Cutaneous innervation of the arm
1. Lateral supraclavicular nerve (C3 and 4): supply
the skin over the upper half of the deltoid muscle.
2. The upper lateral cutaneous nerve of the arm is a
branch of the axillary nerve (C5 and 6) that supply
the skin over the lower half of the deltoid
3. The lower lateral cutaneous nerve of the arm is a
branch of the radial nerve (C5 and 6) that supply the
skin over the lateral surface of the arm below the
deltoid
4. The medial cutaneous nerve of the arm (T1) and
the intercostobrachial nerves (T2) supply the skin
of the armpit and the medial side of the arm
5. The posterior cutaneous nerve of the arm, a
branch of the radial nerve (C8) supply the skin of the
back of the arm.
Front
back
Fascia of the arm
• The brachial fascia is a sheath of deep fascia that
encloses the arm like a sleeve deep to the skin and
subcutaneous tissue. From it 2 intermuscular septa
pass inwards dividing the arm into anterior and
posterior compartments.
• The medial intermuscular septum extends from
the deep surface of the brachial fascia to the medial
border of the humerus and the medial supracondylar
ridge. It is pierced by the ulnar nerve at the level of
insertion of coracobrachialis.
• The lateral intermuscular septum, extend from the
deep surface of the brachial fascia to the lateral
border and the lateral supracondylar ridge of the
humerus. It is pierced by radial nerve at the junction
of the middle and lower thirds of the upper arm,.
Anterior Compartment of the Upper Arm
1. Biceps brachii muscle
• Origin: it has 2 heads:
a) Long head: from supraglenoid tubercle of
scapula
b) Short head: from the tip of coracoid process of
scapula in common with coracobrachialis
• Insertion: into the posterior part of radial
tuberosity and through the bicipital aponeurosis
into deep fascia of forearm
• Nerve Supply: Musculocutaneous nerve (C5, 6)
• Action:
• It flexes the elbow joint
• It is a powerful supinator when the elbow is
flexed
Biceps
brachii
2. Coracobrachialis
• Origin: from the tip of coracoid process of scapula
• Insertion: into the medial aspect of shaft of
humerus at its middle.
• Nerve supply: Musculocutaneous nerve C5, 6, 7
• Action: Flexes and adducts the arm
3. Brachialis
•
•
•
•
Origin: from the lower half of front of the humerus
Insertion: into front of the coronoid process of ulna
Nerve supply: Musculocutaneous nerve C5, 6, 7
Action: main flexor of the forearm
4. Brachial Artery
• Beginning: at the lower border of the teres
major muscle as a continuation of the axillary
artery.
• Course: it passes downwards and laterally
through the front of the arm where in the upper
part it lies on the medial side of the humerus
while in the lower part it lies anterior to the bone.
It ends in the cubital fossa.
• Termination: opposite the neck of the radius by
dividing into the radial and ulnar arteries.
Branches
1. Muscular branches
2. The nutrient artery to the humerus
3. The profunda brachii artery
4. The superior ulnar collateral artery arises near
the middle of the upper arm and follows the ulnar
nerve to the back of medial epicondyle.
5. The inferior ulnar collateral artery arises near
the termination of the artery. It divides into 2
branches: anterior that descends in front of medial
epicondyle and posterior branch that pierces the
medial intermuscular septum to reach the back of
medial epicondyle.
5. Musculocutaneous Nerve (C5, 6,7)
• Origin: from the lateral cord of the brachial plexus in
axilla.
• Course: It runs downward and laterally, pierces the
coracobrachialis, and then passes downward between
biceps and brachialis muscles. It appears at the lateral
margin of the biceps tendon and pierces the deep fascia
just above the elbow. It runs down the lateral aspect of
the forearm as lateral cutaneous nerve of the forearm
• Branches:
1. Muscular branches to the biceps, coracobrachialis, and
brachialis
2. lateral cutaneous nerve of the forearm supplies the
skin of the front and lateral aspects of the forearm
3. Articular branches to the elbow joint
6. Median Nerve (C5,6,7,8,T1)
• Origin: it arises by 2 roots: medial root from
the medial cord and lateral root from the
lateral cord of the brachial plexus in the
axilla.
• Course: It runs downward on the lateral side
of the brachial artery. Halfway down the
upper arm, it crosses the front of the brachial
artery and continues downward on its medial
side to the cubital fossa where it enters the
forearm.
• Branches: It has no branches in upper arm
7. Ulnar Nerve (C7,8,T1)
• Origin: from the medial cord of the brachial
plexus in the axilla.
• Course: It runs downward on the medial side of
the brachial artery as far as the middle of the
arm. At the insertion of the coracobrachialis, the
nerve pierces the medial intermuscular septum,
accompanied by the superior ulnar collateral
artery, and enters the posterior compartment of
the arm; the nerve passes behind the medial
epicondyle of the humerus.
• Branches: The ulnar nerve has no branches
in the upper arm
Posterior Compartment of Upper Arm
1. Triceps
• Origin: it has 3 heads:
1. Long head: from the infraglenoid tubercle of scapula
2. Lateral head: from a rough strip on the upper part of
posterior surface of shaft of humerus above the
spiral groove.
