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ACEM Primary Written > Musculoskeletal: Anatomy - Brachial plexus and myotomes > Flashcards

Musculoskeletal: Anatomy - Brachial plexus and myotomes Flashcards

1
Q

Describe the course of brachial plexus

A

Roots: pass between anterior and middle scalene muscles with subclavian artery, form trunks at base of neck
Trunks: traverse the posterior triangle of neck, separates into anterior and posterior divisions on passing through cervico-axillary canal posterior to clavicle and outer border of first rib
Cords: on entering axilla, associated with second part of axillary artery as indicated by names (e.g. lateral is lateral to artery)
Branches: at lateral axilla

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2
Q

Draw and label the brachial plexus

A
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3
Q

Name the supraclavicular branches of the brachial plexus

A
  1. Dorsal scapular
  2. Long thoracic
  3. Suprascapular
  4. Subclavian nerve
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4
Q

Origin, course, and structures innervated by dorsal scapular n.

A

Origin: C5 +/- C4
Course: pierces middle scalene, descends deep to levator scapular and rhomboids
Structures: rhomboids +/- levator scapulae

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5
Q

Origin, course, and structures innervated by long thoracic n.

A

Origin: C5-7
Course: through cervico-axillary canal, runs on serratus anterior
Structures: serratus anterior

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6
Q

Origin, course, and structures innervated by suprascapular n.

A

Origin: superior trunk (C5-6 +/- C4)
Course: posterior triangle of neck, through scapular notch inferior to superior transverse scapular ligament
Structures: supraspinatus, infraspinatus, glenohumeral joint

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7
Q

Origin, course, and structures innervated by subclavian nerve

A

Origin: superior trunk (C5-6 +/- C4)
Course: posterior to clavicle and anterior to brachial plexus and subclavian artery, may give off accessory root to phrenic nerve
Structures: subclavius and sternoclavicular joint (accessory phrenic root nerve innervates diaphragm)

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8
Q

Name the infraclavicular nerves of the brachial plexus

A
  1. Lateral pectoral
  2. Musculocutaneous
  3. Median
  4. Medial pectoral
  5. Medial cutaneous nerve of arm
  6. Medial cutaneous nerve of forearm
  7. Ulnar
  8. Upper subscapular
  9. Lower subscapular
  10. Thoracodorsal
  11. Axillary
  12. Radial
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9
Q

Origin, course, and structures innervated by lateral pectoral n.

A

Origin: lateral cord (C5-7)
Course: pierces costocoracoid membrane to reach deep pectoral muscles, communicating branch to medial pectoral nerve passes anterior to axillary nerve/vein
Structures: primarily pec major (some to pec minor via communicating branch)

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10
Q

Origin, course, and structures innervated by musculocutaneous n.

A

Origin: terminal branch of lateral cord (C5-7)
Course: exits axilla piercing coracobrachialis, descends between biceps brachii and brachialis, continues as lateral cutaneous nerve of forearm
Structures: arm flexors, skin of lateral aspect of forearm

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11
Q

Origin, course, and structures innervated by median n.

A

Origin: terminal branch of lateral (lateral root of median n., C6-7) and medial (medial root of median n., C8-T1) cords
Course: roots merge lateral to axillary artery, descends through arm adjacent to brachial artery then crosses anteriorly to lie medial to artery in cubital fossa
Structures: forearm flexors except FCU and medial FDP, thenar muscles and lateral lumbricals, skin of lateral palm and 3.5 fingers anteriorly

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12
Q

What are the branches of the medial cord? What roots do they receive fibres from?

A
  1. Medial pectoral (C8-T1)
  2. Medial cutaneous nerve of arm (C8-T1)
  3. Medial cutaneous nerve of forearm (C8-T1)
  4. Medial root of median nerve (terminal branch: C8-T1)
  5. Ulnar (larger terminal branch: C8-T1 +/- C7)
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13
Q

Origin, course, and structures innervated by medial pectoral n.

