Upper Limb

Arm
 Objectives

•Define the arm compartments with their contents.

•Describe the anatomy of the muscles of the front

and back of the arm.
• Identify the neurovascular bundle traversing the arm
 Compartments of The Arm
- Two compartments; anterior and posterior, by two Anterior

intermuscular septa ( medial and lateral ).

A) The anterior compartment of the arm:

Three muscles; coracobrachialis, biceps and brachialis (flexor of the

elbow joint) and are supplied by musculocutaneous nerve.

B) The posterior compartment:

- Contains the triceps muscle (extensor of the elbow joint); and is

supplied by the radial nerve.

- Nerves: of arm includes; Musculocutaneous nerve , radial nerve

, part of course of median and ulnar nerves.

- The artery: is the brachial artery and its branches. Posterior

 Muscles of the arm
Coracobrachialis:
Origin: From tip of the coracoid process of the

scapula together with the short head of biceps .

Insertion: It is inserted into the middle of the

medial border of the humerus.

Nerve Supply: It is innervated by the

musculocutaneous nerve.

Action: It helps in the flexion & adduction of

shoulder joint .
Musculocutaneous nerve
Biceps brachii:
Origin :
1-Short head: from tip of the coracoid process together with the
coracobrachialis.
2-Long head: by a tendon from the supraglenoid tubercle.

Insertion:
- By a single tendon into “radial tuberosity” ; from the medial
border of this tendon, the “bicipital aponeurosis” passes
medially and downwards to be attached into the deep fascia of
the forearm.

- The aponeurosis protects the underlying brachial artery and

median nerve.

Nerve supply: Musculocutaneous nerve.

Action:
The muscle crosses three joints ; shoulder, elbow and
superior radioulnar, so it can, therefore act on all of
them.
1. The short head is a flexor of the shoulder joint; the
long head helps to keep the head of the humerus in
normal position during movements at this joint.
2. It is a powerful flexor of the forearm at the elbow
joint.
3. It is also the most powerful supinator of the
forearm when the elbow joint is flexed as tightening
the screw with screw driver.
Brachialis:
Origin: The muscle arises from the lower half
of the anterior surface of the humerus.

Insertion: It is inserted into the ulnar

tuberosity and coronoid process.

Nerve supply: Mainly by the

musculocutaneous nerve; the radial nerve
supplies the lateral part of the muscle (double
nerve supply).

Action: It is the principal flexor (pure flexion)

of the elbow joint.
Triceps brachii:
Origin (3 heads):
1-Long head: arises from the infraglenoid tubercle of the scapula.

2-Medial head: arises from the lower half of the posterior surface of

the shaft of the humerus below the spiral (radial) groove.

3-Lateral head: arises from oblique line above the radial groove

(spiral) of the humerus.

Insertion: The three heads form a large tendon which inserts into
the upper surface of the olecranon process of the ulna.

Nerve supply: By the radial nerve .

Action: Extension of the forearm at the elbow joint.

Nerves of the arm:
Musculocutaneous: nerve of the anterior
compartment of the arm.
Radial: for the posterior compartment of
the arm.
Ulnar: crossing the arm giving no
branches.
Median: crossing the arm giving no
branches.
 Nerves of the arm
Musculocutaneous nerve :
Origin: From the lateral cord of the brachial plexus (C5, 6, 7).

Course and relations:

- The nerve enters the arm by passing through the coracobrachialis muscle; it

then descends between the biceps brachii and the brachialis muscles;

supplying them, emerging lateral to the tendon of the biceps brachii muscle at

the elbow, continues as the lateralcutaneous nerve of the forearm.

Branches:

1. Muscular: to coracobrachialis , biceps brachii and brachialis.

2. Lateral cutaneous nerve of forearm: to the skin of lateral surface of forearm .

3. Articular: to elbow and shoulder joints.

Median nerve:
Origin: The median nerve arises by two roots:
1. Lateral root (C.5, 6, 7): from the lateral cord of the brachial
plexus.
2. Medial root (C. 8, T.1): from the medial cord of the brachial
plexus; the two roots unite forming the median nerve on the
lateral side of 3rd part of axillary artery.

