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anatomy - head,neck,spine > orbit > Flashcards

orbit Flashcards

1
Q

what are the bones of the orbit *

A

roof - orbital plate of the frontal bone

floor - orbital plate of the maxilla (thin) (cheek bone)

lateral wall - zygoma and greater wing of sphenoid (posterior to the zygoma)

medial wall - frontal process of maxilla, lacrimal bone (small), orbital plate of ethmoid (lamina papyracea), lesser wing of sphenoid

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2
Q

what is a blowout injury

A

when there is driect trauma to the eye

blow put floor of orbit

eye drops into cheek cavity = double vision etc

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3
Q

what are the orbital formina *

A

optic canal - optic nerve (CN2), opthalamic artery

inferior orbital fissure - maxillary division of trigeminal V2, infraorbital vessels

superior orbital fissure - CN involved in extrinxic muscle function (CN3 4 6), opthalmic division of trigeminal V1, opthalmic vessels, sympathetic fibres run with vessels

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4
Q

what is the opthamlic artery *

A

the main blood supply to the eye

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5
Q

where are the orbital foramina *

A

optic canal - in the lesser wing of the spenoid bone

superior orbital fissure - in lesser wing of sphenoid

inferior orbital fissure - lesser wing of the sphenoid (nerves run along maxilla and exit via the infraorbital fissure)

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6
Q

what are the 2 categories of the extrinsic muscles of the orbit *

A

recti

obliques

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7
Q

describe the recti muscles *

A

inferior, superior, medial and lateral

origin - at back of orbit in common tendinous ring

insertion - into the sclera, 5mm behind the corneal margin (anterior to the equator)

nerve supply - inferior superior and medial are innervated by oculomotor CN3, lateral abducens CN6

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8
Q

describe the oblique muscles (extrinsic muscles of the orbit) *

A

inferior and superior

origin - inferior: in orbital surface of maxilla

Superior: from the body of the sphenoid

insertion - inferior: into the posterior/inferior quadrant of thee globe

superior: posterior/superior quadrant via the trochlea (bony spur in medial aspect of orbit)

nerve supply - inferior: CN3, superior: trochear nerve CN4

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9
Q

what is the muscle of the upper eyelid *

A

levator palpebrae superioris

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10
Q

describe the levator palpebrae superioris *

A

origen - lesser wing of sphenoid

insertion - into the superior tarsal plate and skin of the eyelid

nerve supply - CN3, and sympathetic supply to sm (important clincially)

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11
Q

why is it important clinically that the levator palpebrae superioris has sympathetic innervation *

A

horner’s syndrome (loss os SNS to head and neck)

symptom is ptosis (drooping of upper eyelid)

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12
Q

describe the path of the optic nerve and its insertion into the globe *

A

through the optic canal to the back of the globe

large nerve

retinal ganglion cells axons going back via optic chiasm to the occipital lobe

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13
Q

what is the common tendinous ring, where is it *

A

origin for all the muscles in the orbit

back of the orbit

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14
Q

describe the muscles and their location in the orbit *

A

levator palpebrae superioris - at the top of orbit, muscle to the upper eyelid

superior oblique - origin in c tendinous ring, up passes through pully system with trochlear, pass back to lateral superior quadrant of the globe, inserts into the posterior globe of the eye

superior rectus muscle - origin in common tendinous ring at back of orbit - insert into globe of eye anterior to equator

inferior oblique - originates in orbital plate of the maxilla (in the lower orbital nasal wall), inserts into the posterior globe of the eye

inferior rectus - origin in common tendinous ring at back of orbit - insert into globe of eye anterior to equator

lateral rectus - origin in common tendinous ring at back of orbit - insert into globe of eye anterior to equator

medial rectus - origin in common tendinous ring at back of orbit - insert into globe of eye anterior to equator

