Axilla Practical

Anatomy Practical: Axilla
Activity 1: Axilla and Other Spaces
i) The axilla is the pyramidal space inferior to the glenohumeral joint and superior to the axillary fascia at the junction of the arm and thorax.
 The anterior axillary fold is the inferiormost part of the anterior wall that may be grasped between the fingers; it is formed by the pectoralis major, as it bridges from thoracic wall to humerus, and the overlying integument.
 The posterior axillary fold is the inferiormost part of the posterior wall that may be grasped. It extends farther inferiorly than the anterior wall and is formed by latissimus dorsi, teres major, and overlying integument.
ii)
• -superiorly:
o and ventrally: subscapularis
o and dorsally: teres minor
• inferiorly: teres major
• medially: long head of triceps
• laterally: humerus
-It transmits the axillary nerve, posterior circumflex humeral vein, posterior circumflex humeral artery.
iii) It has the following boundaries:
• the Teres major inferiorly
• the long head of the Triceps laterally
• For the superior border, some sources list the Teres minor, while others list the Subscapularis.
-Contents: the scapular circumflex artery and vein.
-It arises from the subscapular artery.
-It arises together with the thoracodorsal artery.
The latissimus dorsi.
Activity 2: Blood Supply
i) The axillary artery begins at the lateral border of the 1st rib as the continuation of the subclavian artery and ends at the inferior border of the teres major. It passes posterior to the pectoralis minor into the arm and becomes the brachial artery when it passes the inferior border of the teres major, at which point it usually has reached the humerus.
 The first part of the axillary artery is located between the lateral border of the 1st rib and the medial border of the pectoralis minor; it is enclosed in the axillary sheath.
The second part of the axillary artery lies posterior to pectoralis minor and has two branches.
The third part of the axillary artery extends from the lateral border of pectoralis minor to the inferior border of teres major.
 First part has 1 branch-superior thoracic artery
Second part( 2 brahcnes)-thoracoacromial and lateral thoracic arteries.
Third part( 3 branches)-subscapular artery( largest branch), anterior circumflex humeral and posterior circumflex humeral arteries.
 Subscapular artery receives blood through several anastomoses with the suprascapular artery, dorsal scapular artery, and intercostal arteries. Clinical importance: when ligation of a lacerated subclavian or axillary artery is necessary. For example, the axillary artery may have to be ligated between the 1st rib and subscapular artery; in other cases, vascular stenosis of the axillary artery may result from an atherosclerotic lesion that causes reduced blood flow.
 All the branches of the axillary artery except the circumflex humeral arteries.

ii) Suprascapular artery.
Passes inferolaterally crossing anterior scalene muscle, phrenic nerve, subclavian artery, and brachial plexus running laterally posterior and parallel to clavicle; next it passes over transverse scapular ligament to supraspinous fossa; then lateral to scapular spine (deep to acromion) to infraspinous fossa on posterior surface of scapula.
 Origin: Thyrocervical (or as direct branch of subclavian artery) 2 other arteries:Suprasternal branch, which crosses over the sternal end of the clavicle to the skin of the upper part of the chest; and an acromial branch, which pierces the trapezius and supplies the skin over the acromion.
 Origin: Superior trunk, receiving fibres from C5, C6 and often C4. Passes laterally across lateral cervical region (posterior triangle of neck), superior to brachial plexus; then through scapular notch inferior to superior transverse scapular ligament.
 A thin flat ligament that is attached at one end to the coracoid process, bridges over the suprascapular notch converting it into a foramen, and is attached at the other end to the upper margin of the scapula on its dorsal surface—called also superior transverse scapular ligament.
 Clinical relevance: The suprascapular nerve arises from the lateral aspect of the upper trunk of the brachial plexus, runs across the posterior triangle of the neck together with the suprascapular artery and the omohyoid muscle, dips under the trapezius, and then passes through the suprascapular notch at the superior border of the scapula. As the nerve enters the supraspinous fossa, it supplies the supraspinatus muscle, then curls tightly around the base of the spine of the scapula, enters the infraspinous fossa, and supplies the infraspinatus.6 A stout, strong suprascapular ligament closes over the free upper margins of the suprascapular notch. Suprascapular nerve entrapment is caused by this ligament, often in conjunction with a tight, bony notch. The only sensory fibers in the suprascapular nerve supply the posterior aspect of the shoulder joint. These articular fibers are the source of the ill-localized, dull shoulder pain of the syndrome. The syndrome often afflicts athletes, particularly those involved in basketball, volleyball, weightlifting, and gymnastics.

 Paralysis and anesthesia. Causes are disease, stretching and wounds in the lateral cervical region ( cervical triangle) of the neck or in axilla.
 Paralysis divided into 2-complete and incomplete. In complete paralysis, no movement is detectable. In incomplete paralysis- movements are weak compared with those on normal side. Anesthesia- unable to feel pain( test by pinprick of skin)
 General appearance: usual clinical appearance is an upper limb with an adducted shoulder, medially rotated arm, and extended elbow.Position attained by paralysis of the muscles of the shoulder and arm supplied by the C5 and C6 spinal nerves occurs: deltoid, biceps, and brachialis.
Axillary nerve. Origin-Terminal branch of posterior cord, receiving fibers from C5, C6. Course : Exits axillary fossa posteriorly, passing through quadrangular space with posterior circumflex humeral artery ; gives rise to superior lateral brachial cutaneous nerve; then winds around surgical neck of humerus deep to deltoid.
 Originates from posterior chord.
 Muscles it supply : teres minor,deltoid.
 Since teres minor and deltoid moves the glenohumeral joint, the axillary nerve also supplies the axillary nerve according to Hilton’s law. The axillary nerve also supplies the skin of superolateral arm( over inferior part of deltoid) according to Hilton’s law.
 Axillary nerve dysfunction is a form of peripheral neuropathy. It occurs when there is damage to the axillary nerve, which supplies the deltoid muscles of the shoulder. A problem with just one nerve group, such as the axillary nerve, is called mononeuropathy.
The usual causes include direct trauma, prolonged pressure on the nerve, and compression of the nerve from nearby body structures. Entrapment involves pressure on the nerve where it passes through a narrow structure.
The damage may include destruction of the myelin sheath of the nerve or destruction of part of the nerve cell (the axon). Damage to the axon slows or prevents conduction of impulses through the nerve.
Direct injury to the shoulder and pressure on the nerve can lead to axillary nerve dysfunction.
 Numbness of part of outer shoulder, shoulder weakness, difficulty lifting objects with arm, difficulty lifting objects above the head. Physicians can use electromyography (EMG) to assess the health of muscles and nerves that control the muscle. The health care provider will insert a very thin needle electrode through the skin into the muscle. The electrode on the needle picks up the electrical activity given off by your muscles. This activity is displayed on a special monitor called an an oscilloscope, and may be heard through a speaker.After placement of the electrodes, you may be asked to contract the muscle. For example, bending your arm. The presence, size, and shape of the wave form -- the action potential -- produced on the monitor provide information about your muscle's ability to respond when the nerves are stimulated. Nerve biopsy can also be performed.
c. Cephalic vein located in the superficial fascia along the anterolateral surface of the biceps brachii muscle.
 Superiorly the cephalic vein passes between the deltoid and pectoralis major muscles (deltopectoral groove) and through the deltopectoral triangle, where it empties into the axillary vein.
 Its location in the deltopectoral groove is fairly consistent, making this site a good candidate for cannulation. It is often referred to as the 'House-man's Friend' for this reason and is generally a good place for cannulaton when a large bore cannula needs to be sited. A cannula is a tube that can be inserted into the body often for the delivery or removal of fluid.