Test 75    (Ocular anatomy)

1. The lacrimal gland:

a. is a S-shaped structure
b. is completely covered by orbital fat
c. has a orbital part which is larger than the palpebral part
d. is visible when the upper lid is everted
e. receives sympathetic supply from the greater petrosal 
    nerve

Answera.F   b.F  c.T   d.F   e.F
It is a C-shaped structure and is divided into 
two portions by the levator aponeurosis: a 
larger orbital part and a smaller palpebral part.
It is situated lateral to the orbital fat and may 
be easily confused with the central fat pad.
It receives sympathetic supply from the deep 
petrosal nerve.

2. The following are true about the superior oblique muscle:

a. it is supplied by the fourth cranial nerve on its upper 
   surface
b. it arises from the frontal bone superomedial to the 
    optic canal
c. it depresses the globe in adduction
d. it extorts the globe in the primary position
e. its paralysis causes hypodeviation

Answera.T   b.F   c.T   d.F   e.F
It arises from the sphenoid bone superomedial
to the optic canal.
It acts on the globe at an angle of 54 degrees to
the vertical plane. It intorts the globe.
Its paralysis is associated with hyperdeviation
due to unopposed action of the inferior oblique muscle.

3. The cornea:

a. has a greater diameter horizontally than vertically
b. is more curved vertically than horizontally
c. is more peripherally than centrally
d. has a refractive index of 1.36
e. has a greater radius of curvature anteriorly than 
    posteriorly

Answera.T   b.T   c.F   d.T   e.T
The radius of curvature for the anterior cornea
is about 7.8 mm whereas that for the posterior 
cornea is about 6.5mm.

4. The following are true about the canaliculus:

a. it contains a shorter vertical portion and a longer 
    horizontal portion
b. the upper canaliculus is longer than the lower 
   canaliculus
c. the upper canaliculus has a greater lumen than the 
    lower canaliculus
d. it is lined by columnar cells
e. the common canaliculus pierces the lacrimal sac 
    about 4 mm below the apex

Answera.T  b.F  c.F   d.F   e.F
The upper canaliculus is shorter than the lower 
canaliculus
The lumen of the upper and lower canaliculus 
is about the same size of about 0.5 mm diameter.
It is lined by stratified squamous epithelium.

5. The inferior oblique muscle:

a. arises from sphenoid
b. extorts the globe
c. receives blood supply from the ophthalmic and 
    infraorbital arteries
d. passes anterolaterally beneath the inferior rectus to its 
    insertion
e. attaches to the sclera about 2 mm from the fovea
 

Answera.F   b.T   c.T   d.F   e.T
It arises from the maxilla.
Its actions are elevation, extortion and abduction.
It passes anterolaterally beneath the inferior rectus.

 
 

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