Anatomy Flashcards
1
Q
What is the punctum?
A
the hole where the tears go down
2
Q
What does the conjunctiva cover?
A
- the sclera but not the cornea
- forms a valley called the conjunctival fornix
3
Q
What are the layers of the eye?
A
- Fibrous outer layer:
..Sclera- muscle attachment
..Cornea - Uvea vascular layer:
..Iris- pupil diameter
..Ciliary body- control iris, shape of lens and secretion of aqueous humour
..Choroid- this is highly vascular - Retina photosensitive inner layer:
..The posterior part is the visual part
4
Q
What is the limbus?
A
corneoscleral junction
5
Q
What are the eye segments?
A
- Anterior: this has an anterior chamber (between cornea and iris) and a posterior chamber (between iris and suspensory ligaments)
- Posterior: contains vitreous body with vitreous humour, floaters are here
6
Q
What is the iridocorneal angle?
A
the angle between the cornea and the iris
7
Q
What is the path of aqueous fluid?
A
- secreted by ciliary processes
- circulates and nourishes lens
- passes through pupils and nourishes cornea
- drains into the scleral venous sinus at the iridocroneal angle
8
Q
What is the arterial supply to the eye?
A
- ophthalmic artery is a branch of the internal carotid artery
- central artery of the retina runs within the optic nerve
- ciliary arteries supply the choroid layer
9
Q
What is the venous drainage from the eye?
A
- superior and inferior veins join and drain into the cavernous sinus
- some is also through the pterygoid plexus
10
Q
What are the features of the optic disc?
A
- where the optic nerve is formed
- point of entry for artery and blood vessels
- the blind spot
- is always on the nasal side
11
Q
What is the macula and the fovea?
A
the macula is where the greatest density of cones is and the fovea is at the centre of this
12
Q
What does light have to go through to get to the photoreceptors?
A
- retinal arteries and veins
- through ganglion cells
- through axons
13
Q
Where is light from objects in the lower visual field processed?
A
by the upper part of the primary visual cortex
14
Q
What are the planes and movements of the eye?
A
- Vertical (adduction or abduction)
- Transverse (elevation or depression)
- Anteroposterior axis (the superior pole of the eyeball goes laterally or medially- this is more of a rotation)
15
Q
What are the extra ocular muscles?
A
- superior rectus
- medial rectus (just primary movement)
- inferior rectus
- lateral rectus (just primary movement)
- superior oblique
- inferior oblique
- levator palpebrae (eyelid)
16
Q
How do you clinically test an extra ocular muscle?
A
- involves isolation of the muscles
- needs to line up with the angle of the pupil
17
Q
What is the movement of the lateral and medial rectus?
A
- Lateral rectus: this can only abduct the eyeball, CNVI, brings line of gaze into same plane as superior rectus and inferior rectus
- Medial rectus: can only adduct the eyeball, this brings the line of gaze into the same plane as the inferior and superior oblique
18
Q
What is the movement of the superior and inferior rectus?
A
- Superior rectus: when in abduction, SR can only elevate, CNIII
- Inferior rectus: when in abduction, IR can only depress , CNIII
19
Q
What are the movements of the superior and inferior obliques?
A
- Inferior oblique: when in adduction, this can only elevate, CNIII
- Superior oblique: when in adduction, this can only depress, CNIV
20
Q
What does pure elevation involve?
A
- superior rectus and inferior oblique
- elevates eyes synergistically
- antagonists as rotators
21
Q
What does pure depression involve?
A
- superior oblique and inferior rectus
- synergistically depresses
- antagonists as adductors/abductors
22
Q
What is the sensory innervation to the face?
A
- Ophthalmic: upper eyelid, cornea, conjunctiva, down to tip of nose
- Maxillary: skin of the lower lid, skin over the maxilla
- Mandibular: skin over mandible and TMJ, except angle of mandible
23
Q
What is involved in the blink reflex?
A
- somatic reflex
- CNV1 is sensory to cornea which then goes to the trigeminal ganglion this goes to CNV and then to the pons
- CNVII is the motor part of this reflex to the orbicularis oculi
- opening eye again is mainly levator palpebrae superioris
24
Q
What is the vestibulo-ocular reflex?
A
eyes automatically moving when the head moves
25
What is the oculocardiac reflex?
pressure on the eye, there is bradycardia to lower the BP
26
What is involved in the wide eye reflex in fight or flight?
- more light into eye and make pupil bigger
- focus on far away objects
- levator palpebrae superioris
- Mueller’s muscle (sympathetic of opening eyes wider than normal)
- fibres go to superior cervical ganglion, then internal carotid nerve, then plexus and the ophthalmic artery then branches
27
What is involved in constriction of the pupil?
