Orbit muscles

Question 1

Extra ocular Muscles

Answer 1

Voluntary(skeletal) Muscles:7
1. Four Recti – Superior, inferior, medial and lateral.
2. Two Oblique – Superior & inferior.
3. Elevator of upper eyelid – Levator palpebrae superioris.

Involuntary(smooth) Muscles:3
1. Superior tarsal muscle – Deeper part of levator palpebrae superioris
2. Inferior tarsal muscle
3. Orbitalis muscle

Question 2

Superior rectus

Answer 2

O: upper part common tendinous ring and dural sheath of optic nerve
I:upper part of the sclera,
N: superior division oculomotor nerve
A:
abducted:elevation
adduction and intorsion in adducted position
clinical examination:

Question 3

Inferior rectus

Answer 3

o:common tendinous ring, below the optic canal.
I:obliquely into the sclera
N:branch of the inferior division of the oculomotor nerve
Actions:
in normal position: adduction,extorsion,depression
in adducted eyeball:extorsion
in abducted:deppresion

Question 4

Medial rectus

Answer 4

o:medial part of the common tendinous ring
I:medial surface of the sclera
N:ranch from the inferior division of the oculomotor nerve
Actions : adduction. The two medial recti acting together- convergence of eyes(part of near reflex)

Question 5

Lateral rectus

Answer 5

O:lateral part of the common tendinous ring,some fibres arise from aspine on the greater wing of the sphenoid.
I:lateral surface of the sclera

Question 6

Superior oblique

Answer 6

Origin: from the body of the Sphenoid, superomedial to the optic canal
I:sclera in the posterior part of the superolateral quadrant
N:trochlear nerve
A:
In primary position of eyeball: Abduction, Depression, Intorsion
In adducted eyeball:Depression only
In abducted eyeball:Intorsion only

clinical:adduct the eye first) then to ask look down or up. Only in adducted eye, the muscle axis and optic axis coinside

Question 7

Inferior oblique

Answer 7

O:orbital surface of the maxilla
I: sclera behind the equator to the
posterior part of the inferolateral quadrant
N:branch of the inferior division of the oculomotor nerve
A:
normal:Abduction ,Elevation ,Extorsion
adducted eyeball:elevation only
abducted eyeball: extorsion only

Question 8

LEVATOR PALPEBRAE SUPERIORIS

Answer 8

O:inferior aspect of the lesser wing of the sphenoid
The Superior lamina-skeletal muscle (voluntary), some fibres attach to the anterior surface of the tarsus, and the rest pierce the orbicularis Oculi for insertion to the skin of the upper eyelid.

Inferior lamina- smooth (involuntary) muscle -superior tarsal or Muller’s muscle , lying the underside of the superior lamina of LPS

N:branch of the superior division of the oculomotor nerve,smooth mucle has sympathetic fibres fr plexus around ICA

Actions:
Elevation of the upper eyelid.
opposed by the palpebral part of orbicularis oculi.

widening of the palpebral apertures seen due to contraction of the smooth muscle of the superior and inferior tarsal muscles as a result of increased sympathetic activity.

Lesions of the sympathetic supply result in drooping of the upper eyelid (ptosis), as seen in Horner’s syndrome.