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Ophthalmology > Anatomy > Flashcards

Anatomy Flashcards

1
Q

Which bones make up the orbital rim?

A

Maxilla
Zygomatic
Frontal

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2
Q

Apart from the bony orbit, what other structures protect the eyeball?

A

Eyelids
Eyelashes
Lacrimal glands + ducts
Conjunctiva

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3
Q

What is the name of the slightly thickened are of connective tissue which contains glands, and sits on the inside of the eyelid?

A

Tarsal plate

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4
Q

Which nerve supplies orbicularis oculi?

A

CN VII - facial

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5
Q

Which three nerves supply the skeletal muscles of the eye?

A

CN III - oculomotor
IV - trochlear
VI - abducens

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6
Q

Which muscle works to elevate the eyelid?

Which nerve supplies this muscle?

A

Levator palpebrae superioris

CN III - oculomotor

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7
Q

Give two functions of tears

A

Keeps eyes moist, helps to supply the cornea with oxygen

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8
Q

Describe the pathway of tears starting from lacrimal gland

A

Lacrimal gland

  • > across cornea
  • > puncta lacrimalia
  • > canaliculi
  • > lacrimal sac
  • > nasolacrimal duct
  • > into nose through inferior meatus of lateral wall of nasal cavity
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9
Q

Which nerve innervates the lacrimal gland?

A

CN VII - facial

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10
Q

Which cranial nerves have a parasympathetic component?

A

CN III - oculomotor
CN VII - facial
CN IX - glossopharyngeal
CN X - vagus

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11
Q

Why can the trigeminal nerve not supply the lacrimal gland?

A

Trigeminal has no parasympathetic component so cannot supply a gland

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12
Q

What are the two broad types of conjunctivitis?

How do they present?

A

Bacterial - tends to present with pus

Allergic - tends to present with erythema

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13
Q

What are the three layers of the eye ball and which structures do each contain?

A 
Outer fibrous:
- Sclera 
- Cornea
Middle vascular 
- Pigmented
choroid 
- Ciliary body 
- Iris
Inner nervous
- Retina
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14
Q

What is the ciliary body made up of?

How does the lens move if the muscles are relaxed/tensed?

A

Ciliary muscles + suspensory ligament of lens
When the muscles relax, the ligaments are pulled and put tension on the lens to thin it
When the muscles contract they relax the suspensory ligaments, allowing the lens to become fatter

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15
Q

Which type of muscle is found in the iris?
What are the two muscles?
- Nervous innervation?
- Under what circumstances do they move?

A

Ssmooth muscle fibres

  1. Sphincter (constrictor) pupillae (concentric)
    - Parasympathetic control from CN III
    - Bright light, accommodation
  2. Dilator pupillae (radial)
    - Sympathetic
    - Dim light, fright
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16
Q

Name each of the extrinsic muscles of the eye and the direction in which they move the eye

A 
Superior rectus - elevates and adducts
Inferior rectus - depresses and adducts
Lateral rectus - abducts
Medial rectus - adducts
Inferior oblique - up and out
Superior oblique - down and out
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17
Q

Which nerves supply the extrinsic muscles of the eye?

A

All are supplied by CN III except:

  • Lateral rectus which is supplied by CN VI (abducens)
  • Superior oblique which is supplied by CN IV (trochlear)
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18
Q

Give some features of the superior oblique muscle

A
  • Passes through the trochlea
  • Attaches to sclera
  • Supplied by trochlear nerve
  • Tramp muscle – down and out
  • Makes the eyeball go down and out
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19
Q

Revise testing of the eye muscles

A

Revise testing of the eye muscles

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20
Q

What is the suspensory ligament of the eye?

A

A thick fascial sling that holds the eye just above the floor of the orbit

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21
Q

What can happen to the suspensory ligament if the zygoma is #?

A

If trauma occurs to the cheek and the zygoma is #, the zygoma rotates medially in towards the floor of the orbit – suspensory ligament will be displaced and move inferiorly – eye will also descend within the orbit
Double vision results as eyes are in different orientations

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22
Q

What runs along the floor of the orbit?

What can displacement of the zygoma do to this?

