Special Senses Practical

Question 2

on the left side of the specimen identify the structures marked with coloured pins

Answer 2

green - rectus muscles

blue - lacrimal gland

Question 3

what is the structure between the green pins

Answer 3

the optic nerve

Question 6

is the 3rd eyelid the true eyelid

Answer 6

no

Question 7

the ocular muscles have been pinned out on the perspex sheets

identify the

rectus muscles - lateral, dorsal, medial, ventral

ventral oblique muscles

dorsal oblique muscles

remaining parts of retractor bulbi

optic nerve

Answer 7

Question 8

what is the shape of the cartilage that supports the 3rd eyelid

Answer 8

T

Question 9

which muscle draws the eyeball caudally

Answer 9

retractor bulbi

Question 11

which muscle does not originate in the area of the optic canal? where does it originate?

Answer 11

ventral oblique –> originates from the ventromedial orbital wall

Question 12

what is the purpose of the trochlea for the dorsal oblique muscle

Answer 12

act as a pulley to change the direction of draw of the muscle

Question 13

what is the presumed function of the oblique muscles

Answer 13

resist axial rotation of the eyeball during movement

Question 14

what nerve(s) innervate the ocular muscles

Answer 14

oculomotor nerve (III) - dorsal rectus, medial rectus, ventral rectus, ventral oblique, part of retractor bulbi

trochlear nerve (IV) - dorsal oblique

trochlear nerve (IV) - dorsal oblique

abducent nerve (VI) - lateral rectus, retractor bulbi

Question 15

on eyeball specimens identify

cornea, sclera, iris, ciliary body, ciliary processes, pupil, tapetum, optic nerve, limbus, anterior chamber, posterior chamber, vitreous chamber

Answer 15

Question 16

what is the deviation of one eyeball called

Answer 16

strabismus

Question 17

on the scan identify the following structures –> tympanic bulla, epitympanic recess, external (horizontal) ear canal, semicircular canals, cochlea, tympanic membrane, internal acoustic meatus and course of vestibulocochlear nerve

Answer 17

Question 18

identify the structures of the ear on this MRI

Answer 18

Question 19

what is abnormal in this scan

which is the diseased ear and why

Answer 19

the right ear is diseased

instead of black gas, the right tympanic bulla contains material that appears white –> fluid

this is consistent with inflammation of the middle ear (otitis media)

Question 20

what is nystagmus

Answer 20

slow-quick flicking of the eyeball in association with rotating head movement –> also seen with diziness and disorders of the vestibular system

Question 21

what is causing the problem

Answer 21

there is a mass lying ventral to the eyeball and causing the displacement of eye

mass could be a tumour or an abscess caused by bacterial infection

abscessed behind the eye frequently associated with disease of the teeth –> esp true in rabbits

Question 22

in the black head, identify the zygomatic salivary gland

what effect would enlargement of this gland (because of a tumour) have?

Answer 22

exophthalmos - the eyeball would be displaced out of the orbit and would be seen protruding on clincal examination

Question 24

what is the function of the tapetum

Answer 24

reflect light back onto the retina to increase sensitivity of the eye in low light conditions

Question 28

in this case look at the positions of the left and right eye relative to the skull

what has happened to the right eye? what is it called?

Answer 28

right eye has been displaced out of the orbit –> exophthalmos