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Anatomy of the Individual > Muscular Variation > Flashcards

Muscular Variation Flashcards

1
Q

What is the 1st muscle/nerve law?

A

Migration:

  • Nerve regarded as indicator of the route the muscle mass migrated along
  • eg. Diaphragm
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2
Q

What is the 2nd muscle/nerve law?

A

Fusion:

  • When muscle is supplied by 2 different nerves
  • Fusion of 2 masses; each with own innervation
  • eg. External oblique supply upper and lower
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3
Q

What is the 3rd muscle/nerve law?

A

Separation:

  • Two different muscle masses supplied by same nerve
  • Derived from a single mass
  • eg. SCM and trapezius
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4
Q

What is the reference for the muscle/nerve laws?

A

Shinohara, 1996

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5
Q

What variant of palmaris longus did John Wood describe in the 1880s?

A

A ‘new’ muscle which flexed 3rd metacarpal:

  • Flexor carpi radialis seu profundus
  • Arose from radius below FDP
  • Inserts into 3rd metacarpal OR 2nd metacarpal and trapezium/palmar fascia
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6
Q

What other variations were noted in the patient that John Wood studied in the 1880s?

A

Flexor carpi radialis also attached to 4th metacarpal
Extra extensor to middle finger
2x extensor digiti minimi plus slip to ring finger
Slip of fibularis brevis to little toe

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7
Q

What was the hypothesis proposed by Smith et al., (2009) regarding the vastus medialis?

A

Is it:
- One single muscle
OR
- Vastus medialis obliquus (distally) and vastus medialis longus (proximally)

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8
Q

What participants were used in the study by Smith et al., (2009)?

A

699 healthy knees

591 knees with patellofemoral dysfunction

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9
Q

What do most of the knees in the Smith et al., (2009) study show?

A

Substantial variation in fibre alignment from proximal to distal

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10
Q

What variation was seen in a small proportion of both groups in the Smith et al., (2009) study?

A

A fibrofascial plane dividing the two ‘muscles’ of vastus medialis

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11
Q

What number of nerve branches were seen in both cohorts in the Smith et al., (2009) study?

A

1 or 2

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12
Q

What did Smith et al., (2009) conclude needs more studying?

A

Patellar instability

Anterior knee pain

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13
Q

Before 1977, what was the consensus on how muscles formed?

A

Somites gave rise to body wall muscles

Local cells in limbs formed limb muscles

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14
Q

What did Christ et al., (1977) suggest result in limb muscle formation?

A

Muscle forming cells left somites and migrated into limb buds
Underwent transition to mesenchyme

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15
Q

What do we now know all trunk muscles develop from?

A

Somites (dorsal dermomyotome)

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16
Q

What are hypaxial muscles?

A

Muscles ventral to horizontal septum of vertebrae:

  • Diaphragm
  • Abdominal muscles
  • All limb muscles
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17
Q

What are epaxial muscles?

A

Muscles dorsal to horizontal septum of vertebrae:

  • Erector spinae
  • Transversospinalis
  • Splenius
  • Suboccipital muscles
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18
Q

From where do hypaxial and epaxial muscles form?

A

All hypaxial muscles form from lateral 1/3 of somite

The remainder of the somite forms the epaxial muscles

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19
Q

Hypaxial muscles must translocate to their final destination. Precursors for what muscles extend into the lateral plate mesoderm?

A

Pre-vertebral muscles
Intercostal muscles
Abdominal muscles

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20
Q

Hypaxial muscles must translocate to their final destination. Where do limb muscles translocation from?

A

Ventrolateral lip of dermomyotome

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21
Q

Where do limb muscle precursors translocate to and what do they transition to?

A

Transition to mesenchmye

Precursors migrate to limbs

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22
Q

What is the final step in the simplified view of development?

A

Cells move directly from origin to destination:

- Not true for some muscles

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23
Q

Why was the in-out mechanism propsed?

A

Some muscles originate on body wall and insert into limbs (eg. pec major):

  • How do they form?
  • Why do some cells remain in trunk and others move into limbs
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24
Q

What is the in-out mechanism?

A
  1. Myogenic cells from somites migrate as individual cells to limb buds
  2. A cohort of MyoD-expressing cells migrate back to trunk
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25
Q

What does the in-out mechanism imply muscle development relies on?

