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Opthalmology > Anatomy > Flashcards

Anatomy Flashcards

1
Q

where are most of the cones found?

A

in the fovea centralis of the macula

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2
Q

which nerve forms the optic disc?

A

CNII optic nerve

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3
Q

which bones make up the orbit?

A 
orbital plate of frontal bone
sphenoid bone (optic canal)
zygoma
lacrimal bone
nasal bone
orbital plate of ethmoid bone
maxilla (infra orbital canal and foramen)
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4
Q

what is the orbital rim?

A

superior, inferior, medial and lateral orbital margins which protect eye from trauma

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5
Q

structures of the eyelid?

A 
orbicularis occuli muscle
medial & lateral palpebral ligaments
orbital septum
superior and inferior tarsal plate
palpebral fissure
tendon of levator palpebrae superioris
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6
Q

what is the limbus?

A

corneo-scleral junction

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7
Q

what is the conjunctival fornix?

A

where sclera meets eyelid (conjunctiva is a defensive barrier covering the sclera and is a clear layer)

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8
Q

which cranial nerve stimulates the lacrimal gland to produce tears?

A

CNVII facial parasympathetic

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9
Q

what is the blood supply to the globe (eye)?

A

arteries from internal carotid:
posterior (& anterior?) cilliary arteries of uvea
opthalmic
central retinal

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10
Q

what is the venous drainage of the eye?

A

superior opthalmic vein drains into cavernous sinus
orbit drains anteriorly into facial vein
inferior opthalmic vein dreins into superior opthalmic vein
scleral venous sinus aka Canal of Schlemm
ciliary veins of uvea

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11
Q

name the main structures of the eye? CURL CAVS

A

Conjunctiva
Uvea (iris, cilliary body, choroid)
Retina
Lens

Cornea
Aqueous Humour
Vitreous
Sclera
(and occular adnexae: lids, lashes, lacrimal sac, naso-lacrimal duct)
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12
Q

what path do tears follow across the eye?

A

lacrimal gland superiorly (lateral canthus) –>
travel across cornea –>
superior & inferior lacrimal punctae; caruncle –>
medial canthus –> nasolacrimal duct –> lacrimal sac –> nose

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13
Q

which parts of the eye are avascular?

A

cornea and lens (nourished by aqueous)

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14
Q

what is the ‘blind spot’?

A

optic disc - where central retinal artery and vein and optic nerve enter the eye. it has no photoreceptors.

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15
Q

what happens if the central artery or vein of the retina is occluded and why?

A

complete interruption of flow in a retinal artery branch/”branch” retinal vein = loss of an area of visual field corresponding to the area of ischaemia
complete interruption of flow of the central artery (end artery) or vein = monocular blindness
this happens because they are end arteries which do not anastomose so occlusion –> ischaemia

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16
Q

what are the layers of the retina?

A

photoreceptors (posterior)
ganglion cells
axons of the ganglion cells (anterior)

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17
Q

list the occular muscles?

A

superior, medial, inferior & lateral rectus
superior & inferior oblique
levator palpebrae superioris

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18
Q

which muscle has a trochlea?

A

superior oblique

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19
Q

where do the rectus muscles originate from and where do they insert?

A 
origin = common tendinous ring attached to bones that make up the optic canal
insertion = sclera just posterior to cornea
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20
Q

what is the innervation of the extra-occular muscles?

A 
LR6 SO4 AO3
Lateral Rectus Abducens CN VI
Superior Oblique Trochlear CN iV
All others CN III Occulomotor
(remember CNII and CN VII also involved in the eye)
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21
Q

how does diplopia occur in orbital trauma?

A

fractured zygoma rotates medially into the floor of the orbit, damaging the suspensory ligament of the eye (attaches laterally to zygoma) lowers eye to orbital floor causing double vision

infraorbital neurovascular bundle can also be damaged, causing general sensory deficit to the facial skin

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22
Q

what is the general sensory nerve supply to the skin of the orbital region?

A

CN V facial:
V1 opthalmic - supraorbital branch, nasal skin and forehead skin branches (supplies upper eyelid, cornea, conjunctiva, nose)
V2 maxilliary - infraorbital nerve (supplies lower eyelid, skin over ala of nose and maxilla)
V3 mandibular (supplies skin over mandible and TMJ apart from angle of mandible which is C2,3)

23
Q

which nerves participate in the corneal (blink) reflex?

A

CN V trigeminal (sensory -afferent) long ciliary nerves form the first part of the afferent limb of the reflex and CN VII facial (motor - efferent)

24
Q

which neurotransmitters do sympathetic axons release in the pre and post synaptic neurones?

A 
presynaptic = acetyl choline
postsynaptic = noradrenaline
25
Q

what is the sympathetic chain/trunk?

A

presynaptic sympathetic axons from CNS exit at T1, ascend within sympathetic chain before synapsing in superior cervical sympathetic ganglion (superior, middle and inferior)

26
Q

what is the stellate ganglion?

