TBL5 - Axilla

Question 1

How are deep fascia named?

Answer 1

Deep fascia, a tough sheet of dense connective tissue, is named by the tissue it covers

Question 2

Where are the pectoral and axillary fascia? What is the function of the axillary fascia?

Answer 2

1) The pectoral fascia surrounds the pectoralis major, forming
the anterior layer of the anterior axillary wall
2) Axillary fascia forms the floor of the axilla and is continuous with the pectoral fascia
3) The pectoral fascia leaves the lateral border of the pectoralis major to become the axillary fascia, which surrounds the neurovascular contents of the axilla

Question 3

Describe the location and function of the axilla

Answer 3

1) 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
2) The subscapularis, serratus anterior, and pectoralis major muscles form the posterior, medial, and anterior boundaries of the axilla, respectively
3) The axilla is a passageway, or “distribution center,” usually protected by the adducted upper limb, for nerves and blood vessels from the root of the neck to the upper extremities

Question 4

Where are the subclavian, axillary, & subscapular arteries located?

Answer 4

1) The subclavian artery, which receives blood from the aorta, is continuous with the axillary artery at the lateral border of the first rib
2) The axillary artery ends at the inferior border of the teres major where it continues as the brachial artery
3) The subscapular artery is the branch of the axillary artery with the largest diameter and shortest length

Question 5

Where is the circumflex scapular artery located? What does it anastomose with?

Answer 5

The circumflex scapular artery, a terminal branch of the subscapular artery, curves around the lateral border of the scapula to enter the infraspinous fossa, anastomoses with the suprascapular artery, a branch of subclavian artery, on the posterior side of the scapula

Question 6

What are the two branches of the subscapular artery? What muscle does the thoracodorsal artery supply?

Answer 6

1) Circumflex scapular & Thoracodorsal arteries

2) The thoracodorsal artery travels inferiorly with the thoracodorsal nerve and supplies the latissimus dorsi

Question 7

What arteries supply the deltoid? Where do they travel from?

Answer 7

1) The posterior circumflex humeral artery arises from the axillary artery and encircles the humerus to anastomose with the anterior circumflex humeral artery, a smaller branch of the axillary artery
2) The circumflex arteries supply the deltoid

Question 8

Where can the axillary artery be ligated without stopping blood flow into the upper limb?

Answer 8

1) The importance of the collateral circulation made possible by these anastomoses becomes apparent when ligation of a lacerated subclavian or axillary artery is necessary
2) For example, the axillary artery may have to be ligated between the 1st rib and subscapular artery
3) The direction of blood flow in the subscapular artery is then reversed, enabling blood to reach the third part of the axillary artery

Question 9

Where does the axillary vein become the subclavian vein? What other veins join the subclavian vein along with the axillary vein?

Answer 9

1) The axillary vein, which becomes the subclavian vein at the lateral border of the first rib
2) The axillary vein receives tributaries corresponding to branches of the axillary artery

Question 10

How many groups of axillary lymph nodes are there? Where do they drain?

Answer 10

1) 5 groups of axillary lymph nodes drain mainly into the supraclavicular nodes
2) Lymph vessels from the supraclavicular lymph nodes drain into veins in the root of the neck

Question 11

How is lymph fluid obtained in the axillary lymph nodes?

Answer 11

Lymphatic vessels accompany veins of the upper limb and transport lymph into the axillary lymph nodes

Question 12

Compare regional lymph drainage into the subscapular & humeral nodes

Answer 12

1) The subscapular (posterior) nodes consist of six or seven nodes that lie along the posterior axillary fold and subscapular blood vessels. These nodes receive lymph from the posterior aspect of the thoracic wall and scapular region
2) The humeral (lateral) nodes consist of four to six nodes that lie along the lateral wall of the axilla, medial and posterior to the axillary vein. These nodes receive nearly all the lymph from the upper limb, except that carried by the lymphatic vessels accompanying the cephalic vein, which primarily drain directly to the apical axillary and infra clavicular nodes

Question 13

Where do the axillary pectoral, subscapular, & humeral nodes drain their lymph fluid to?

Answer 13

1) Lymph vessels from the three groups of nodes transport lymph to the central and apical nodes for further filtration
2) Lymph from the apical nodes drains into the supraclavicular nodes

Question 14

Which two nerves are at risk during surgical removal of pathologic axillary nodes? Why can removal result in lymphedema?