A

Running along floor of orbit is the infraorbital canal/groove
- Contains NV bundle – nerve, artery, vein
- Infraorbital nerve, artery and vein
Displacement of zygoma can impinge upon this canal and cause damage to the NVB – can result in sensory loss to the mid face region

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23
Q

In terms of general sensory supply to the face, what areas do the branches of the trigeminal nerve supply?
Which nerve supplies the angle of the mandible?

A

CN V1 (ophthalmic nerve) supplies:
- Upper eyelid
- Cornea
- All the conjunctiva
- Skin of the root/bridge/tip of the nose
CN V2 (maxillary nerve) supplies: - Skin of the lower eyelid
- Skin over the maxilla
- Skin of the ala of the nose
- Skin/mucosa of the upper lip
CN V3 (mandibular nerve) supplies: - Skin over the mandible and temporomandibular joint (apart from the angle of the mandible – supplied by C2,3 spinal nerves)

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24
Q

Which reflex prevents damage from foreign bodies striking the anterior surface of the eye?
How does it work?

A 
The blink (corneal) reflex
APs travels centrally along divisions of CN V1 from the cornea to the trigeminal ganglion, then in CN V to the pons
APs are conducted peripherally in CN VII to the                             eyelid part of orbicularis oculi
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25
Q

What are the functions of the two parts of orbicularis oculi?

A

Palpebral part allows us to close our eyes gently i.e. blink
Orbital muscles cause us to scrunch up our eyes

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26
Q

How do sympathetic axons course from the CNS to the organs of the head region?

A

The presynaptic axon extends from CNS to synapse with a ganglion – associated with the sympathetic chain in the sympathetic nervous system
AC is the neurotransmitter here

Postsynaptic axon extends from the ganglion towards the organ
Noradrenaline is the neurotransmitter here
The effect is smooth muscle contraction or glandular secretion?

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27
Q

How do sympathetic axons course from the CNS to the eye?

A

Presynaptic axons descend through the spinal cord and exit in the T1 spinal nerve, then ascend within the cervical chain
They then synapse in the superior cervical sympathetic ganglion, then fibres either travel in the internal or external carotid nerve – both contain synaptic sympathetic axons
The fibres then pass onto a plexus which is an intertwining of nerves – found near the internal or external carotid artery depending on which nerve we’re talking about
The plexus associated with the internal carotid artery – ophthalmic artery – sympathetic axons are carried by the artery to the eye

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28
Q

Which cranial nerves carry parasympathetic axons?

A

CN III - oculomotor
CN VII - facial
CN IX - glossopharyngeal
CN X - vagus

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29
Q

How do parasympathetic axons course from the CNS to the organs of the head region?

A

Presynaptic axon leaves the CNS in CN III, VII, IX or X
The presynaptic axon releases acetylcholine at the synapse in the parasympathetic ganglion to stimulate the cell body of the postsynaptic axon
The postsynaptic axon releases acetylcholine at the organ to stimulate the organ to respond (smooth muscle contraction or glandular secretion)

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30
Q

What is the main difference between sympathetic and parasympathetic nervous systems?

A

The positioning of the ganglia – in parasympathetic NS the ganglia tend to be isolated within the head and neck, or associated with the surfaces of the organs themselves

31
Q

How do parasympathetic presynaptic axons leave the CNS?

A

All presynaptic parasympathetic axons leave the CNS in

  • Cranial nerves III, VII, IX & X
  • Plus sacral spinal nerves - “carry” parasympathetic axons to the hindgut, pelvis & perineum
32
Q

How many parasympathetic ganglions are in the head?

A

Four

33
Q

Which parasympathetic ganlgion is associated with the eye?

A

Ciliary ganglion in the orbit

34
Q

How many ganglia are associated with the facial nerve?

A

Two

35
Q

What is the fourth parasympathetic ganglion in the head?

A

Otic ganglion – associated with CN IX – to parotid for secretion of saliva

36
Q

What is the function of the vagus nerves?

A

The vagus nerves supply parasympathetic axons to the organs of the neck/chest & abdomen as far as the midgut

37
Q

Give three functions of the oculomotor nerve

A
  1. (somatic) motor to superior (SR), medial (MR) & inferior rectus (IR) and inferior oblique (IO)
  2. (somatic) motor to levator palpebrae superioris (LPS)
  3. Presynaptic parasympathetic axons to the ciliary ganglion
38
Q

Describe the path of the oculomotor nerves to the orbit from the CNS

A

Connects with brain at junction between midbrain and pons

After leaving the brain it leaves the cranial cavity via superior orbital fissure - enters the orbit

39
Q

What are the two branches of the oculomotor nerve?

