2. COMPARTMENTS OF THE ARM
The arm is divided into anterior and posterior compartments
by extension of deep fascia which are called the medial
and lateral intermuscular septa.
– These septa provide additional surface for the attachment of
muscles.
– They also form planes along which nerves and blood vessels
travel.
– The septa are well defined only in the lower half of the arm and
are attached to the medial and lateral borders and supracondylar
ridges of the humerus.
The medial septum is pierced by the ulnar nerve and the
superior ulnar collateral artery; the lateral septum is
pierced by the radial nerve and the anterior descending
branch of the profunda brachii artery.
3. COMPARTMENTS OF THE ARM
• Two additional septa are present in the anterior
compartment of the arm.
• The transverse septum separates the biceps from
the brachialis and encloses the musculocutaneous
nerve.
• The anteroposterior septum separates the
brachialis from the muscles attached to the lateral
supracondylar ridge; it encloses the radial nerves
and the anterior descending branch of the
profunda brachii artery.
4. THE ANTERIOR COMPARTMENT
• There are three muscles located in the anterior
compartment of the upper arm.
• A good memory aid for this is BBC –
– Biceps ,
– Brachialis ,
– Coracobrachialis .
• Arterial supply to the anterior compartment of the
upper arm is via muscular branches of the Brachial
artery.
• They are all innervated by the Musculocutaneous
nerve.
5. THE POSTERIOR COMPARTMENT
• The posterior compartment of the upper arm
contains the triceps brachii muscle, which has
three heads. The medial head lies deeper than
the other two, which cover it.
• Arterial supply to the posterior compartment
of the upper arm is via the profunda brachii
artery.
6. Biceps Brachii
• The biceps brachii is a two-headed muscle. Although
the majority of the muscle mass is located anteriorly to
the humerus, it has no attachment to the bone itself.
• As the tendon of biceps brachii enters the forearm, a
connective tissue sheet is given off – the bicipital
aponeurosis. This forms the roof of the cubital
fossa and blends with the deep fascia of the anterior
forearm.
• Attachments: Long head originates from the
supraglenoid tubercle of the scapula, and the short
head originates from the coracoid process of the
scapula. Both heads insert distally into the radial
tuberosity and the fascia of the forearm via the bicipital
aponeurosis.
7.
8. Biceps Brachii
• Function: Supination of the forearm.
It also flexes the arm at the elbow
and at the shoulder.
–The long head keeps the head of
humerus in place.
• Innervation: Musculocutaneous
nerve. The bicep tendon reflex tests
spinal cord segment C6.
9. Clinical Relevance
• Biceps reflex: It is tested during physical
examination by tapping the tendon of biceps
brachii by reflex hammer with forearm
pronated and partially extended at elbow. The
normal reflex is brief jerk-like flexion of the
elbow. The normal reflex confirms the
integrity of musculocutaneous nerve and C5
and C6 spinal segments.
10. Coracobrachialis
• The coracobrachialis muscle lies deep to the biceps
brachii in the arm.
• Attachments: Originates from the coracoid process
of the scapula. The muscle passes through
the axilla, and attaches the medial side of the
humeral shaft, at the level of the deltoid tubercle.
• Function: Flexion of the arm at the shoulder, and
weak adduction.
• Innervation: Musculocutaneous nerve.
11.
12. Brachialis
• The brachialis muscle lies deep to the biceps
brachii, and is found more distally than the other
muscles of the arm. It forms the floor of the
cubital fossa.
• Attachments: Originates from the medial and
lateral surfaces of the humeral shaft and inserts
into the ulna tuberosity, just distal to the elbow
joint.
• Function: Flexion at the elbow.
• Innervation: Musculocutaneous nerve, with
contributions from the radial nerve.
13.
14. Anatomical Events at the Insertion Of
Coracobrachialis
1. Circular shaft of the humerus becomes triangular below this
level.
2. Brachial artery passes from medial side of arm to its anterior
aspect.
3. Basilic vein pierces the deep fascia.
4. Median nerve crosses in front of the brachial artery from
the lateral to medial side.
5. Radial nerve pierces lateral intermuscular septum to pass
from the posterior compartment to the anterior
compartment.
6. Ulnar nerve pierces medial intermuscular septum to go into
the posterior compartment.
7. Medial cutaneous nerve of the arm and forearm pierces the
deep fascia.
8. Nutrient artery pierces the humerus.
15. Morphology of the coracobrachialis
• It represents the muscle of medial compartment of the
forelimb of quadrupeds, which is not well-developed in
human beings.
• In some animals, this muscle consists of three heads. In
human beings, the upper two heads are fused and
musculocutaneous nerve passes between the two
fused heads. The lower third head has disappeared in
humans.
• Occasionally the lower head persists as a fibrous
band (ligament of Struthers), which extends between
supratrochlear/trochlear spur and medial epicondyle of
the humerus. The median nerve and brachial artery
then pass deep to the ligament and may be
compressed.
16.
17. Triceps Brachii
• Attachments: Long head – originates
from the infraglenoid tubercle.
–Lateral head – originates from the humerus,
superior to the radial groove.
–Medial head – originates from the humerus,
inferior to the radial groove.
• Distally, the heads converge onto one
tendon and insert into the olecranon of
the ulna.
18. Triceps Brachii
• Function: Extension of the arm at the
elbow.
• Innervation: Radial nerve. A tap on the
triceps tendon tests spinal segment C7.
–Note: In some individuals, the long head of
the triceps brachii is innervated by the
axillary nerve.
19.
20.
21. Clinical Significance
• Injury of radial nerve in radial groove:
• If the radial nerve is damaged in the
radial groove, the extension of elbow
and triceps reflex is not lost because
nerve to long head arises from the
radial nerve in axilla.
22. ANCONEUS
• Anconeus connects the medial
aspect of the ulna to the lateral
aspect of the humerus and is a short
triangular elbow muscle.
• It is occasionally classified as a
branch of the triceps brachii muscle,
due to its location and functionality.
23.
24. ANCONEUS
• ORIGIN
– It arises from the lateral epicondyle of the humerus and
has a wide attachment within the posterolateral surface
of the olecranon as well as associated posterior surface
of the ulna, by its own different tendon.
• Insertion
– Inserts at the olecranon of the ulna.
• Functions
– Mainly to allow a person to extend his elbow and
rotate the forearm. This action is used to carry
something, as a food server would.
