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Year 2 DO Diploma Revision > Extrinsic Ocular Muscles > Flashcards

Extrinsic Ocular Muscles Flashcards

1
Q

Function of the EOMs

A

To produce precise and coordinating eye movements and maintaining binocular vision.

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2
Q

What connects the muscles to the eye and where?

A

Distal tendons attach to the scleral stroma

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3
Q

Origin: Superior Rectus

A

Annulus of Zinn in apex of orbit

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4
Q

Origin: Inferior Rectus

A

Annulus of Zinn in apex of orbit

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5
Q

Origin: Medial Rectus

A

Annulus of Zinn in apex of orbit

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6
Q

Origin: Lateral Rectus

A

Annulus of Zinn in apex of orbit

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7
Q

Origin: Superior Oblique

A

Apex of orbit – superior and nasal to Annulus of Zinn

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8
Q

Origin: Inferior Oblique

A

Lacrimal foramen

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9
Q

5 features of the EOMs

A

1) Straited muscle – Fibrillenstruktur and Felderstruktur
2) High level of nervous control (CN 3, 4 and 6)
3) Thinner than skeletal cells (10-15 um in diameter)
4) Very active cells means very rich blood supply
5) Cells extended full length of muscle (about 40um)

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10
Q

4 nervous control features of the EOMs

A

1) 1 motor neuron controls 3-10 muscles cells vs 1000 in general skeletal
2) En plaque stimulate fast twitch fibres for rapid eye movements
3) En grape stimulates tonic fibres for smoother eye movements and fixation
4) Extensive presence of proprioceptors

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11
Q

Distance from insertion to limbus: Superior Rectus

A

7.5mm

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12
Q

Distance from insertion to limbus: Inferior Rectus

A

6.5mm

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13
Q

Distance from insertion to limbus: Medial Rectus

A

5.5mm

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14
Q

Distance from insertion to limbus: Lateral Rectus

A

7mm

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15
Q

Distance from equator to insertion: Superior Oblique

A

6mm

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16
Q

Distance from equator to insertion: Inferior Oblique

A

Level with posterior pole

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17
Q

Muscle Length: Superior Rectus

A

42mm (longest rectus)

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18
Q

Muscle Length: Inferior Rectus

A

40mm (shortest rectus)

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19
Q

Muscle Length: Medial Rectus

A

41mm

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20
Q

Muscle Length: Lateral Rectus

A

41mm

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21
Q

Muscle Length: Superior Oblique (inc tendon)

A

60-65mm (longest EOM)

22
Q

Muscle Length: Inferior Oblique (inc tendon)

A

37mm (shortest EOM)

23
Q

Angle to Sagittal Plane: Superior Rectus

A

23 degrees

24
Q

Angle to Sagittal Plane: Inferior Rectus

A

23 degrees

25
Angle to Horizontal Plane: Medial Rectus
Attached along horizontal plane
26
Angle to Sagittal Plane: Lateral Rectus
51 degrees
27
Blood Supply: Superior Rectus
Superior muscular branch of ophthalmic artery Superior ophthalmic vein
28
Blood Supply: Inferior Rectus
Inferior muscular branch of ophthalmic artery & and infraorbital artery Inferior ophthalmic vein
29
Blood Supply: Medial Rectus
Inferior muscular branch of ophthalmic artery Inferior ophthalmic vein
30
Blood Supply: Lateral Rectus
Superior muscular branch of ophthalmic artery and lacrimal artery Inferior ophthalmic vein
31
Blood Supply: Superior Oblique
Superior muscular branch of ophthalmic artery Superior ophthalmic vein
32
Blood Supply: Inferior Oblique
Inferior muscular branch of ophthalmic artery and infra orbital artery Inferior ophthalmic vein
33
Nerve Supply: Superior Rectus
Superior division of Oculomotor Nerve - CN 3
34
Nerve Supply: Inferior Rectus
Inferior division of Oculomotor Nerve - CN 3
35
Nerve Supply: Medial Rectus
Inferior division of Oculomotor Nerve - CN 3
36
Nerve Supply: Lateral Rectus
Abducent Nerve - CN 6
37
Nerve Supply: Superior Oblique
Trochlea Nerve - CN 4
38
Nerve Supply: Inferior Oblique
Inferior division of Oculomotor Nerve - CN 3
39
Location of Centre of Rotation
13-14mm behind apex of cornea and 1.65mm inset nasally from geometric centre
40
Primary position of the Eyes
Primary position is when they’re fixated on a distant object.
41
Direction of: Supraduction
Up
42
Direction of: Infraduction
Down
43
Direction of: Adduction
In
44
Direction of: Abduction
Out
45
Direction of: Incycloduction
Rotates In
46
Direction of: Excycloduction
Rotates Out
47
Muscle's Action (Primary and Secondary): Superior Rectus
Supraduction, Adduction & Incycloduction
48
Muscle's Action (Primary and Secondary): Inferior Rectus
Infraduction, Adduction & Excycloduction
49
Muscle's Action (Primary and Secondary): Medial Rectus
Adduction
50
Muscle's Action (Primary and Secondary): Lateral Rectus
Abduction
51
Muscle's Action (Primary and Secondary): Superior Oblique
Infraduction, Incycloduction & Abduction
52
Muscle's Action (Primary and Secondary): Inferior Oblique
Supraduction, Excycloduction & Abduction

Year 2 DO Diploma Revision (9 decks)

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