The arm
The cubital fossa
OBJECTIVES
…
To list the muscles in the flexor & extensor
compartments of the arm
To follow the main vessels & nerves passing
through these compartments
To define the cubital fossa & its contents
Cutaneous innervation:
- Supraclavicular (C4)
- Upper lateral CNA (axillary)
- Lower lateral CNA (radial)
- Posterior CNA (radial)
- Intercostobrachial n (2
nd
& 3
rd
intercostal nerves extending to the arm)
Fascial compartments of the arm:
• The arm is enclosed by a strong layer of deep fascia
• Medial & lateral intermuscular septa extend from this fascial cylinder
towards the humerus being attached to the medial & lateral supracondylar
ridges
• Thus the arm id divided into anterior & posterior compartments
• Each compartment has its own muscles & NV bundles
Muscle
Origin
Insertion
Innervation
Function
Coracobrachialis
Coracoid process
Mid-shaft of
humerus
Musculo-
cutaneous
nerve
•
Shoulder flexor
•
Adductor
Biceps brachii
•
Long head: Supraglenoid
tubercle
•
Short head: Coracoid pr.
Radial tuberosity
•
Elbow flexor
•
Supinator of RUJ
•
Arm flexor
Brachialis
•
Anterior aspect of
humerus
•
Intermuscular septa
Coronoid process &
tuberosity of ulna
Elbow flexor
Muscles:
Biceps brachii:
- The long head as it descends it will pass through the cavity of shoulder joint
- It traverses the bicepital groove
- The heads fuse in the midarm
- Tendon is attached to the posterior part of bicepital tuberosity of radius
(radial tuberosity)
- Bicepital aponeurosis: a ribbon like sheet attached the biceps tendon to the
ulna in the cubital fossa
The brachial artery:
- The continuation of axillary artery at
the lower border of T major
- Ends in the cubital fossa by
dividing into radial & ulnar arteries
- It is the prime artery which supplies
the arm
Relations:
- The artery lies on triceps &
brachialis muscles
- Covered by biceps
- Crossed by medial nerve in the
midarm & bicepital aponeurosis
inferiorly
- Ulnar nerve lies lateral to it
Branches:
1- Muscular;
to arm muscles
2- Nutrient;
to the humerus
3- Profunda brachii;
enters the
triangular
interval
&
accompanies radial nerve in the
back of the arm
4- Superior ulnar collateral a;
arises
in
the
midarm
&
descends with the ulnar n to
the elbow anastomosis
5- Inferior ulnar collateral a;
arises from the end & shares in
elbow anastomosis
The musculocutaneous nerve (C5,6,7):
•
Arises from the lateral cord of brachial plexus
•
Enters the arm by penetrating coracobrachialis
•
Lies between brachialis & biceps to supply arm muscles
•
Leaves the arm lateral to biceps tendon as the LCNF
Other structures which pass in the
anterior brachial compartment:
Median nerve:
•
Lies anterior then medial to the
brachial artery
•
Has no branch in the arm
Ulnar nerve:
•
Along the medial side of the arm
•
In the lower 1/3 pierces the medial
intermuscular septum to lie in the
posterior compartment
•
Has no branch in the arm
Radial nerve:
In the lower 1/3
Muscle
Origin
Insertion
Innervation
Function
Triceps
•
Long head: Infraglenoid
tubercle
•
Medial head: Back of humerus
medial to spiral groove
•
Lateral head: Back of humerus
lateral to the groove
Olecranon
process
•
Radial nerve
•
Axillary n. (LH?)
•
Elbow extensor
•
LH; Shoulder extensor
& adductor
Radial nerve:
- Axilla: gives nerve to medial head of triceps & nerve to anconeus
- Enters the triangular interval with the profundal brachii artery
- In the spiral groove in contact with the bone
- Pierces the lateral septum to enter the anterior compartment in the lower 1/3
Branches:
- Axilla:
Sensory:
posterior CAN
Motor:
nerve to MH & LH of
triceps
- Spiral groove:
Sensory:
Lower lateral CNA,
posterior CNF
Motor:
nerve to MH, lateral H &
anconeus
Radial nerve injury
Wrist drop
Profundal brachii artery:
-
Enters
the
triangular
interval
accompanying
the radial nerve
-
Gives the radial & middle
collateral
branches
to
elbow anastomosis
-
Gives muscular branches
to muscles nearby
-
Ends in the anastomosis
around the elbow
-Triangular depression located anterior to the elbow joint
-Formed between brachioradialis & the pronator teres
-The base of the triangle is an imaginary horizontal line between the medial and
lateral epicondyles
-The floor of the fossa is formed mainly by the brachialis muscle
-The roof is the skin & fascia of the arm strengthened by bicepital aponeurosis
Structures in the roof (medial to lateral):
- Basilic vein
- Medial CNF
- Median cubital vein
- Lateral CNF
- Cephalic vein
Contents (medial to lateral):
- Median nerve
- Brachial artery
- Biceps tendon
- Radial nerve (deep to
brachioradialis!)
Brachial artery bifurcates in
its lower part
Clinical skills:
Venous puncture
(Median cubital vein)
Blood pressure measurement
(Brachial artery)
Anastomosis around the elbow:
• Provides blood to the joint
• Connects the brachial artery proximally
to radial & ulnar arteries distally
Shared arteries:
1- Descending branches:
- Superior ulnar collateral
- Inferior ulnar collateral
- Profunda collaterals (radial & middle)
2- Ascending branches:
- Radial recurrent
- Ulnar recurrent (anterior & posterior)
- Interosseous recurrent