• Superficial branch (sensory) – contributes to
the cutaneous innervation of the hand and fingers

24. Motor Functions
The radial nerve innervates the muscles located in the posterior upper arm and posterior forearm.
In the upper arm, it innervates the three heads of the triceps brachii – which acts to extend the arm at the
elbow.
The radial nerve also gives rise to branches that supply the brachioradialis and extensor carpi radialis longus
(muscles of the posterior forearm).
A terminal branch of the radial nerve, the deep branch, innervates the remaining muscles of the posterior
forearm. As a generalisation, these muscles act to extend at the wrist and finger joints, and supinate the
forearm.
Note: When the deep branch of the radial nerve penetrates the supinator muscle of the forearm, it is termed
the posterior interosseous nerve for the remainder of its course.
The deep branch of the
radial nerve pierces the
supinator muscle, and
becomes the posterior
interosseous nerve

25. Sensory Functions
There are four branches of the radial nerve that provide
cutaneous innervation to the skin of the upper limb.
Three of these branches arise in the upper arm:
• Lower lateral cutaneous nerve of arm –
Innervates the lateral aspect of the upper arm, below the
deltoid muscle.
• Posterior cutaneous nerve of arm – Innervates
the posterior surface of the upper arm.
• Posterior cutaneous nerve of forearm –
Innervates a strip of skin down the middle of the
posterior forearm.
The fourth branch – the superficial branch – is a terminal
division of the radial nerve. It innervates the dorsal
surface of the lateral three and half digits, and their
associated palm area.
The cutaneous innervation of the radial nerve

26. In the Radial Groove
The radial nerve is tightly bound within the spiral groove of the humerus. Thus, it is most susceptible to damage
with a fracture of the humeral shaft.
• Motor functions
o The triceps brachii may be weakened, but is not paralysed (branches to the long and medial heads of the
triceps arise proximal to the radial groove).
o Muscles of the posterior forearm are affected. The patient is unable to extend at the wrist and fingers.
Unopposed flexion of wrist occurs, known as wrist-drop.
• Sensory functions – the cutaneous branches to the arm and forearm have already arisen. The superficial
branch of the radial nerve will be damaged, resulting in sensory loss on the dorsal surface of the lateral three and
half digits, and their associated palm area.
In the Axilla
The radial nerve can be damaged in the axilla region by a dislocation at the shoulder joint, or a fracture
of the proximal humerus. Occasionally, it is injured via excessive pressure on the nerve within the axilla
(e.g. a badly fitting crutch).
• Motor functions – the triceps brachii and muscles in posterior compartment are affected. The
patient is unable to extend at the forearm, wrist and fingers. Unopposed flexion of wrist occurs, known
as wrist-drop.
• Sensory functions – all four cutaneous branches of the radial nerve are affected. There will be
a loss of sensation over the lateral and posterior upper arm, posterior forearm, and dorsal surface of the
lateral three and a half digits.

27. Superficial Branch Deep Branch
Mechanism Stabbing or laceration of
forearm
Fracture of radial head,
or posterior dislocation
of radius
Motor functions None Majority of the muscles
in posterior forearm are
affected. Wrist-drop
does not occur, as the
extensor carpi radialis
longus is unaffected, and
maintains some
extension at the wrist
Sensory functions Sensory loss affecting
the lateral 3 ½ digits, and
associated palm area
None
In the Forearm
There are two terminal branches of the radial nerve located within the forearm:

28. The ulnar nerve is a major peripheral nerve of the
upper limb.
Spinal roots: C8-T1.
Motor functions: Innervates the muscles of the hand
(apart from the thenar muscles and two lateral
lumbricals), flexor carpi ulnaris and medial half of flexor
digitorum profundus.
Sensory functions: Innervates the anterior and posterior
surfaces of the medial one and half fingers, and the
associated palm area.
The ulnar nerve

30. The ulnar nerve is derived from the brachial plexus. It is a
continuation of the medial cord, containing fibres from
spinal roots C8 and T1.
After arising from the brachial plexus, the ulnar nerve
descends down the medial side of the upper arm. At the
elbow, it passes posterior to the medial epicondyle of the
humerus, entering the forearm. At the medial epicondyle,
the nerve is easily palpable and vulnerable to injury.
In the forearm, the ulnar nerve pierces the two heads of
the flexor carpi ulnaris, and travels alongside the ulna.
Three branches arise in the forearm:
• Muscular branch: innervates some muscles in the
anterior compartment of the forearm.
• Palmar cutaneous branch: innervates the skin of
the medial half of the palm.
• Dorsal cutaneous branch: innervates the skin of
the medial 1 and 1/2 fingers, and the associated palm
area.
At the wrist, the ulnar nerve travels superficially to the
flexor retinaculum. It enters the hand via the ulnar canal
(or Guyon’s canal). In the hand the nerve terminates by
giving rise to superficial and deep branches.

31. Motor Functions
The ulnar nerve innervates muscles in the anterior
compartment of the forearm, and in the hand.
The Anterior Forearm
In the anterior forearm, the muscular branch of the
ulnar nerve supplies two muscles:
• Flexor carpi ulnaris – Flexes and adducts the
hand at the wrist.
• Flexor digitorum profundus (medial half) –
Flexes the fingers.
The remaining muscles in the anterior forearm are
innervated by the median nerve.

32. The Hand
The majority of the intrinsic hand muscles are innervated by
the deep branch of the ulnar nerve.
The hypothenar muscles (a group of muscles associated with
the little finger) are innervated by the ulnar nerve. It also
innervates some other muscles of the hand:
• Medial two lumbricals
• Adductor pollicis
• Interossei of the hand
• Palmaris brevis
The other muscles in the hand (such as the thenar eminence)
are innervated by the median nerve

33. Sensory Functions
There are three branches of the ulnar nerve that are responsible for its cutaneous innervation.
Two of these branches arise in the forearm, and travel into the hand:
• Palmar cutaneous branch: Innervates the skin of the medial half of the palm.
• Dorsal cutaneous branch: Innervates the skin of the medial one and a half fingers, and the associated
dorsal hand area.
The last branch arises in the hand itself:
• Superficial branch – Innervates the palmar surface of the medial one and a half fingers.