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Ocular orbit and optic nerve visual pathways Flashcards

1
Q

What bones make up the roof of the orbit?

A

Lesser wing of sphenoid, orbital plate of frontal bone

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2
Q

What bones make up the lateral wall of the orbit?

A

Zygomatic process of frontal bone, greater wing of sphenoid, orbital surface of zygomatic bone

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3
Q

What bones make up the floor of the orbit?

A

Orbital process of palatine, orbital surface of maxillary bone, zygomatic bone

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4
Q

What bones make up the medial wall of the orbit?

A

Sphenoid body, orbital plate of ethmoid, frontal process of maxilla, lacrimal bone

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5
Q

What foramina of the orbit are there?

A

Optic canal, superior orbital fissure, inferior orbital fissure

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6
Q

What goes through the optic canal?

A

Optic nerve, ophthalmic artery

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7
Q

What goes through the superior orbital fissure?

A

Superior ophthalmic veins CNIII IV V1 VI

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8
Q

What goes through the inferior orbital fissure and what does it connect the orbit to?

A

Inferior ophthalmic vein, Infraorbital nerve and vessels, zygomatic nerve from pterygopalatine ganglion
Connects the orbit with the pterygopalatine fossa

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9
Q

What is the most and second most common walls of the orbit to be fractures?

A

Medial wall is the thinnest and most commonly fractured since there are many small bones joined in one area.
Floor is second most commonly fractured part since the maxilla is mostly hollowed by the maxillary sinus

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10
Q

What happens in an orbital floor blow out fracture?

A

Hard object hitting the orbit will carry the pressure backwards, fracturing the medial wall or floor. If the floor fractures, contents of the orbit can go into the maxillary sinus, creating inflammation as well as restriction in the functions of the eyeball, so movement of eyeball affected. Infraorbital nerve will be damaged.

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11
Q

Orbital contents

A

Eyeball, lacrimal gland, extraocular muscles, ciliary ganglion, nerves, arteries, veins, fascia

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12
Q

What arteries are part of the orbits contents?

A

Ophthalmic, central retinal, ciliary arteries

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13
Q

What veins are part of the orbits contents?

A

Superior and inferior ophthalmic veins, central retinal vein

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14
Q

What does the orbit fascia attach?

A

Periorbita attached to the periosteum of orbital bones. Attaches the eyeball in the form of suspensory ligaments. It is continuous with the dura at the superior orbital fissure and optic canal. At the orbital margin it makes orbital septum of the eyelids.

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15
Q

What is the common tendinous ring?

A

A thick ring that gives origin to the 4 rectus muscles.

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16
Q

What holds the superior oblique tendon in position?

A

Trochlear

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17
Q

What does the orbital fascia split to enclose?

A

Lacrimal gland, sac and nasolacrimal canal

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18
Q

What are the eyelids made of?

A

Skin - keratinatsed stratified squamous epithelium, subcutaneous tissue, muscles, fascia, conjunctiva

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19
Q

What is the tarsal plate of the eyelid?

A

Fascial condensation rich in sebaceous glands

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20
Q

What muscles are in the eyelid?

A

Orbicularis oculi - facial nerve innervates to close the eye
Levator palpebrae superioris - Oculomotor nerve to open the eye
Muller (superior tarsal muscle) - sympathetic nerve supply to open the eye

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21
Q

What is conjunctiva of the eye?

A

Mucous membrane covering the palpebral part of the eye

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22
Q

What artery supples the medial aspect of the orbit?

A

Facial artery (branch of ECA)

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23
Q

What supplies blood to the lower eyelid?

A

Maxillary artery travels in the floor in the form of the of Infraorbital artery

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24
Q

What is the main blood supply to the eye?

A

Ophthalmic artery (branch of ICA) - supplies eyeball, lacrimal gland and extraocular muscles