A

Origin: medial cord (C8-T1)
Course: between axillary artery and vein, pierces pec minor and enters deep surface pec major, is LATERAL to lateral pectoral n.
Structures: pec minor, sternocostal part of pec major

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14
Q

Origin, course, and structures innervated by medial cutaneous n. of arm

A

Origin: medial cord (C8-T1)
Course: medial to axillary and brachial veins, communicates with intercostobrachial nerve
Structures: skin of medial arm to medial epicondyle and olecranon

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15
Q

Origin, course, and structures innervated by medial cutaneous n. of forearm

A

Origin: medial cord (C8-T1)
Course: initially with ulnar nerve, pierces deep fascia with basilic vein and enters subcut tissue, divides into anterior and posterior branches
Structures: skin of medial forearm to wrist

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16
Q

Origin, course, and structures innervated by ulnar n.

A

Origin: terminal branch of medial cord (C8-T1 +/- C7)
Course: medial arm, posterior to medial epicondyle (“funny bone”), descends ulnar aspect of forearm to hand
Structures: FCU and medial FDP, intrinsic muscles of hand excluding those innervated by median n., skin of medial 1.5 digits (anterior and posterior)

17
Q

Origin, course, and structures innervated by upper subscapular n.

A

Origin: side branch of posterior cord (C5)
Course: posterior to enter subscapularis
Structures: superior subscapularis

18
Q

What are the branches of the posterior cord? What roots do they receive fibres from?

A
  1. Upper subscapular (C5)
  2. Lower subscapular (C6)
  3. Thoracodorsal (C6-8)
  4. Axillary (terminal branch: C5-6)
  5. Radial (terminal branch: C5-T1)
19
Q

What are the branches of the lateral cord? What roots do they receive fibres from?

A
  1. Lateral pectoral (C5-7)
  2. Musculocutaneous (terminal branch: C5-7)
  3. Lateral root of median nerve (terminal branch: C6-7)
20
Q

Origin, course, and structures innervated by lower subscapular n.

A

Origin: side branch of posterior cord (C6)
Course: inferolateral deep to subscapular artery/vein
Structures: inferior subscapularis, teres major

21
Q

Origin, course, and structures innervated by thoracodorsal n.

A

Origin: side branch of posterior cord (C6-8)
Course: arises between upper and lower subscapular nerves, runs inferolaterally along posterior axillary wall to apical part of lat dorsi
Structures: lat dorsi

22
Q

Origin, course, and structures innervated by axillary n.

A

Origin: terminal branch of posterior cord (C5-6)
Course: exits axillary fossa posteriorly, passes through quadrangular space with posterior circumflex humeral artery, gives rise to superior lateral brachial cutaneous nerve, winds around surgical neck of humerus deep to deltoid
Structures: glenohumeral joint, teres minor, deltoid, skin of superolateral arm (over inferior deltoid: regimental badge)

23
Q

Origin, course, and structures innervated by radial n.

A

Origin: larger terminal branch of posterior cord (C5-T1)
Course: exits axillary fossa posterior to axillary artery, travels in radial groove with deep brachial artery between lateral and medial heads of triceps, perforates lateral intermuscular septum and enter cubital fossa, divides in superficial (cutaneous) and deep (motor) radial nerves
Structures: arm and forearm extensors, skin of posterior and inferolateral arm, skin of posterior forearm, skin of dorsum of hand lateral to axial line of digit 4 (and excluding distal digits)

24
Q

What is the largest branch of the brachial plexus?

A

Radial n.

25
Q

What are the borders of the quadrangular space?

A

Superior: subscapularis, head of humerus, teres minor
Medial: long head of triceps
Lateral: coracobrachialis, surgical neck of humerus
Inferior: teres major

26
Q

What nerves supply the scalenes and longus colli muscles?

A

Unnamed muscular branches arising from anterior rami of C5-T1

27
Q

How many branches does each cord have?

A

Lateral: 3
Posterior: 5
Medial: 5

28
Q

Outline the upper limb myotomes

A

Shoulder abd, lateral rotation and flex: C5
Shoulder add, medial rotation and ext: C6-8
Elbow flex: C5-6
Elbow ext: C6-7
Wrist flex and ext: C6-7
Wrist supination: C6
Wrist pronation: C7-8
Digit flex and ext: C7-8
Digit abd and add: T1
Opposition: T1 (small component C8)

ACEM Primary Written (150 decks)

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