- Parasympathetics constrict the pupils
- A miotic pupil is a non-physiologically constricted pupil eg Horner’s syndrome
- Sphincter pupillae fibres encircle pupil when it contracts
28
What is involved in the dilation of the pupil?
- Dilation is sympathetic innervation
- Mydriatic drug causes this
- Dilator pupillae fibres pull the sphincter apart to make the pupil wider
29
What is involves in the pupillary light reflex?
- afferent is ipsilateral CNII
- four neurone motor chain
- efferent is bilateral CNIII
- this is a consensual reflex
30
What is the accommodation reflex?
- actual lens
- spherical lens=near vision, parasympathetics, relaxed zonules, contract ciliary muscle, more reflective
- flat lens=far vision, no parasympathetics, ligament tightens
31
What happens when you bring your finger closer to your eyes?
- Bilateral pupillary constriction
- Bilateral convergence of both eyes towards midline
- Bilateral relaxation of the lens
- This is all CN3 oculomotor
32
What are the various lacrimation reflexes?
- Basal tears: all the time, lubricate and hydrate the eye, nourish the cornea
- Reflex tears: mechanical or chemical stimulation, afferent is CNV1, efferent is CNVII to the lacrimal gland which is via the pterygopalatine ganglion
- Emotional tears: parasympathetic innervation
33
How do the parasympathetic to the lacrimal gland work?
- branch of facial
- parasympathetic which is greater petrosal nerve
- rides on trigeminal
- to lacrimal gland
34
What is wrong if white sclera can be seen above the iris?
globes could be pushed forward eg in hyperthyroidism Graves’ disease
35
What are the main three symptoms of Horner's syndrome?
ptosis (droopy eyelid), only sweating on one side of the face and constricted pupil
36
What is Bell's palsy?
you can’t close your eyelid which is a CNVII palsy
37
What is included in uvea?
the iris, ciliary body and choroid so uveitis affects at least one of these
38
What happens in the brain with a light reflex?
the ipsilateral pretectal nucleus speaks to bilateral Edinger-Westphal nuclei so there is a consensual reflex
39
What is involved in the Relevant afferent pupillary defect?
- optic nerve problem on one side so the pupil constricts less than normal
- swinging light test
- shine in affected eye and both pupils will constrict
- quick shine in other eye and don't allow for dilation
- back to first eye and there will be an abnormal dilation in response to light (as the optic nerve is working less)
40
What is the explanation for upper and lower visual field loss?
- neurons in lower eye stay down in nerve etc
- upper bit goes straight back as it is not blocked by ventricle = parietal lobe
- lower bit is so comes front and round = temporal lobe
41
Where is the issue in a quadrantanopia?
in the optic radiations which are after the geniculate ganglia
42
What are the three orbital plates?
frontal, ethmoid, maxillary
| last two are very thin so can fracture
43
What goes through the superior orbital fissure?
CNs 3,4 and 6
44
What is the supraorbital notch and the infraorbital foramen for?
- supraorbital neurovascular bundle (CNV1)
| - infraorbital neurovascular bundle
45
What is a blow out fracture?
when the pressure or force is transferred and the thin bones at the back of the eye can fracture
fractures tend to be at sutures
46
Where do fractures in the eye tend to be?
fractures tend to be at sutures
47
What are the inner and outer parts of the superficial orbiculares oris?
```
inner = palpebral part
outer = orbital part
```
48
What is in the tarsi to stop tears overflowing?
glands to secrete lipids which line the eyelid to stop tears overflowing when they are produced normally
49
Where does the nasolacrimal duct empty?
into the inferior nasal meatus so when crying, the nose can run
50
What does the trochlea do?
causes the superior oblique muscle to change direction
51
Where do the rectus muscles all attach?
annulus ring
52
Where are the superior and inferior oblique muscles from?
Superior oblique is from sphenoid bone
| Inferior comes from orbital plate of maxillary bone
53
Where does the LPS muscle come from?
lesser wing of sphenoid bone
54
What is the innervation of the extra ocular muscles?
LR6 SO4 AO3
Lateral rectus is CN6
Superior oblique is CN4
All other extraocular muscles are CN3
55
What is the sympathetic supply to the eye?
- exits at T1
- moves up into the cervical region
- reaches the superior cervical ganglion
- synapses
- postsynaptic axons then exit by internal and external carotid nerves
- becomes a plexus around the internal carotid artery
56
What is the parasympathetic supply to the eye?
- leaves CNS by CN 3,7,9,10 or sacral nerves
- ciliary ganglion (parasympathetic and is just anterior to optic canal, related to CN3)
- only nerves that synapse in the ganglion are the parasympathetics from CN3
57
What is the path of CN3?
- comes off midbrain/pons junction
- passes through cavernous sinus
- enters cranial cavity at superior orbital fissure
- divides into superior and inferior division (related to the ciliary ganglion)
58
What are the meninges?
