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Neuroanatomy > Eye > Flashcards

Eye Flashcards

1
Q

Three main pathways by which structures can enter and leave the orbit

A

Optic canal

Superior orbital fissure

Inferior orbital fissure

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2
Q

Optic canal transmits

A

Optic nerve and ophthalmic artery

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3
Q

Superior orbital fissure transmits

A

Oculomotor nerve (III), Trochlear nerve (IV), Abducens nerve (VI), Ophthalmic (V1) nerve. Superior ophthalmic vein

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4
Q

Inferior orbital fissure transmits

A

Zygomatic branch of the maxillary V2 nerve, inferior ophthalmic vein and sympathetics

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5
Q

Seven extraocular muscles

A

The levator palpebrae superioris, superior rectus, inferior rectus, medial rectus, lateral rectus, inferior oblique and superior oblique.

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6
Q

Levator palpebrae superioris

A

Raising the superior eyelid. Oculomotor nerve (CN III).

The superior tarsal muscle (located within the LPS) is innervated by the sympathetic nervous system.

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7
Q

Superior rectus

A

Elevation of eyeball, oculomotor nerve

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8
Q

Inferior rectus

A

Depression of eyeball, oculomotor nerve

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9
Q

Medial rectus

A

Medial movement (adduction), oculomotor nerve

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10
Q

Lateral rectus

A

Lateral movement (abduction), abducens nerve

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11
Q

Superior oblique

A

Depresses, lateral abduction, medial rotation, Trochlear nerve

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12
Q

Inferior oblique

A

Elevates, medial adduction, lateral rotation, oculomotor nerve

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13
Q

Lacrimal gland is

A

A compound tubuloacinar gland, comprised of lobules – which are formed by multiple acini. The acini contain serous cells and produce a watery serous secretion (lacrimal fluid).

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14
Q

Lacrimation reflex

A

When something irritates the conjunctiva or cornea of the eye, the lacrimal reflex causes nerve impulses to pass along the ophthalmic branch of the fifth cranial nerve (trigeminal V1) and reach the midbrain.

The efferent limb of this reflex arc is parasympathetic facial (VII) via the pterygopalatine ganglion.

These nerve fibres stimulate the lacrimal glands of the orbit, causing the outpouring of tears.

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15
Q

Blind reflex

A

The nasociliary branch of the ophthalmic branch (V1) of the trigeminal nerve (CN V) senses the stimulus on the cornea on (afferent fiber).

The temporal and zygomatic branches of the facial nerve (CN VII) initiate the motor response (efferent fiber).

The center (nucleus) is located in the pons of the brainstem.

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16
Q

Fibrous layer of the eyeball consists of

A

Sclera (majority of the fibrous layer) and the cornea (refracts light entering the eye)

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17
Q

Cornea histology

A

External stratified epithelial layer,

Thin anterior limiting lamina (Bowman’s membrane), which is free of fibroblasts.

Then there is a thick layer of parallel running collagen fibrils, interspersed with fibroblasts, which forms the stroma of the cornea.

The inner surface of the cornea is lined by another thin membrane, the posterior limiting lamina (Descemet’s membrane)

Layer of endothelial cells.

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18
Q

The vascular layer consists of

A

The choroid, ciliary body and iris

19
Q

Choroid

A

layer of connective tissue and blood vessels. It provides nourishment to the outer layers of the retina.

20
Q

Ciliary body

A

Comprised of two parts, the ciliary muscle and ciliary processes.

Ciliary muscle - smooth muscles fibres. These are attached to the lens of the eye by the ciliary processes.

The ciliary body controls the shape of the lens, and contributes to the formation of aqueous humor

21
Q

Iris

A

Circular structure, with an aperture in the centre (the pupil).

Diameter of pupil controlled by smooth muscle fibres within the iris, which are innervated by the autonomic nervous system. It is situated between the lens and the cornea.

22
Q

Inner Layer

A

The inner layer of the eye is formed by the retina; its light detecting component.

23
Q

Retina two components

A

Pigmented outer layer

Neural inner layer

24
Q

Pigmented outer retina

A

Single layer of cells

Attached to the choroid, and supports the choroid in absorbing light (preventing scattering of light within the eyeball).

