Special Senses Practical Flashcards
on the left side of the specimen identify the structures marked with coloured pins
green - rectus muscles
blue - lacrimal gland
what is the structure between the green pins
the optic nerve
is the 3rd eyelid the true eyelid
no
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
what is the shape of the cartilage that supports the 3rd eyelid
T
which muscle draws the eyeball caudally
retractor bulbi
which muscle does not originate in the area of the optic canal? where does it originate?
ventral oblique –> originates from the ventromedial orbital wall
what is the purpose of the trochlea for the dorsal oblique muscle
act as a pulley to change the direction of draw of the muscle
what is the presumed function of the oblique muscles
resist axial rotation of the eyeball during movement
what nerve(s) innervate the ocular muscles
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
on eyeball specimens identify
cornea, sclera, iris, ciliary body, ciliary processes, pupil, tapetum, optic nerve, limbus, anterior chamber, posterior chamber, vitreous chamber
what is the deviation of one eyeball called
strabismus
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
identify the structures of the ear on this MRI
what is abnormal in this scan
which is the diseased ear and why
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)
what is nystagmus
slow-quick flicking of the eyeball in association with rotating head movement –> also seen with diziness and disorders of the vestibular system
what is causing the problem
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
in the black head, identify the zygomatic salivary gland
what effect would enlargement of this gland (because of a tumour) have?
exophthalmos - the eyeball would be displaced out of the orbit and would be seen protruding on clincal examination
what is the function of the tapetum
reflect light back onto the retina to increase sensitivity of the eye in low light conditions
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?
right eye has been displaced out of the orbit –> exophthalmos