What are the functions of the two parts?

A

Superior and inferior

  • Superior supplies superior rectus and LPS
  • Inferior branch supplies medial rectus, inferior rectus and inferior oblique – motor
  • Inferior also conveys presynaptic parasypmpathetics to the ciliar ganglion
  • Superior is ONLY MOTOR
  • Inferior is motor and presynaptic parasympathetic
40
Q

Which four structures pass through the superior orbital fissure?

A

CN III - oculomotor
CN IV - trochlear
CN VI - abducens
CN V1

41
Q

What are the two types of ciliary nerve?

What are the components of each?

A 
Long ciliary nerve
- Sympathetic
- Somatic sensory
Short ciliary nerve
- Somatic sensory
- Parasympathetic
- Sensory
42
Q

Which fibres pass through the ciliary ganglion?

A
  • General sensory fibres from the cornea and conjunctiva
  • Post synaptic sympathetic fibres from the superior cervical ganglion (don’t synapse here, just pass through)
  • Presynaptic parasympathetic fibres from CN III, which synapse with:
  • Postsynaptic parasypathetic fibres
43
Q

Which nerves does the vestibulo-ocular reflex require?

A

CN VIII & CNs III, IV & VI

44
Q

What is the oculocardiac reflex?

Which nerves are required for it?

A
  • Reflex bradycardia in response to tension on the extraocular muscles or pressure on the eye
  • CNS connections between CN V1 & CN X
45
Q

Give three effects the sympathetic NS has in the eye

A
  • Open eyes wider to let more light in
  • Focus on far objects
  • Emotional lacrimation
46
Q

Give four effects the parasympathetic NS has in the eye

A
  • Allow orbicularis oculi to work
  • Get less light into eyes (to protect the retina from bright light or when asleep)
  • Focus on near objects
  • Reflex lacrimation (to wash away the stimulant foreign body & clean the cornea)
47
Q

What type of muscle does the LPS contain?

What is the function?

A

SKELETAL
- Voluntary from oculomotor
SMOOTH
- Sympathetic - not voluntary

48
Q

What do sympathetics do to the pupil?

Which muscle?

A

Ssympathetics dilate the pupil
Dilator pupillae muscle is responsible for this – arranged radially around the pupil
Has a fixed origin around the external surface of the iris
Mobile insertion is around the internal bit of the iris

49
Q

Which muscle constricts the pupil?

Which NS?

A

Sphincter/contrictor pupillae

Parasympathetic

50
Q

What is a fixed pin point pupil associated with?

A

Opiate drugs

51
Q

What is a fixed dilated pupil associated with?

A

Serious pathological sign of oculomotor nerve dysfunction

inhibiting the pupillary constricting action of parasympathetic axons in the ciliary nerves

52
Q

Which eye is the stimulated eye and which is the non-stimulated eye?

A

The eye with the light being shone = directed light reflex

Other eye = consensual light reflex

53
Q

What is the pathway of APs when light is shone in the eye?

A
  • The (special) sensory (afferent) limb of the reflex is the ipsilateral CN II (the optic nerve)
  • CNS connections in the thalamus
  • The motor limb of the reflex is bilateral via CNs III (the oculomotor nerves)
54
Q

Describe the events that take place related to the lens when looking at a distant object

A

The ciliary muscle relaxes in “far vision” (no parasympathetics) the ligament tightens & the lens flattens to focus on distant objects

55
Q

Describe the events that take place related to the lens when looking at a near object

A

the ciliary muscle contracts in “near vision” (parasympathetic) the ligament relaxes & the lens becomes spherical to focus on close objects

56
Q

What are the three components of the accommodation reflex which need to be assessed?