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15
Q

describe the function of the superior oblique muscle *

A

contraction = move pupil down and out

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16
Q

function of the superior rectus *

A

straight forward contraction pulls pupil up

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17
Q

describe the function of the inferior oblique muscle *

A

moves the pupil up and ou t

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18
Q

describe the function of the inferior rectus *

A

depresser muscle - move pupil down

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19
Q

describe the function of the lateral rectus *

A

abduct the eye - pull the pupil away from the midline

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20
Q

describe the function of the medial rectus *

A

adduct the eye - move pupil to the middle

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21
Q

describe ISOLATED muscle actions - ie not what would happen in real life *

A

LR - abduction

MR - adduction

SO - depressor and abductor

IO - elevator and abductor

SR - adduction and elevation

IR - adduction and depression

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22
Q

describe how you test the muscle action of the orbit clinically *

A

you need to get eye so that it is line with the muscle that you are testing

LR and MR - see whether eye follows finger - adduction/abduction (remember 1 eye will adduct and one will abduct in persuit so different muscles are being used in each eye)

to check depression - adduct/abduct first so you can isolate the muscle that is causing the depression. when adducted - SO, abducter - IR

elevation - also need to adduct/abduct first - adduct - IO, abducted - SR

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23
Q

what are the nerves of the orbit superficially

A

optic - made of axons of ganglion cells in retina

oculomotor - has 2 rami, motor fibres to MR, SR, IF, IO, LPS (eyelid), PNS fibres

trochear - motor to SO

abducens - motor fibres to LR

24
Q

what are the branches of the opthalmic division of the trigeminal nerve

A

lacrimal

frontal branches into supratrochlear and supraorbital,

nasocilary branches to ciliary ganglion PNS, ethmoidal and infratrochlear

25
Q

describe the location of the nerves of the orbit and how they reach the orbit

A

oculomotor goes through superorbital fissure

trigeminal ganglion sits in Meckel’s cave, opthalmic division enters orbit through superorbital fisure

branches of the opthalmic division of the trigeminal nerve - frontal nerve, lacrimal nerve (going to lacrimal gland on lateral orbit)

26
Q

describe the location of the CN in the cavernous sinus and relevance of this

A

in the lateral wall

except abducens CN6, runs with the internal carotid

infection/thhrombosis here can affect all these nerves

27
Q

describe the ciliary ganglion

A

PNS innervation

sits behind globe of eye

preganglionic fibres are in the inferior ramus of oculomotor nerve

postganglionic fibres are in the short ciliary nerves

they innervate the sphincter pupillae and ciliary muscle

28
Q

describe the blood vessels of the orbit

A

opthalmic artery supplies blood to central artery of retina, muscular branches, ciliary, lacrimal, supratrochlear and supraorbital branches

opthalmic veins - superior (drain into cavernous sinus - potential route of infection back into cranial cavity) inferior (drain into the pterycoid plexus - no passage into the cranial cavity)

29
Q

why is it important to look at arteries in eye clinically

A

check that they are ok

also check systemic disease

in diabetics - can see diabetic retinopathies

in people with trauma see papilloedema indicate raised intracranial pressure

30
Q

summarise the lacrimal system

A

lacrimal gland in the anterolateral superior orbit

PNS secretomotor fibres are from facial nerve CN 7 - they come from the pterygopalatine ganglion, pass through zygomaticotemporal branch and then join lacrimal nerves. (ganglion is behind the cheek) lacrimal nerves are sensory branches of trigeminal

lacrimal sac in medial canthus of eye - drains into inferior meatus of the nose via the nasolacrimal duct

31
Q

describe tears

A

they wash across the cornea

have a protective function

keep eye moist

collect in lacrimal sac and drain through nasolacrimal duct into nose

32
Q

what could be the problem if someone presents with a dry eye

A

a PNS problem - no production of tears

33
Q

what are the afferent and efferent arms of the corneal reflex *

A

afferent - CN5

efferent - CN7

34
Q

what are the afferent and efferent arms of the pupillary light reflex *

A

afferent - CN2

efferent - CN 3

35
Q

What are the afferenet and efferent nerves of the accommodation reflex *

A

Afferent CN2

efferent CN 3

36
Q

Describe the optic nerve *

A

Extension of brain from retina to visual centers of the brain

leaves the orbit through the optic canal

37
Q

Describe the oculomotor nerve *

A

Leaves the brain stem between meidbrain and pons

passes through the cavernous sinus

branches into superior and inferior divisions just before orbit

they enter the orbit through superior orbital fissure lying in the common tendinous ring

superior branches passes up over CN2 innervatibg the superior recurs an elevator palpebrae superioris

inferior branch has 3 branches innervatibg medial, inferior rectud and inferior oblique

3rd branch of inferior gives rise to the ciliary ganglion - this is the pns root to ganglion