A

Limb development

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26
Q

What are references for the in-out mechanism?

A

Valasek et al., (2005)

Evans, (2006)

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27
Q

What models are used to investigate the in-out mechanism?

A

Mammalian and avian models

Perineal and pectoral girdle muscles

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28
Q

What pectoral muscles attach to the axial skeleton but the main muscle bulk lies outwith limb?

A

Pectoralis major

Latissimus dorsi

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29
Q

How do pectoral muscles form?

A
  1. Precursors start by migrating to forelimb (upper limb bud)
  2. Some cells stay in limb bud = Insertion sites
  3. Many MyoD-differentiated cells move back to trunk = Main muscle bulk
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30
Q

How does the nerve supply to pectoral muscles form?

A

From brachial plexus:

  • Initially extend into limb bud
  • Then extend onto body wall
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31
Q

Regarding the pectoral region, what muscle formation is seen in mutant mice?

A 
Superficial muscles don't form
Deeper muscles do form:
- Serratus anterior
- Supraspinatus
Muscle formation without migration for some muscles between trunk and limbs
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32
Q

What is Poland’s syndrome?

A

Absence of pectoralis major and serratus anterior

Syndactyly

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33
Q

What variations were noted on the left side of the cadaver in a case study by Mosconi and Kamath, (2003)?

A

Sternal portion of sternocostal head of pec. major absent
Rest of pec. major well developed
Normal pec. minor

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34
Q

What variations were noted on the right side of the cadaver in a case study by Mosconi and Kamath, (2003)?

A 
Entire pec. major absent
Muscles infiltrated by connective tissue and fat:
- Pec. minor
- Deltoid
- Coracobrachialis
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35
Q

What variations were noted on both sides of the cadaver in a case study by Mosconi and Kamath, (2003)? What does this suggest?

A

Lateral pectoral nerves absent
Medial pectoral nerves present
Suggests developmental failure of embryonic muscles:
- Rather than secondary to polio or Poland’s syndrome

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36
Q

What is the development of pec. major and minor?

A

Develop from a muscle mass during 5th month in utero

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37
Q

How does pec major develop?

A

Attaches to clavicle
Then fans out to attach to:
- Ribs
- Sternum

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38
Q

What is the textbook anatomy of flexor digitorum superficialis?

A 
Origins:
- Medial epicondyle
- Radius
Insertion = Middle phalanx of digits 2-5
Innervated by median nerve
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39
Q

Where do most flexor digitorum superficialis anomalies arise?

A

To ring and little fingers

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40
Q

How does flexor digitorum superficialis develop?

A

As a single mass (palm or forearm) and develops
OR
As dual origin with palmar mass migrating to join mass in forearm

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41
Q

Regarding the flexor digitorum superficialis, what variation did Kobayashi et al., (2003) note?

A

Mass in center of flexor retinaculum inserts into middle phalanx of little finger - Split tendon
Normal little finger slip of antebrachial FDS absent

42
Q

What is extensor digitorum brevis manus?

A

A muscle mass:

  • From dorsal wrist carpals
  • Inserts into extensor hood of index/middle finger
43
Q

What is extensor digitorum brevis manus also called?

A

Extensor indicis brevis

Extensor medii brevis

44
Q

What is extensor digitorum brevis manus usually innervated by?

A

Posterior interosseous nerve (radial nerve branch)

45
Q

What is the prevalence of extensor digitorum brevis manus according to Rodriguez-Niedenfuhr et al., (2002)?

A

Seen in 162 hands out of 8111 (2%)

46
Q

What is extensor digitorum brevis manus associated with?

A

Absence of extensor indicis

47
Q

What might the extensor digitorum brevis manus be a derivative of?

A 
Interosseous muscles (Wood, 1864)
Dorsal forearm (Kaneff, 1970)
48
Q

What might extensor digitorum brevis manus be a homologue of?

A

Extensor digitorum brevis in the foot

49
Q

What does the innervation to extensor digitorum brevis manus suggest?

A

It’s a forearm derivative

50
Q

What can extensor digitorum brevis manus be mistaken for?

A

Ganglia
Extensor synovitis
Tendon sheath cyst
Soft tumour

51
Q

How can extensor digitorum brevis manus be differentiated from a ganglion?

