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Anatomy Revision - Upper LimbAxilla
• Think of the axilla and a distorted four sided pyramid. What are its walls? Medial: chest wall and serratus anterior. Anterior:
pectoralis muscles. Lateral: bicipital groove of humerus. Posterior: latissimus dorsi and teres major. What constitute the anterior
(pectoralis muscles) and posterior (latissimus dorsi and teres major) axillary folds?
• List the contents of the axilla. The main things are axillary vessels and branches, cords and branches of brachial plexus, but most
importantly the lymph nodes.
• List the parts and branches of the axillary artery. First part (medial to pectoralis minor): one branch, superior (supreme, highest)
thoracic - quite unimportant. Second part (posterior to pectoralis minor): two branches, lateral thoracic and acromiothoracic
(thoracoacromial) - both moderately important in supplying the breast. Third part (lateral to pectoralis minor): three branches, the
anterior and posterior circumflex humerals which form a ring around the surgical neck of the humerus, and the subscapular which
passes down into the axilla. These three are also moderately important. The most important of these branches is probably the
lateral thoracic which supplies about half the breast tissue.
• Lymph nodes in the axilla are very important. Revise the lymph drainage of the breast. How are lymph nodes disposed in the
axilla? What areas drain to these nodes? There are several groups of nodes: anterior, deltopectoral, subscapular, lateral and so
on, but they all drain to the central group whence the lymph passes to the chest.
• Which nerves traverse the axilla? What is the function of each? The important ones would be the long thoracic (which may be
damaged by trauma or surgery resulting in winging of the scapula (why?), and the main branches of the brachial plexus (median,
ulnar, radial, axillary, musculocutaneous).
• Which nerves supply the anterior (flexor) muscles of the upper limb? Remember that the anterior divisions of the plexus (giving
median, musculocutaneous, ulnar, anterior cutaneous nerves) supply flexors and the anterior aspect of the upper limb, and that
posterior divisions (giving radial, axillary, thoracodorsal, subscapular, posterior cutaneous) supply extensors and the posterior
aspect.
• Describe in detail the lymph drainage of the breast and thoracic walls. Include most of breast to axillary nodes. From medial
portion to parasternal nodes (alongside the internal thoracic artery) and may cross to other side. Also, lower part to nodes of
anterior abdominal wall, possibly even the inguinal. Vessels which pierce the intercostal spaces may allow lymph to pass round in
lymphatics with the main neurovascular bundle backwards to posterior intercostal nodes.
• To which bones is serratus anterior attached? What, therefore, is its function? Give its motor innervation. Serratus anterior is
attached to the upper eight ribs and the medial side of the scapula. If you are a quadruped, it is one of the muscles that suspends
the trunk from the limb girdle. If you are plantigrade, it is used in protraction of the upper limb - punching. Its motor supply is from
the long thoracic nerve (C567) from the roots of the brachial plexus.
• Which structures may be damaged by penetrating injuries immediately above the clavicle? Apex of the lung, subclavian vessels,
upper trunk and roots of brachial plexus.
• Describe the sternoclavicular joint. When does it move? It is a synovial joint which overlies the junction of the subclavian vein and
the internal jugular vein to form the brachiocephalic vein. It moves every time you move your upper limb. It is, therefore, very
disabling if this joint is diseased.
, Shoulder
• Why are these posterior muscles (except trapezius) supplied by anterior primary rami? Because they are limb muscles - they
attach the limb to the trunk - and only anterior rami supply limbs (don’t be confused by the fact that the anterior rami divide into
anterior and posterior divisions).
• When does the scapula move? how? at which joints? Explain the role of the scapula in abduction of the shoulder joint. The
scapula glides over the surface of the chest as the arm moves. In particular, the scapula moves when the arm is abducted more
than 90°. It is moved by serratus anterior and trapezius.
• Follow the axillary nerve from the posterior cord of the brachial plexus. At what site is it in danger of damage and how do you test
it? Surgical neck of the humerus (so may be damaged in fractures here or dislocations of the shoulder). Test by skin sensation over
the insertion of deltoid. Axillary nerve also supplies deltoid which is the main abductor. Depending on the nature of the injury, this
may be a possible test. Serratus anterior would be affected. Protraction of the scapula (as in punching etc) would be weakened.
Scapular rotation would be affected so abduction of the shoulder beyond 90° would be weakened.
• What is the triangular space? Quadrangular space? What passes through them? The triangular space is between long head of
triceps, teres major and humerus and contains the radial nerve and profunda brachii artery as they enter the spiral groove. The
axillary nerve passes through the quadrangular space just medial to the upper end of the humerus. The radial nerve passes
through a triangular space just distal to the quadrangular space. The long head of triceps forms the medial boundary of both
spaces.
• Capsule of the shoulder joint - what are its attachments to the surrounding bones? The capsule is loose (to allow for much
movement). It is attached to the margins of the glenoid cavity above, in front and behind. This allows a certain laxity which can
be taken up in extreme shoulder abduction. On the humerus the capsule is attached to the anatomical neck with its fibres
arching in front between the margins of the bicipital groove (greater and lesser tuberosities). This allows the tendon of the long
head of the biceps to emerge.
• How are joints supplied with arterial blood? Profuse arterial anastomoses with branches from all neighbouring main arteries.
• How are bones supplied with arterial blood? (1) a nutrient artery which generally enters mid shaft and passes into the marrow
cavity for haemopoiesis and gives branches into the Haversian canals; (2) numerous small branches which penetrate the
periosteum directly, especially at places where muscles are attached; and (3) branches which enter at the attachment of joint
capsules - the capsular or retinacular vessels.
• What movements take place at the shoulder joint? Which muscles produce them? How are these muscles innervated? There are
so many - it is a very mobile joint. Flexion: pectorals (pectoral nerves). Extension; posterior scapular muscles (branches of the
posterior cord). Adduction: gravity and pectorals. Abduction: Deltoid, supraspinatus, trapezius, serratus anterior.
• What is the function of the following muscles: triceps brachii (elbow extension), biceps brachii (forearm supinator, elbow and
shoulder flexor), brachialis (elbow flexor)?
• How may blood in the first part of the subclavian artery may reach the axillary artery following occlusion of the 2nd and 3rd parts
of the subclavian artery? Scapular anastomosis - look it up.
• What would result from pressure (a) in the arm on the radial nerve - weakness of forearm extensors and sensory loss on the
extensor aspect; and (b) in the axilla on the long thoracic nerve (winging of the scapula because of weakness of serratus
anterior)?
• Describe the lymphatic drainage of the upper limb. The important thing is that lymph from the medial (little finger) side passes to
(medial) epitrochlear nodes at the elbow before arriving at the axillary nodes. From the lateral (thumb) side there are no nodes
until those in the deltopectoral triangle are reached.
• Describe the venous drainage of the upper limb. Deep and superficial. A plexus of deep veins run with the main arteries (venae
comitantes) and unite to form the axillary vein. Superficial veins are visible under the skin and pass up to penetrate the deep
fascia at some point before joining the axillary or subclavians veins.
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