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Year 2 DO Diploma Revision > Extrinsic Ocular Muscles > Flashcards

Extrinsic Ocular Muscles Flashcards

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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
Q

Angle to Horizontal Plane: Medial Rectus

A

Attached along horizontal plane

26
Q

Angle to Sagittal Plane: Lateral Rectus

A

51 degrees

27
Q

Blood Supply: Superior Rectus

A

Superior muscular branch of ophthalmic artery

Superior ophthalmic vein

28
Q

Blood Supply: Inferior Rectus

A

Inferior muscular branch of ophthalmic artery & and infraorbital artery

Inferior ophthalmic vein

29
Q

Blood Supply: Medial Rectus

A

Inferior muscular branch of ophthalmic artery

Inferior ophthalmic vein

30
Q

Blood Supply: Lateral Rectus

A

Superior muscular branch of ophthalmic artery and lacrimal artery

Inferior ophthalmic vein

31
Q

Blood Supply: Superior Oblique

A

Superior muscular branch of ophthalmic artery

Superior ophthalmic vein

32
Q

Blood Supply: Inferior Oblique

A

Inferior muscular branch of ophthalmic artery and infra orbital artery

Inferior ophthalmic vein

33
Q

Nerve Supply: Superior Rectus

A

Superior division of Oculomotor Nerve - CN 3

34
Q

Nerve Supply: Inferior Rectus

A

Inferior division of Oculomotor Nerve - CN 3

35
Q

Nerve Supply: Medial Rectus

A

Inferior division of Oculomotor Nerve - CN 3

36
Q

Nerve Supply: Lateral Rectus

A

Abducent Nerve - CN 6

37
Q

Nerve Supply: Superior Oblique

A

Trochlea Nerve - CN 4

38
Q

Nerve Supply: Inferior Oblique

A

Inferior division of Oculomotor Nerve - CN 3

39
Q

Location of Centre of Rotation

A

13-14mm behind apex of cornea and 1.65mm inset nasally from geometric centre

40
Q

Primary position of the Eyes

A

Primary position is when they’re fixated on a distant object.

41
Q

Direction of: Supraduction

A

Up

42
Q

Direction of: Infraduction

A

Down

43
Q

Direction of: Adduction

A

In

44
Q

Direction of: Abduction

A

Out

45
Q

Direction of: Incycloduction

A

Rotates In

46
Q

Direction of: Excycloduction

A

Rotates Out

47
Q

Muscle’s Action (Primary and Secondary): Superior Rectus

A

Supraduction, Adduction & Incycloduction

48
Q

Muscle’s Action (Primary and Secondary): Inferior Rectus

A

Infraduction, Adduction & Excycloduction

49
Q

Muscle’s Action (Primary and Secondary): Medial Rectus

A

Adduction

50
Q

Muscle’s Action (Primary and Secondary): Lateral Rectus

A

Abduction

51
Q

Muscle’s Action (Primary and Secondary): Superior Oblique

A

Infraduction, Incycloduction & Abduction

52
Q

Muscle’s Action (Primary and Secondary): Inferior Oblique

A

Supraduction, Excycloduction & Abduction

Year 2 DO Diploma Revision (10 decks)

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