Answer 14

1) During axillary node dissection, two nerves are at risk of injury
a) During surgery, the long thoracic nerve to the serratus anterior is identified and maintained against the thoracic wall. Cutting the long thoracic nerve results in a winged scapula
b) If the thoracodorsal nerve to the latissimus dorsi is cut, medial rotation and adduction of the arm are weakened, but deformity does not result
2) Lymphatic drainage of the upper limb may be impeded after the removal of the axillary nodes, resulting in lymphedema, swelling as a result of accumulated lymph, especially in the subcutaneous tissue

Question 15

What is the brachial plexus? Where is it located?

Answer 15

1) Most nerves in the upper limb arise from the brachial plexus, a major nerve network supplying the upper limb; it begins in the neck and extends into the axilla. Almost all branches of the plexus arise in the axilla (after the plexus has crossed the 1st rib)
2) The brachial plexus is formed by the union of the anterior rami of the last four cervical (C5–C8) and the first thoracic (T1) nerves, which constitute the roots of the brachial plexus

Question 16

What are three trunks formed by the brachial plexus? What are two divisions formed by the trunk underneath the clavicle?

Answer 16

1) A superior trunk, from the union of the C5 and C6 roots
2) A middle trunk, which is a continuation of the C7 root
3) An inferior trunk, from the union of the C8 and T1 roots
4) Each trunk of the brachial plexus divides into anterior and posterior divisions as the plexus passes through the cervico-axillary canal posterior to the clavicle

Question 17

How do the anterior and posterior divisions of the trunks join to form the lateral, medial, & posterior cords?

Answer 17

The divisions of the trunks form three cords of the brachial plexus:

1) Anterior divisions of the superior and middle trunks unite to form the lateral cord 2) Anterior division of the inferior trunk continues as the medial cord
3) Posterior divisions of all three trunks unite to form the posterior cord

Question 18

Where do the cords lie and how are they named?

Answer 18

The cords bear the relationship to the second part of the axillary artery that is indicated by their names. For example, the lateral cord is lateral to the axillary artery

Question 19

What are the roots that generate the dorsal scapular nerve & long thoracic nerve? What generates the suprascapular nerve?

Answer 19

1) Dorsal scapular nerve is generated by the posterior aspect of anterior ramus of C5 with a frequent contribution from C4
2) Long thoracic nerve is generated by posterior aspect of anterior rami of C5, C6, C7
3) Suprascapular nerve is generated by the superior trunk, receiving fibers from C5, C6 and often C4

Question 20

What muscles are innervated by the dorsal scapular nerve, the long thoracic nerve, & the suprascapular nerve respectively?

Answer 20

1) The dorsal scapular nerve innervates Rhomboids; occasionally supplies levator scapulae
2) The long thoracic nerve innervates the serratus anterior
3) The suprascapular nerve innervates the supraspinatus and infraspinatus muscles

Question 21

How does avulsion of brachial plexus roots C5 and C6 typically occur in adults and newborns?

Answer 21

1) Injuries to superior parts of the brachial plexus (C5 and C6) usually result from an excessive increase in the angle between the neck and shoulder. These injuries can occur in a person who is thrown from a motorcycle or a horse, and lands on the shoulder in a way that widely separates the neck and shoulder. When thrown, the person’s shoulder often hits something and stops, but the head and trunk continue to move. This stretches or ruptures superior parts of the brachial plexus or avulses (tears) the roots of the plexus from the spinal cord.
2) Injury to the superior trunk of the plexus is apparent by the characteristic position of the limb (“waiter’s tip position”), in which the limb hangs by the side in medial rotation. Upper brachial plexus injuries can also occur in a neonate when excessive stretching of the neck occurs during delivery
3) As a result of injuries to the superior parts of the brachial plexus (Erb-Duchenne palsy), paralysis of the muscles of the shoulder and arm supplied by the C5 and C6 spinal nerves occurs: deltoid, biceps, and brachialis. The usual clinical appearance is an upper limb with an adducted shoulder, medially rotated arm, and extended elbow. The lateral aspect of the forearm also experiences some loss of sensation
4) Chronic microtrauma to the superior trunk of the brachial plexus from carrying a heavy backpack can produce motor and sensory deficits in the distribution of the musculocutaneous and radial nerves. A superior brachial plexus injury may produce muscle spasms and severe disability in hikers (backpacker’s palsy) who carry heavy backpacks for long periods