A

EDBM prominent during wrist/digit extension

Ganglion prominent during wrist/digit flexion

52
Q

What is sternalis?

A

Anterior thoracic muscle that lies superficial to:

  • Sternum
  • Sternocostal fascicles of pectoralis major
53
Q

Is sternalis usually unilateral or bilateral?

A

Often bilateral:

- May have >1 on each side

54
Q

Regarding sternalis, what did the case study by Arraez-Aybar et al., (2003) show?

A

Sternalis in left hemithorax of 70 male cadaver:
- 13cm long
- 7cm wide
- 0.5cm thick
Innervated by branch of left 4th intercostal nerve

55
Q

What does Turner, (1867) suggest is the origin of sternalis?

A

Pectoralis cutaneous muscle of lower animals

56
Q

What does Barlow, (1934) suggest is the origin of sternalis?

A

Remains of panniculus carnosis:

- Playtsma in humans

57
Q

What does Clemente, (1985) suggest is the origin of sternalis?

A

Misplaced pectoralis minor

58
Q

What does Saddler, (1995) suggest is the origin of sternalis?

A

Longitudinal column from ventral tips of hypomere:

- Portion of myotome that forms muscles of body wall

59
Q

What is the innervation to sternalis?

A

55% from internal and external thoracic nerves
43% from intercostal nerves
2% from both

60
Q

What issues can sternalis cause

A

ECG alterations
Mistaken for herniated pectoral muscles
Mistaken for soft tissue mass - Mammography

61
Q

What is the textbook structure of plantaris?

A

Originates from lateral condyle of femur above lateral head of gastrocnemius
Long tendon joints tendocalcaneus
Plantarflexes ankle

62
Q

Regarding plantaris, what did Freeman et al., (2008) find?

A

Studied 46 knees:

  • 26 conformed to standard definitions
  • 6 had absent plantaris
  • 14 had variations
63
Q

What variations of plantaris did Freeman et al., (2008) find?

A

9 with interdigitations with lateral head of gastrocnemius

5 showed a strong fibrous extension to patella

64
Q

What do the plantaris variations found by Freeman et al., (2008) suggest?

A

Plantaris assists with lateral head of gastrocnemius

It is involved with patellofemoral dynamics

65
Q

What is the prevalence of an axillary arch?

A

7-8%

66
Q

What is the course of the axillary arch?

A

Runs from anterior border of latissimus dorsi to posterior layer of pectoralis major tendon

67
Q

What variations of axillary arch exist?

A

Can run to coracoid process

Can arise from serratus anterior

68
Q

Where does the axillary arch pass through and over?

A

All pass through axilla

Often pass over axillary NVB

69
Q

What is the prevalence of pectoralis quartis?

A

11-16%

70
Q

Where does pectoralis quartis arise?

A

From costochondral junction of 5th-6th rib
OR
Lateral margin of pectoralis major

71
Q

Where does pectoralis quartis extend along and insert?

A

Extends along lateral margin of pectoralis major
Inserts:
- Deep layer of pectoralis major tendon
- May insert into axillary arch

72
Q

Where does pectoralis quartis course in relation to the axillary NVB?

A

Passes over axillary NVB

73
Q

What is the prevalence of chondroepitrochlearis?

A

0.5% (Flaherty et al., 1999)

Most studies say it is rarer

74
Q

What is the course of chondroepitrochlearis?

A 
Long muscular band from:
- Costal cartilages OR
- Aponeurosis of external oblique
Insertions:
- Distal humerus
- Medial epicondyle of humerus
75
Q

What structure does chondroepitrochlearis cross?

A

Axilla

76
Q

How can anomalous muscular structures impact surgery?

A

Obscures view
Prevents access
Mistaken for other structures

77
Q

What techniques are often affected more by anomalous structures?

A

Laparoscopic

78
Q

Why are muscular anomalies often a ‘surprise’ during surgery?

A

Not seen on:
- Plain x-ray
- Angiogram
May be very small on CT

79
Q

What did Natsis et al., (2010) study?

A

Anomalous muscles which affect axillary lymph clearance

80
Q

What variations did Natsis et al., (2010) note in a 107 cadaver study?

