S6) Pectoral Region, Axilla and Brachial Plexus Flashcards

1
Q

What is the pectoral region?

A

The pectoral region is a region located on the anterior chest wall and contains four muscles that exert a force on the upper limb

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2
Q

Identify the 4 muscles in the pectoral region

A
  • Pectoralis major
  • Pectoralis minor
  • Serratus anterior
  • Subclavius
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3
Q

State the structure and function of pectoralis major

A
  • Structure: most superficial muscle in the pectoral region, composed of a sternal head and a clavicular head

- Function: adduction, medial rotation, flexion (clavicular head)

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4
Q

State the origin and attachments of pectoralis major

A
  • Origins:

I. Clavicular head – anterior surface of medial clavicle

II. Sternocostal head – anterior surface of sternum, superior six costal cartilages and aponeurosis of external oblique muscle

  • Attachments: intertubercular sulcus of the humerus
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5
Q

Which nerve(s) innervate pectoralis major?

A
  • Lateral pectoral nerve
  • Medial pectoral nerve
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6
Q

State the structure and function of pectoralis minor

A
  • Structure: lies deep to pectoralis major, forms part of the anterior wall of the axilla region

- Function: stabilises the scapula by drawing it anteroinferiorly against the thoracic wall

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7
Q

State the origins and attachments of pectoralis minor

A
  • Origins: 3rd-5th ribs
  • Attachments: coracoid process of the scapula
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8
Q

Which nerve(s) innervates pectoralis minor?

A

Medial pectoral nerve

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9
Q

State the structure and function of serratus anterior

A
  • Structure: located laterally in the chest wall, forming the medial border of the axilla region

- Function: rotates the scapula, allowing the arm to be raised over 90o

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10
Q

State the origins and attachments of the serratus anterior

A
  • Origins: lateral aspects of ribs 1-8
  • Attachments: costal surface of the medial border of the scapula
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11
Q

Which nerve(s) innervate serratus anterior?

A

Long thoracic nerve

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12
Q

State the structure and function of the subclavius

A
  • Structure: small muscle, located directly deep to the clavicle

- Function: anchors and depresses the clavicle

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13
Q

State the origins and attachments of subclavius

A
  • Origins: junction of the 1st rib and its costal cartilage
  • Attachments: inferior surface of the middle 1/3 of the clavicle
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14
Q

Which nerve(s) innervate subclavius?

A

Nerve to subclavius

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15
Q

What is the axilla region?

A

The axilla region is an area that lies underneath the shoulder joint, at the junction of the upper limb and the thorax, acting as a passageway for neurovascular and muscular structures

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16
Q

What are the 6 borders of the axilla region?

A
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17
Q

Which structures form the apex and base of the axilla region?

A
  • Apex – lateral border of the first rib, superior border of scapula, and the posterior border of the clavicle
  • Base – axillary fascia and skin
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18
Q

Which structures form the lateral and medial walls of the axilla region?

A
  • Lateral wall – intertubercular groove of the humerus
  • Medial wall – serratus anterior and thoracic wall (ribs and intercostal muscles)
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19
Q

Which structures form the anterior and posterior walls of the axilla region?

A
  • Anterior wall – pectoralis major, pectoralis minor, subclavius muscles
  • Posterior wall – subscapularis, teres major and latissimus dorsi
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20
Q

Identify the three main routes by which structures leave the axilla

A
  • Inferiorly and laterally, into the upper limb (main route)
  • Through the quadrangular space
  • Through the clavipectoral triangle
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21
Q

What is the quadrangular space?

A

The quadrangular space is a gap in the posterior wall of the axilla, allowing access to the posterior arm and shoulder area

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22
Q

Identify 2 structures which pass through the quadrangular space

A
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23
Q

What is the clavipectoral triangle?

A

The clavipectoral triangle is an opening in the anterior wall of the axilla which is bound by the pectoralis major, deltoid, and clavicle

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24
Q

Identify 3 structures which pass through the clavipectoral triangle

A
  • Cephalic vein (enter)
  • Medial pectoral nerve (exit)
  • Lateral pectoral nerve (exit)
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25
Q

Identify the 5 clinically important contents of the axilla region

A
  • Axillary artery
  • Axillary vein
  • Brachial plexus
  • Biceps brachii and coracobrachialis
  • Axillary lymph nodes
26
Q

What is the axillary artery?

A

The axillary artery is the main artery supplying the upper limb

27
Q

What is the axillary vein?

A

Axillary vein is the main vein draining the upper limb, with contributions from the cephalic and basilic veins

28
Q

What do the axillary lymph nodes do and why are they clinically significant?

A
  • The axillary lymph nodes filter lymph that has drained from the upper limb and pectoral region
  • In women, axillary lymph node enlargement is a non-specific indicator of breast cancer
29
Q

What is the brachial plexus?

A

The brachial plexus is a network of nerve fibres that supplies the skin and musculature of the upper limb

30
Q

Describe the formation of the brachial plexus

A

The plexus is formed by the anterior rami (divisions) of the cervical spinal nerves C5, C6, C7 and C8, and the first thoracic spinal nerve, T1

31
Q

Describe the course of the brachial plexus

A
  • It begins in the root of the neck (anterior and medial scalene muscles)
  • It passes through the axilla region
  • It enters the upper arm
32
Q

How can the brachial plexus be divided?

A

The brachial plexus is divided into five parts: roots, trunks, divisions, cords and branches (no functional differences)

33
Q

What are the roots of the brachial plexus?