- protective coverings that surround the brain and the spinal cord
- they go through the foramen magnum
59
What are the layers of the meninges?
- Dura mater: hard covering, sensory nerve supply from CNV, has two layers which sometimes enclose the dural venous sinuses
- Arachnoid mater: this has a spider-like appearance
- Subarachnoid space: CSF and blood vessels are here
- Pia mater: adheres to the brain and follows its contours
60
Where can CSF be accessed form outside of the body?
L3/4 by a lumbar puncture without harming the spinal cord
61
Where does subarachnoid space reach down to?
S2 (spinal cord goes down to around L2)
62
What are the ventricles of the brain?
- right lateral
- left lateral ventricles
- midline 3rd ventricle
- 4th midline ventricle
63
What is involved in the circulation of CSF?
- Secreted by the choroid plexus in lateral ventricles and 3rd ventricle
- Passes in right and left lateral ventricle
- Then in the midline 3rd ventricle
- Via cerebral aqueduct
- To 4th ventricle into the subarachnoid space
- Reabsorbed via the arachnoid granulations which are outpouchings
- Into the dural venous sinuses
64
What is raised ICP caused by?
- chronic or acute
- caused by an increased pressure in fluid around the brain and within the brain eg tumour, stroke, head injury, hydrocephalus and meningitis
65
How does ICP increase?
the cranial cavity is closed off so if volume increases inside then pressure does too
66
Where does the brain matter shift in increased ICP?
towards foramen magnum and superior orbital fissure etc
67
What are the vision changes associated with increased ICP?
- transient blurred vision
- double vision
- loss of vision
- papilloemdema
- pupillary changes
68
What is special about the optic nerves?
they are actually CNS tracts so are covered by meninges (dura, arachnoid and pia)
69
How does raised ICP cause papilloedema?
the raised ICP is transmitted along the subarachnoid space to the optic nerve and central artery + vein of the retina
70
What are the symptoms of papiloedema?
- Transient visual obscurations
- Transient flickering
- Blurring of vision
- Constriction of the visual field
- Decreased colour perception
71
What can harm the oculomotor nerve?
- PCA ANEURYSM (emergency until proven otherwise)
- tumour
- microvascular
- MS
- congenital
72
What does damage to the oculomotor nerve cause?
- paralysis of the extraocular muscles (except SO+LR) including sphincter papillae and levator palpebrae superioris
- paralysis of parasympathetic innervation sphincter of the pupil
73
What is the clinical sign of oculomotor nerve damage?
- Down and Out (SO and LR working so right eye is down and out but left is straight)
- ptosis
- pupil dilation
74
What are the septa of the cranial cavity?
folds of dura create septa
- falx cerebri = sagittal plane
- tentorium cerebelli = with an opening called the tentorium notch and makes a tent over the cerebellum
brain can herniate through these openings
75
What is special about CNIV?
it has the longest intracranial nerve course of any cranial nerve
76
What does damage to the trochlear nerve result in?
- causes paralysis of the superior oblique muscle
| - can present as head tilt as the incyclo-torsion is weak
77
What is the clinical sign of CNIV damage?
- the eye will be superior when looking to the right as there is unopposed movement of the inferior oblique
- also diplopia when looking down
78
What can damage CNVI and what will this result in?
- causes are microvascular, raised ICP (bilateral as the brainstem is pushed down), tumour and congenital
- paralysis of lateral rectus muscle so there is medial deviation of the eye
79
What is special about CNVI?
the longest intradural course of all the CNs
80
Where do the nerves run in relation to the cavernous sinus?
- oculomotor and the trochlear run in the lateral wall in the dura
- abducens runs through the cavernous sinus itself
81
What are the symptoms of Horner's syndrome?
sympathetic aren't working
- droopy eye as Mueller’s isn’t working
- smaller pupil as the parasympathetics are unopposed
- less sweating and more vasodilation
82
What is the innervation of the cornea?
CNV1
83
What are the causes of CNIV nerve palsy?
- congenital
- microvascular
- tumour
- bilateral from a head trauma (the nerves stretch in whiplash trauma so they stop working)
84
How can you differentiate between a third nerve palsy due to aneurysm or microvascular issue?
- aneurysm presses on the outside of the nerve so the pupil will be dilated as this is where these parasympathetic fibres are
- microvascular will have a normal pupil as the problem won't affect these outside fibres
85
What happens with an inter-nuclear nerve problem?
- involves eye moving together
- caused by demyelinating lesion at the medial longitudinal fasiculus
- causes impaired adduction on the affected side and an abducting nystagmus on the other side
86
What is an supra-nuclear problem?
a problem with the inputs from higher centres in the brain which are telling the eyes to do something
87
What is the afferent and efferent for the blink reflex?
- afferent is 5 (nasociliary for corneal sensation)
| - efferent is 7 for motor