3. Medial head: from the lower half of posterior surface
of shaft of humerus below the spiral groove.
• Insertion: into the posterior part of the upper
surface of the olecranon process of ulna
• Nerve supply: radial nerve
• Action: Extensor of elbow joint
2. Radial Nerve (C5,6,7,8,T1)
• Origin: from the posterior cord of the brachial plexus in
the axilla.
• Course:
1. It descends behind the 3rd part of the axillary artery and
upper part of brachial artery. It leaves the front of the arm
by passing between the long and medial head of triceps.
2. It winds around the back of the arm in the spiral groove.
Here, the nerve is accompanied by the profunda brachii
vessels, and it lies directly in contact with shaft of humerus
3. It pierces the lateral intermuscular septum above the
elbow and passes infront of the arm in the interval
between brachialis and brachioradialis muscles.
• Termination: at the level of lateral epicondyle, the radial
nerve ends by dividing into 2 branches:
1. Deep branch (posterior interosseous nerve)
2. Superficial branch
• Branches
1. In the axilla:
a) branches to the long and medial heads of the triceps
b) the posterior cutaneous nerve of the arm
2. In the spiral groove:,
a) branches to the lateral and medial heads of the
triceps and to the anconeus.
b) The lower lateral cutaneous nerve of the arm
supplies the skin over the lateral and anterior aspects
of the lower part of the arm.
c) The posterior cutaneous nerve of the forearm
runs down the middle of the back of the forearm as
far as the wrist.
3. In the anterior compartment of the arm it gives:
a) branches to the brachialis, the brachioradialis, and
the extensor carpi radialis longus muscles.
b) articular branches to the elbow joint.
3. Profunda Brachii Artery
• Origin: it arises from the brachial artery near its
origin .
• Course: it accompanies the radial nerve in the
spiral groove as it passes posteriorly around the
shaft of the humerus.
• Termination: by dividing into anterior branch (radial
collateral artery) and posterior branch that
participate in the arterial anastomoses around the
elbow.
• Branches:
1. Nutrient branch that enters the humerus through the
floor of the radial groove
2. Ascending branch (deltoid branch) that anastomose
with the posterior circumflex humeral artery
3. Muscular branches to triceps
Shoulder joint
• Type: Synovial joint of ball-and-socket variety
• Articular parts:
1. head of the humerus
2. glenoid cavity of the scapula.
• Capsule: It surrounds the articular parts and is
attached medially to the margin of the glenoid
cavity outside the labrum; laterally it is attached to
the anatomic neck of the humerus. The capsule is
thin and lax, allowing a wide range of movement. It
is strengthened by the tendons of the
subscapularis, supraspinatus, infraspinatus, and
teres minor muscles (the rotator cuff muscles) and
the following ligaments:
• Ligaments:
1. The glenohumeral ligaments are three weak bands of
fibrous tissue that strengthen the front of the capsule.
2. The transverse humeral ligament strengthens the
capsule and bridges the gap between the two
tuberosities.
3. The coracohumeral ligament strengthens the capsule
above and stretches from the root of the coracoid
process to the greater tuberosity of the humerus.
4. glenoid labrum is a fibrocartilaginous rim that is attached
to the margin of the glenoid cavity and deepens it.
• Synovial membrane: lines the capsule and is attached
to the margins of the cartilage covering the articular
surfaces. It forms a tubular sheath around the tendon of
the long head of the biceps brachii. It extends through
the anterior wall of the capsule to form the subscapularis
bursa beneath the subscapularis muscle.
Movements:
• Flexion: by the anterior fibers of the deltoid, clavicular head of
pectoralis major, and coracobrachialis muscles.
• Extension: by the posterior fibers of the deltoid, teres major
muscles, latissimus dorsi and sternocostal head of pectoralis
major.
• Abduction:
1. From 0 to 15 degrees: surpaspinatus
2. From 15 to 90 degrees: middle fibers of deltoid
3. From 90 to 180 degrees: through lateral rotation of the scapula
so the glenoid cavity is directed upwards by the action of lower
fibers of trapezius and lower 5 digitations of serratus anterior
• Adduction: mainly by the pectoralis major, latissimus dorsi and
teres major muscles assisted by teres minor
• Lateral rotation: by the infraspinatus, the teres minor, and the
posterior fibers of the deltoid muscle.
• Medial rotation: by the subscapularis, the latissimus dorsi, the
teres major, and the anterior fibers of the deltoid muscle.
• Circumduction: This is a combination of the above
movements.
Relations:
• Anteriorly: subscapularis muscle, the axillary
vessels and brachial plexus
• Posteriorly: infraspinatus and teres minor
• Superiorly: supraspinatus muscle, subacromial
bursa, coracoacromial ligament, and deltoid
• Inferiorly: long head of the triceps muscle, the
axillary nerve, and the posterior circumflex
humeral vessels
• Nerve supply: by articular twings from
axillary and suprascapular nerves