A

The roots refer the beginning of the brachial plexus, formed by the anterior divisions of the spinal nerves C5, C6, C7, C8 and T1

34
Q

What are the trunks of the brachial plexus

A

At the base of the neck, the roots converge to form three trunks:

- Superior trunk – a combination of C5 and C6 roots

  • Middle trunk – a continuation of C7
  • Inferior trunk – a combination of C8 and T1 roots
35
Q

What are the divisions of the brachial plexus?

A

Within the posterior triangle of the neck, each trunk divides into two branches:

  • The anterior division (3 nerve fibres)
  • The posterior division (3 nerve fibres)
36
Q

What are the cords of the brachial plexus?

A

Once the anterior and posterior divisions enter the axilla, they combine to form three cords:

  • The lateral cord (anterior divisions of superior & middle trunk)
  • The posterior cord (posterior divisions of all trunks)
  • The medial cord (anterior division of inferior trunk)
37
Q

What are the 5 major branches of the brachial plexus?

A
38
Q

Identify the roots of the musculocutaneous nerve

A

C5, C6, C7

39
Q

Describe the motor and sensory functions of the musculocutaneous nerve

A
  • Motor functions: innervates the brachialis, biceps brachii and coracobrachialis muscles
  • Sensory functions: innervates the lateral half of the anterior forearm, and a small lateral portion of the posterior forearm
40
Q

Identify the roots of the axillary nerve

A

C5 and C6

41
Q

Describe the motor and sensory functions of the axillary nerve

A
  • Motor functions: innervates the teres minor and deltoid muscles
  • Sensory functions: innervates the inferior region of the deltoid (regimental badge area)
42
Q

Identify the roots of the median nerve

A

C6 – T1 (also, contains fibres from C5 in some individuals)

43
Q

Describe the motor and sensory functions of the median nerve

A
  • Motor functions: innervates most of the flexor muscles in the forearm, the thenar muscles and the two lateral lumbricals for the index & middle fingers
  • Sensory functions: innervates the lateral part of the palm, the lateral 3 ½ fingers on the palmar surface
44
Q

Identify the roots of the radial nerve

A

C5-C8 and T1

45
Q

Describe the motor and sensory functions of the radial nerve

A
  • Motor functions: innervates the triceps brachii, and the extensor muscles in the posterior compartment of the forearm
  • Sensory functions: innervates the posterior aspect of the arm and forearm, and the posterior, lateral aspect of the hand
46
Q

Identify the roots of the ulnar nerve

A

C8 and T1

47
Q

Describe the motor and sensory functions of the ulnar nerve

A
  • Motor functions: innervates the muscles of the hand (apart from the thenar muscles and two lateral lumbricals), flexor carpi ulnaris and medial half of flexor digitorum profundus
  • Sensory functions: innervates the anterior and posterior surfaces of the medial 1 ½ fingers, and the associated palm area
48
Q

In terms of the branches of the brachial plexus, what are the motor compartments of the upper arm?

A
49
Q

What is long thoracic nerve palsy?

A
  • Long thoracic nerve palsy is a condition characterized by pain and loss of shoulder movement due to damage/injury of the long thoracic nerve
  • It presents with winged scapula as the serratus anterior is paralysed and the scapula is no longer held against the ribcage so protrudes out the back
50
Q

When does long thoracic nerve palsy commonly occur?

A

Long thoracic nerve palsy commonly occurs when upper limb is stretched violently (traction injuries)

51
Q

What is the clinical significance of axillary lymph nodes?

A

Approximately 75% of lymph from the breast drains into the axilla lymph nodes, so can be biopsied if breast cancer is suspected

52
Q

What is axillary clearance and what are its associated risks?

A
  • Axillary clearance is a procedure wherein the axillary nodes are removed to prevent breast cancer from spreading
  • During this procedure, the long thoracic nerve may become damaged, resulting in winged scapula
53
Q

What is Erb’s Palsy?

A

- Erb’s palsy is a condition resulting in the paralysis of the arm caused by injury to the upper brachial plexus (C5-C6)

  • It presents with waiter’s tip: affected limb hangs limply, medially rotated by pectoralis major and pronated due to the loss of biceps brachii
54
Q

Identify the various nerves affected and muscles paralysed in Erb’s palsy

A
  • Nerves affected: musculocutaneous, axillary, suprascapular and nerve to subclavius
  • Muscles paralysed: supraspinatus, infraspinatus, subclavius, biceps brachii, brachialis, coracobrachialis, deltoid and teres minor
55
Q

Identify the motor functions weakened and the sensation lost in Erb’s palsy

A

- Motor functions: shoulder abduction, lateral rotation, supination, shoulder flexion

- Loss of sensation: lateral side of arm

56
Q

When does Erb’s palsy commonly occur?

A

Erb’s palsy commonly occurs where there is excessive increase in the angle between the neck and shoulder (difficult birth or shoulder trauma)

57
Q

What is Klumpke’s Palsy?

A
  • Klumpke’s palsy is a condition resulting in the paralysis of the muscles of the forearm and hand caused by injury to the lower brachial plexus
  • The hand presents with a clawed appearance as the MCP joints are hyperextended and the IP joints are flexed
58
Q

Identify the 2 nerves affected by Klumpke’s palsy

A
  • Ulnar nerve
  • Median nerve
59
Q

Identify the muscles paralysed and describe sensation lost in Klumpke’s palsy

A
  • Muscles paralysed: small muscles of the hand (flexor muscles in the forearm are supplied by the ulna and median nerves, but are innervated by different roots)
  • Loss of sensation: medial side of arm
60
Q

When does Klumpke’s palsy commonly occur?

A

Klumpke’s palsy commonly results from excessive abduction of the arm e.g person catching a branch as they fall from a tree (lower incidence than Erb’s palsy)