A

8 cadavers (7.48%) affected by variations:
- Axillary arch in 5
- Pectoralis quartis in 3
- 1 with both
1 cadaver:
- Almost completely absent pec major on one side
- Both pec minors absent

81
Q

What was the conclusion of the Natsis et al., (2010) study?

A

Anomalies obscure surgical field of view

82
Q

What can additional slips of muscle/tendon impede? What can an accessory head of FPL compress?

A

Normal passage of nerves and blood vessels

AHFPL can entrap anterior interosseous nerve

83
Q

What are the origins of the accessory head of flexor pollicis longus referred to as Gantzer’s muscle?

A

Coronoid process
OR
Medial epicondyle

84
Q

What percentage of accessory head of FPL cases are Gantzer’s muscle?

A

50-60%

85
Q

What is the prevalence of accessory head of FPL?

A

5.3-75%

86
Q

What is the relation of the anterior interosseous nerve (which supplies FHL) to an accessory head of FPL in an Indian population? (Reference?)

A 
AIN anterior to AHFPL = 13.4%
AIN lateral to AHFPL = 65.8%
AIN posterior to AHFPL = 8.1%
AIN posterolateral to AHFPL = 12.8%
(Mahakkanukrah et al., 2004)
87
Q

What is the function of FPL?

A

Stabilises thumb in precision movement

88
Q

What can anterior interosseous nerve entrapment result in?

A

Neuralgic amyotrophy neuritis

89
Q

Where does the ulnar nerve run in relation to the carpal tunnel?

A

Above it

90
Q

What does the ulnar nerve run within to enter the hand?

A

Guyon’s/Ulnar canal

91
Q

What fibrous arch did Bozkurt et al., (2005) note was an additional structure in Guyon’s canal? What originated from this arch?

A

Fibrous arch from hook of hamate to pisiform in 21/37 upper limbs:
- In 13 of these, flexor digiti minimi originated from arch

92
Q

What addition muscles were noted in the study by Bozkurt et al., (2005)? How many ran through Guyon’s canal?

A

6 additional muscles:
- 5 accessory abductor digiti minimi
- 1 accessory flexor digiti minimi
4 passed through Guyon’s canal

93
Q

How can the axillary arch cause neurovascular compression?

A

If it passes through axillary NVB

94
Q

Telisky and Olinger, (2011) describe a variant case of axillary arch. What unique attachments did this axillary arch display?

A

Unique attachments to latissimus dorsi:

  • Medial fibres of arch in same direction as LD (typical for axillary arch)
  • Unique fibres at lateral edge of arch which curled laterally and inserted onto LD tendon
95
Q

What did the unique course of the axillary arch in the case study by Telisky and Olinger, (2011) affect anatomically?

A

‘Cradled’ axillary NVB:

  • Compression of NVB
  • Reduced space in axilla
96
Q

What were the dimensions of the axillary arch in the case study by Telisky and Olinger, (2011)?

A
  1. 5cm long
  2. 5cm wide
  3. 5cm thick
97
Q

After interviewing relatives, what did Telisky and Olinger, (2011) discover the unique attachments of the axillary arch in their case had caused?

A

Numbness and tingling in left arm for most of life
No vascular issues in left arm
No issues with right arm:
- Variation only seen on left side

98
Q

What is the summary of findings in the Provyn et al., (2011)?

A

Mean age 21.3 years
20 (out of 239 subjects) had axillary arch:
- 12 unilateral
- 8 bilateral

99
Q

Following echo doppler of axillary vessels of normal and axillary arch cohorts, what effects on axillary artery blood flow were noted between the groups by Provyn et al., (2011)?

A

No difference in blood flow

100
Q

Following echo doppler of axillary vessels of normal and axillary arch cohorts, what effects on axillary artery circulation velocity were noted between the groups by Provyn et al., (2011)?

A

Varied significantly with arm at:

  • 90 degrees abduction
  • 120 abduction
101
Q

Following echo doppler of axillary vessels of normal and axillary arch cohorts, what effects on axillary artery vessel diameter were noted between the groups by Provyn et al., (2011)?

A

Varied significantly with arm at:

  • 90 degrees abduction and exorotation
  • 120 abduction
102
Q

Following echo doppler of axillary vessels of normal and axillary arch cohorts, what effects on the axillary vien were noted between the groups by Provyn et al., (2011)?

A

No significant differences

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