38
Q

What is the edinger Westphalia nucleus *

A

The pns pregnaglionic nucleus - pns outflow to the ciliary ganglion

39
Q

Describe the pretectum *

A

Group of 7 nuclei

most known function is the pupillary light reflex controlled by the olivary pretectal nucleus

40
Q

What is horners syndrome *

A

Loss of sons function in head

because of a lesion

41
Q

What are the 3 typical features of horners syndrome *

A

Pupillary constriction because of paralysis of the dilator pupillary muscle

partial ptosis- dropping of upper eyelid due to paralysis of superior tarsal muscle

absence of sweating on the ipsilateral side of face and neck due to absence of innervatibg of the sweat glands,

42
Q

Describe the tarsal muscle *

A

Superior tarsus in upper eyelid - part of the levator palpebrae superioris

inferior in lower eyelid

they are plates of dense connective tissue

43
Q

Describe the path of the sympathetic fibers of the orbit *

A

Arise from t1

enter sympathetic chain through the white rami communicants - ascend to superior cervical ganglion - synapse with post ganglion fibers

post gang fibres travel with internal carotid artery and branches (ophthalmic artery)

then either go through the ciliary ganglion and join with short ciliary nerves, or pass through long ciliary nerves - both reach eye

innervate the dilator pupillary muscle

44
Q

Describe the superior cervical ganglion *

A

Area of c1-2

45
Q

What is the effect of loss of CN3

A

Complete ptosis - loss of supply to legatos palpebrae superiosis

46
Q

describe the action of the ciliary muscle *

A

it is controlled by parasympathetics from the oculomotor nerve

contraction of the ciliary muscle decreases the size of the ring formed from the ciliary body - reducing tension on the suspensory ligament of the lens

therefore the lens is more relaxed so rounded causing accomodation for near vision

that is why eyes get tired looking at near objects becasue of contraction of the ciliary muscle

47
Q

describe the action of the sphincter pupillae *

A

muscle fibres in the iris

innervated by parasympathetics from oculomotor nerve

when contract they constrict pupil

48
Q

describe the action of the dilator pupillae *

A

fibres in the iris

innervated by sympathetics from the superior cervical ganglion T1

contraction dilates the pupil

49
Q

how do you test if someone has a squint*

A

shine light 40cm away from eye straight on

the light should be reflected symaettrically from the cornea on both eyes - if unsymetrical - show have a squint which is ocular misalignment - used to test the muscle function of the eye

when pt looks at light, reflection should be nasal to the centre of both pupils

50
Q

describe opthalamoscopy

A

you vcan see the vitreous chamber of the eye using an opthalmoscope - small battery operated light with tiny lens so yoiu can see the vitreous chamber and the posterior wall of the eye

you can see the optic nerve, the typical 4 branches of the central retinal artery and the fovea

shine the light in the eye and look for the red reflex - then get closer until you can see the arteries of the eye

51
Q

describe 6th nerve palsy *

A

affect to lateral rectus muscle

unable to abduct so eye deviates in

souble vision bad when looking to side of effected eye because eye cant move in that direction

52
Q

describe 4th nerve palsy *

A

superior oblique muscle is affected

eye looks medial and is raised

53
Q

describe the conjunctiva *

A

it is a thin membrane covering the posterior surface of the eyelid

it covers the full extent of teh posterior surface of the eyelid and reflects onto the sclera

it attaches to the membrane at the junction between the sclera and conjunctiva

a conjuctival sac is formed when eyes are closed and upper and lower extensions of these sacs are the superior and inferior conjunctival fornices

54
Q

importance of the conjunctiva *

A

keep the eye and inside surface of eyelid lubricated and moist so eye can open without friction which would cause eye irritation

55
Q

describe the eyelid anatomy *

A

space between eyelids when open is the palpebral fissure

the layers of the eyelids are; skin, subcutaneous tissue, vol muscle, orbital septum, tarsus, conjunctiva

the superior eyelid has 2 more muscles than the lower eyelid

56
Q

describe the innervation of eyelid *

A

sensory is from trigeminal branches - opthalmic and maxillary nerve

motor is from - facial, oculomotor and sympathetic fibres

57
Q

function of the eyelid *

A

spread tears across the eye

protect the eye from foreign bodies

anatomy - head,neck,spine (7 decks)

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