A

inferior cervical and first thoracic ganglia fused together (they’re pals with Stella)

27
Q

what is the neurotransmitter released by parasympathetic nerves?

A

acetylcholine (both pre and post synaptic)

28
Q

where are ganglia located?

A

sympathetic - in the sympathetic trunk

parasympathetic - in the target organ

29
Q

how do presynaptic parasympathetic axons leave the CNS?

A

in CNs III, VII, IX, X plus sacral spinal nerves

30
Q

which nerve supplies the levator palpebrae superioris muscle?

A

AO3 - occulomotor CN III (forms ciliary ganglion)

note it contains skeletal and smooth muscle to open eyes wider

31
Q

how is pupil size controlled?

A

the ciliary nerves supply autonomic axons to control the diameter of the iris (& pupil) & the refractive shape of the lens

32
Q

what are the autonomic reflexes of the eye?

A

maximal eyelid elevation (symp)
pupilliary dilation (symp) /constriction (para) - pupillary light reflex
focusing the lens - accommodation reflex
lacrimation (para)
vestibulo-occular reflex - eye turns opposite way to head
oculocardiac reflex - reflex bradycardia due to extraoccular muscle tension or raised intraoccular pressure

33
Q

what is a mydriatic pupil?

A

non-physiologically enlarged pupil (mydriatic drugs can induce pupil dilation). Dilator pupillae fibres around the external circumference of the iris constrict and dilate pupil

34
Q

what is a pinpoint pupil?

A

often seen in opiate use; tiny pupil. contrast with blown (fixed dilated) pupil which can be serious pathology of CN III

35
Q

what is a miotic pupil?

A

as in Horner’s syndrome - non-physiologically constricted pupil

36
Q

what is the Edinger Westphal nucleus?

A

the location of the cell bodies of the parasympathetic axons of CN III, involved in pupilliary light reflex, located between the brain and optic tract

37
Q

what controls the refractive shape of the lens?

A

suspensory ligament of the lens,

cilliary muscles act like sphincters around cilliary body

38
Q

what is the accommodation reflex?

A

response to objects close to the eye. 3 components:

  1. bilateral pupilliary constriction (CN III)
  2. bilateral convergence - medial rotation of eyes (CN III)
  3. bilateral relaxation of the lens, becoming spherical (CN III)
39
Q

what are the 3 types of tears?

A

basal ( for cleaning; contain lysosyme)
reflex tears CN V1 and V2
emotional

40
Q

in which visual pathway does the nasal retina cross over at the chiasm?

A

RIGHT.
temporal visual field and nasal retina cross over
nasal visual field and temporal retina DO NOT cross over
anything from the right visual field is processed in left primary visual cortex.

41
Q

what are the causes of raised intracranial pressure?

A

increased pressure in CSF or in brain itself:
Brain tumour
Head injury
Hydrocephalus (increased fluid around the brain)
Meningitis
Stroke

42
Q

what visual problems occur with raised ICP?

A 
transient blurred vision
double vision
loss of vision
papilloedema (swelling of optic disc due to increased ICP)
pupillary changes
43
Q

what are the meninges?

A

dura, arachnoid, pia - layers that cover the brain

subarachnoid space is filled with CSF

44
Q

what is the dura mater?

A

splits into 2 layers; tough fibrous durable covering, sensory supply CNV, contains dural venous sinuses

45
Q

what is arachnoid mater?

A

looks spidery; arachnoid granulations - absorptive herniations - pathway for CSF

46
Q

what is in the subarachnoid space?

A

all blood vessels & CSF, continuously cushions and protects (between arachnoid and pia)

47
Q

what is pia mater?

A

faithful mother adheres to brain where arachnoid and dura don’t go into the sulci, pia does.

48
Q

where is CSF produced?

A

choroid plexus of the ventricles (3rd and lateral ventricles); reabsorbed into dural venous sinuses by arachnoid granulations

49
Q

at what spinal level should a lumbar puncture be performed?

A

L3/4 or L4/5 intervertebral disc levels to access subarachnoid space

50
Q

what are the ventricles of the brain?

A

left lateral
right lateral
3rd ventricle (midline with diencephalon)
4th ventricle (between cerebellum and pons)
3rd & 4th ventricle are connected by cerebral aqueduct; central canal of spinal cord is continuous with 4th ventricle

51
Q

how does raised intracranial pressure affect the eye?

A

Raised ICP will be transmitted along the subarachnoid space in the optic nerve sheath –> visual problems due to compression of optic nerve, central retinal artery & vein. Or bulging or swollen optic disc (papilloedema)

52
Q

what are the dural venous sinuses?

A 
superior sagital
inferior sagital
sinus rectus
confluens sinuum
cavernous sinus aka sphenoparietal
transverse
pars sigmoid
petros inferior
petros superior
53
Q

what are the folds of the dura mater?

A

septae falx cerebri (sickle shaped)

diaphragma sellae - tentorium cerebelli (tent over cerebellum). brain can herniate through openings e.g. tentorial notch

Opthalmology (4 decks)

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