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25
What supplies the retina?
Branch of the ophthalmic artery - central retinal artery - goes within optic nerve to supply the retina. End artery = only blood supply to the retina.
26
How does the orbit drain anteriorly?
On medial side it drains away via the facial vein which opens into internal jugular vein. So orbit anteriorly drains into the IJV.
27
How does the orbit drain posteriorly?
Posteriorly the superior ophthalmic vein drains into the cavernous sinus.
28
What happens if inflammation of the eye is carried back into the brain?
Leads to cavernous sinus thrombosis
29
What does the inferior ophthalmic vein open into?
Pterygoid venous plexus
30
Lymphatic drainage of the eye
From the lateral side it drains into the parotid/pre-auricular node From the medial side it drains into the submandibular and submental nodes
31
What is the lacrimal gland responsible for?
Reflex tearing - e.g., from sneezing, coughing wind etc
32
What is baseline tearing provided by?
Conjunctival goblet cells and glands
33
How do tears work when crying?
Ductules open into upper fornix. Lacrimal canaliculi via lacrimal punctual lacrimal sac. Then drips down via the nasolacrimal duct which opens into the inferior meatus of the nose (thus we get a snotty nose when crying)
34
Where is the lacrimal gland and lacrimal sac located?
Lacrimal gland is in the superolateral aspect of the orbit Lacrimal sac is in the lacrimal groove (anteromedial)
35
Afferent path for the parasympathetic secretomotor reflex to tearing
Sensation carried to lacrimatory nucleus of facial nerve. This sends impulses through the nervus intermedius to the greater petrosal nerve. This joins the deep petrosal nerve to form the vidian nerve, which goes into the pterygopalatine fossa and synapses in the pterygopalatine ganglion. These parasympathetic fibres hitchhike on the maxillary nerve, zygomatic nerve (CNV2) and lacrimal nerve (CNV1).
36
What is the main nerve for corneal sensation?
Trigeminal nerve (sensory). Also provide support for parasympathetic stimulation to go along.
37
Where do the recti muscles originate and insert?
Originate from the common tendinous ring and insert into the sclera
38
Where do the superior oblique and levator palpebrae superior originate?
Body of sphenoid (above optic canal)
39
Where does inferior oblique originate?
Orbital floor medially
40
Where is the anterior chamber of the eye and what is it filled with?
Between cornea and iris and filled with fluid - aqueous humour
41
Where is aqueous humour secreted?
By the epithelium of the ciliary processes of the ciliary body.
42
What is the vitreous body full of?
Gelatine
43
Describe the outer layer - sclera
Opaque. Made of type I collagen fibres. Maintains shape and pressure. Protects eye from infection and trauma. Perforated by muscles, nerves and vessels. Continues with the dura sheath (dura covering the optic nerve)
44
What is the cornea made from?
Type I collagen fibres
45
How is the cornea transparent?
Avascular Special arrangement of equisized collagen fibres Dehydrated - maintains by Descement’s membrane and endothelium by Bowman’s layer
46
Function of cornea
Refracts incoming light Protective barrier to infection and trauma
47
How is the pupil controlled?
Anterior layer of the iris: dilated by sphincter muscles by CNIII, narrows by dilator pupillae muscle supplied by sympathetic nerves
48
What does the choroid do?
Carries blood vessels and supplies blood to retinal outer layers
49
What is phototransduction?
Conversion of light energy into impusles
50
What cells are in the retina?
Retinal ganglion cells, bipolar, cones/rods (direct pathway) Amacrine, horizontal (indirect pathway)
51
What is the optic disc?
Blind spot - has no cones or rods. Optic nerve head.
52
What is the macula?
Where most of the rods and cones are located
53
What is the fovea?
Centre of the macula and is rod free and has highest visual acuity. Contains only cones.
54
Why is the optic nerve part of the CNS?
It is enveloped by the 3 meningeal layers. Exits the eyeball at posterior sclera foramen and is myelinated by oligodendrocytes.
55
Where does the optic nerve terminate?
Optic chiasm
56
How do the optic nerve fibres cross in the chiasm?
All fibres come out from the retina through the optic nerve. But fibres from the nasal side cross in the chiasm to the opposite side.
57
What can happen in pituitary adenoma?
It will compress the optic chiasma, affecting the cross fibres
58
Relations of the optic chiasma.
Anteriorly: ACommA Posteriorly: PC Superiorly: hypothalamus Laterally: ICA Inferiorly: pituitary gland, sphenoid sinus and cavernous sinus
59
What is the optic tract?
Extends from the optic chiasma to the lateral geniculate nucleus (thalamus). Contains crossed and uncrossed fibres.
60
What happens in damage to the optic nerve is damaged?
There will be visual field loss in one eye
61
What happens if the optic chiasm is damaged?
There will be both visual fields lost in the opposite direction.
62
What happens if the optic tract is damaged?
Site of vision is lost
63
Afferent component of the pupil light reflex
Optic nerve stimulated by light. Some of it crosses in the chiasma, which is why when one pupil is stimulated, both will contract.
64
Where is the reflex centre for the pupil light reflex?
Pretectal nuclei Edinger Westphal nuclei.
65
Efferent response to the pupil light reflex
Oculomotor nerve to sphincter pupillae
66
Difference between direct and indirect pupil reflex
Direct is when the pupil is directly stimulated. Indirect is when you stimulate one pupil but the other pupil constricts.
67
If the right optic nerve is not working, what do you test?
Must check the other non blind eye to test whether the oculomotor nerve is working via constriction of the pupil.
68
What is the visual pathway?
Visual sensations will end in the thalamus and then go to the visual cortex. Will not affect pupil reflex if blind due to visual cortex damage.
69
Where is the visual cortex?
In the occipital lobe
70
What is the accommodation reflex?
If an object is closer, the light rays entering the eye are more divergent, requiring more refraction for focusing so more converging power from the lens. This is the function of the accommodation reflex. Ciliary muscles must contract to release zonular pressure and make the lens more convex so it can focus on objects nearby onto the retina.

CFB (34 decks)

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