A
  1. Bilateral pupillary constriction (CNs III)
    to prevent diverging light rays from hitting the periphery of the retina and resulting in a blurred image.
  2. Bilateral convergence - medial rotation of both eyes (CNs III)
    simultaneous movement of both eyes in opposite directions to obtain or maintain single binocular vision
  3. Bilateral relaxation of the lens
    the lens becomes spherical due to contraction of the ciliary muscles (CNs III)
57
Q

Name and describe the three types of lacrimation

A
  1. Basal tears (important in corneal health)
    - Clean/nourish & hydrate the avascular cornea
    - Contain lysozyme (an enzyme that can hydrolyse bacterial cell walls)
  2. Reflex tears (extra tears in response to mechanical or chemical stimulation)
    - The afferent limb of the reflex is CN V1 (the ophthalmic nerve) from the cornea/conjunctiva
    - The efferent limb is parasympathetic axons originating from CN VII (the facial nerve)
  3. Emotional tears (happy, sad or frightened tears)
58
Q

What are the two types of humour found in the eye and where is each found?

A
  1. Aqueous humour
    - Fills up anterior portion of eye
    - Divided into posterior – behind iris
    - Anterior – in front of the iris
  2. Vitreous humour presses up on the outside of the eyeball and helps to maintain its shape
59
Q

Describe the pathway of aqueous humour from secretion to absorption.
Blockage of this pathway can lead to which condition?

A
  • Ciliary processes secrete aqueous humour
  • Floats into posterior chamber (behind iris)
  • Circulates between lens and iris, then through pupil
  • Passes into anterior chamber
  • Absorbed at irido-corneal junction
    Any blockage to this area which prevents circulation of aqueous humour may lead to glaucoma
60
Q

What is the Munro-Kellie hypothesis?

A

If one increases, then something else must have to give way – Munro-Kellie hypothesis
Describes relationship between volume and pressure in the skull

61
Q

What is the Sunset sign?

Which condition is it seen in?

A

Whites of eyes showing above iris

Hydrocephalus

62
Q

What are the three layers of the meninges?

Briefly describe each.

A

Outer = dura mater = stiff, fibrous, doesn’t expand – end osteal and meningeal layers
Middle – thin membrane which looks like a spider web – very thin + see-through
Inner – unicellular thick layer which surrounds the brain itself

63
Q

Name and describe the two layers of the dura mater

A

The dura mater has two layers

  • Falx cerebri – separates the cerebral hemispheres, bends of over to form a fold
  • Tentorium – second fold that holds the cerebrum up off of the cerebellum
64
Q

What is the function of:

  • Tentorium cerebelli
  • Falx cerebelli
A

Tentorium cerebelli - separates cerebellum from hemispheres

Falx cerebelli - separates the two hemispheres of the cerebellum

65
Q

What is the tentorial notch?

A

Tentorial notch = space in tentorium – with raised ICP the brain can be forced into this space

66
Q

What is the name given to the space between two layers of the meninges through which venous blood flows?

A

Dural venous sinuses

67
Q

Name each of the ventricles found in the brain

A 
Lateral ventricles (two)
- Body
- Frontal (anterior) horns
- Occipital (posterior) horns
- Temporal (inferior) horns
Third ventricle
- Between thalami
- Very flat
Fourth ventricle
- Between pons/medulla and cerebellum
68
Q

Where is CSF produced?

A

CSF is produced in the choroid plexus – layer which surrounds all of the ventricles, but most in the fourth ventricles

69
Q

Describe the steps in CSF circulation from production to reabsorption

A
  • CSF is produced in the choroid plexus – layer which surrounds all of the ventricles, but most in the fourth ventricles
  • Two lateral ventricles
  • Interventricular foramen
  • Third ventricle
  • Cerebral aqueduct
  • Fourth ventricle
  • -> some to central canal of spinal cord
  • Median or two lateral apertures
  • Subarachnoid space
  • Arachnoid villi
  • Superior sagittal sinus
  • Reabsorption into venous system
70
Q

What causes a pupil to dilate in terms of raised ICP?

A

Pressure on CN III – unopposed sympathetic action of the dilator pupillae

71
Q

How does raised ICP affect the optic nerve?

A

Optic ‘nerves’ are actually CNS tracts
- Covered by meninges
Raised ICP increases pressure in the sub-arachnoid space - affects the optic nerve
Also compresses the central artery and vein of the retina

72
Q

What is the name given to swelling of the optic disc?

A

Papilloedema

73
Q

Describe the grades of papilloedema

A

Grade I - C shaped halo, blurring of edge of disc
Grade II - Circumferential halo with blurred edges
Grade III - Vessels on EDGE of disc disappear
Grade IV - Loss of major vessels ON disc
Grade V - Extremely blurred edges and total or partial obscuring of vessels on disc

Ophthalmology (9 decks)

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