Continues around the whole inner surface of the eye.

25
Q

Neural (inner) retina

A

Consists of photoreceptors, the light detecting cells of the retina.

26
Q

Ophthalmoscopy shows

A

The centre of the retina is marked by an area known as the macula. It is yellowish in colour, and highly pigmented.

The macula contains a depression called the fovea centralis, which has a high concentration of light detecting cells.

The area that the optic nerve enters the retina is known as the optic disc – it contains no light detecting cells.

27
Q

Layers of retina, cell order

A

(inner to outer)

SCLERA

CHOROID

PIGMENTED EPITHELIUM

RECEPTOR LAYER (RODS AND CONES)

OUTER NUCLEAR LAYER

OUTER PLEXIFORM LAYER

INNER NUCLEAR LAYER

INNER PLEXIFORM LAYER

GANGLION CELL LAYER

NERVE FIBRE LAYER

28
Q

Lens

A

The lens of the eye is located anteriorly, between the vitreous humor and the pupil.

29
Q

Anterior and Posterior Chambers:

A

There are two fluid filled areas in the eye – known as the anterior and posterior chambers.

The anterior chamber is located between the cornea and the iris. and the posterior chamber between the iris and ciliary processes.

The chambers are filled with aqueous humor – a clear plasma-like fluid that nourishes and protects the eye.

30
Q

Aqueous humour drainage

A

The aqueous humor is produced constantly, and drains via the trabecular meshwork, an area of tissue at the base of the cornea, near the anterior chamber.

Schlemm’s canal is a circular lymphatic-like vessel in the eye that collects aqueous humor from the anterior chamber and delivers it into blood vessels via aqueous veins - it is covered by the trabecular meshwork.

31
Q

What happens if aqueous humour drainage is obstructed?

A

Glaucoma can result.

32
Q

Lamina cribrosa

A

Nerve fibers forming the optic nerve exit the eye posteriorly through a hole in the sclera that is occupied by a mesh-like structure called the lamina cribrosa.

Multilayered network of collagen fibers that insert into the scleral canal wall.

33
Q

Lens accommodation

A

When the ciliary muscle contracts, it pulls itself forward. This releases the tension on the lens caused by the zonular fibers.

This release of tension of the zonular fibers causes the lens to become more spherical, adapting to short range focus.

Conversely, relaxation of the ciliary muscle causes the zonular fibers to become taut, flattening the lens, increasing the focal distance, increasing long range focus.

34
Q

What do the ciliary muscles do for short range focus?

A

Contract

35
Q

What do the ciliary muscles do for long range focus

A

Relax

36
Q

Sphincter pupili role and innervation

A

Functions to constrict the pupil in bright light (pupillary light reflex) or during accommodation.

It is controlled by parasympathetic fibers of the muscarinic acetylcholine receptor (M3) that originate from the Edinger–Westphal nucleus, travel along the oculomotor nerve (CN III), synapse in the ciliary ganglion, and then enter the eye via the short ciliary nerves.

37
Q

Dilator pupili role and innervation

A

The iris dilator muscle acts to dilate the pupil.

Innervated by the sympathetic system, which acts by releasing noradrenaline, which acts on α1-receptors.

Alpha muscarinic are used to dilate the pupil

38
Q

Sphincter pupili shape

A

Circular muscles (contract and make pupil smaller)

39
Q

Dilator pupili shape

A

Radial muscles ( contract and make pupil larger)

40
Q

How does ANS affect pupil size?

A

Parasympathetic (constriction) Sympathetic (dilation)

41
Q

Arterial eyeball supply

A

The eyeball receives arterial blood primarily via the ophthalmic artery.

This is a branch of the internal carotid artery, arising immediately distal to the cavernous sinus.

42
Q

Venous drainage of eyeball

A

Venous drainage of the eyeball is carried out by the superior and inferior ophthalmic veins.

These drain into the cavernous sinus, a dural venous sinus in close proximity to the eye.

43
Q

Main fluid surrounding retina

A

Virtuous humour

44
Q

What makes optic nerve head damage and headache a common side effect of brain stem lesions

A

Papilledema

Neuroanatomy (7 decks)

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