Course of median nerve in the arm:

- It passes vertically down in the arm lateral to the brachial artery
(upper part); about the middle of the arm, it crosses in front of
the brachial artery, then descends on its medial side to enter the
cubital fossa medial to brachial artery

Branches: The median nerve has no major branches in the arm

Ulnar nerve:
Origin: It is a branch of the medial cord of the brachial plexus (C.7, 8,

and T.1).

Course of ulnar nerve in the arm :

- It descends on the medial side of the third part of the axillary

artery and brachial artery .

- At the middle of the arm , it pierces the medial intermuscular

septum to enter the posterior compartment of the arm; then it

descends accompanied with superior ulnar collateral artery,

passing behind the medial epicondyle of the humerus (dangerous

position).

- The ulnar nerve has no branches in the arm

Radial nerve:
Origin: It arises from the posterior cord of the brachial plexus (C.5, 6,7, 8
and T.1), It is the largest branch of the brachial plexus .
Course of radial nerve in the arm :
- It descends behind the third part of the axillary artery and then behind
the brachial artery , accompanied by the profunda brachii artery .
- Then it enters the posterior compartment of the arm; then, the nerve
passes obliquely between the lateral and medial heads of the triceps
brachii muscle to reach the spiral groove.
- At the middle of the arm, the radial nerve pierces the lateral
intermuscular septum to enter the anterior compartment of the arm
and then descends in a groove between the brachialis and the
brachioradialis muscles.
1. In the axilla:
a. Nerves to long and medial heads of triceps.
b. Posterior cutaneous nerve of the arm.

2. In the spiral groove:

a. Nerves to lateral and medial heads of triceps.
b. Nerve to anconeus.
c. Lower lateral cutaneous nerve of the arm.
d. Posterior cutaneous nerve of forearm.

3. In the anterior compartment of the arm:

a. Nerves to brachialis, brachioradialis, and extensor carpi radialis
longus.
b. Articular branches to the elbow joint.
c. Deep radial nerve. Terminal branches
d. Superficial radial nerve.
 Blood vessels of arm
Brachial artery:
- Beginning: as a continuation of the axillary artery at the lower border of

the teres major.

- Termination: in the cubital fossa at the level of the neck of the radius by

dividing into radial and ulnar arteries.

Course:

- In the upper part of the arm, the brachial artery is medial to the humerus,

then becomes in front of the humerus in the lower part of the arm and

separated from it by the brachialis muscle.

- The brachial artery is palpable along its whole course since it is only

covered by skin and fascia.

Important relations:
- The artery is covered by skin and fascia
throughout its course (easy to palpate).
- It is crossed by median nerve at
middle of the arm (from lateral to
medial)??.
- Radial nerve is posterior to upper part
and brachialis to its lower part.
- Ulnar nerve is medial to its upper
part,
Branches:

1.Profunda brachii artery (deep brachial artery):

- Largest branch of the brachial artery, arising close to the
lower border of the teres major muscle.
- It enters the posterior compartment of the arm with the
radial nerve and together they pass downwards, laterally
between the long and medial heads of the triceps to reach
the spiral groove.

- In the spiral groove, it divides into ascending and

descending branches.
- It gives muscular branches to the muscles of the
posterior compartment and nutrient branch to the
humerus.
2. Nutrient artery: to the humerus.

3. Muscular branches: to the muscles of the anterior

compartment of the arm.

4. Superior ulnar collateral artery: passes downwards and

medially accompanying the ulnar nerve and both of them
pierce the medial intermuscular septum to descend behind
the medial epicondyle.

5. Inferior ulnar collateral artery: divides into anterior and

posterior branches which descend in front of and behind
the medial epicondyle of the humerus.

6. Terminal branches: which are the radial and ulnar

arteries