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H&N Z > 5 Components of the Eyeball > Flashcards

5 Components of the Eyeball Flashcards

1
Q

What are the 3 layers of the eyeball?

A

Fibrous
Vascular
Inner (retinal)

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2
Q

What are the components of the fibrous layer. Describe and give function.

A

Sclera
- Provides attachment for extra ocular muscles

Cornea

  • Anterior and centre
  • Transparent
  • Refracts light entering eye
  • Corneal reflex (Tactile/thermal/pain stimulation –> CNV1 –> CNVII –> Orbicularis oculi –> involuntary blink)

Function:
Shape and support

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3
Q

What are the components of the vascular layer?

A

Choroid
Ciliary body
Iris

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4
Q

What is the choroid? Function?

A

Layer of CT and blood vessels in vascular layer.

Provides outer retina with nourishment.

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5
Q

What is the ciliary body made up of? Function?

A

Ciliary smooth muscle fibres connected to lens via ciliary processes.

Control the shape of the lens.
Formation of aqueous humour for the anterior chamber.

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6
Q

What is the iris? Where is it?

A

Circular diaphragm with aperture - pupil.
Between lens and cornea
Smooth muscle fibres control the size of the pupil.

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7
Q

What are the components of the retina? Location?

A

Neural layer (posterior lateral)

Pigmented later
Underneath neural layer, attached to choroid, continues around inner surface.

Fundus
Posterior eye

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8
Q

What is the optic part of the retina? What does it contain?

A

Both neural and pigmented layers present.
Contains macula (centre of retina)
This contains fovea (depression n macula)
High density photo receptors.

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9
Q

What is the fovea responsible for?

A

High acuity vision.

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10
Q

What is the neural layer made up if?

A

Light detecting cells, photoreceptors
Rods - low light
Cones - bright light.

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11
Q

Where is the blindspot of the eye?

A

Fundus

Optic disc - where CNII enters the eye

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12
Q

What is the function of the pigmented layer? What is the anterior part called?

A

Supports neural layer - continues round inner surface of the eye
Anterior part = non-visual retina.

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13
Q

What are myopia, hyperopia and presbyopia?

A

Myopoa - short/near sighted (image focused in front of retina)

Hyperopia - long/far sighted
(image focused behind retina)

Presbyopia - Far sight due to age related changes of the lens. (Lens become thicker)

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14
Q

What is aqueous humour? Where is it produced/drained?

A

Transparent watery fluid filling chambers of the eye.
Produced by ciliary processes
Drains into scleral venous sinus via trabecular meshwork.
Responsible for maintaining intraocular pressure.

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15
Q

What is the lens?

A

Transparent, biconcave structure enclosed in capsule behind the iris, attached to ciliary body by suspensory ligaments.
Contraction of ciliary muscle fibres changes shape of lens.

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16
Q

How does the lens change for near and far vision?

A

Near vision
Accommodation
Ciliary muscles stimulated by parasympathetics (short ciliary nerves from CNIII) make lens more globe like/fatter.

Far vision
No parasympathetic stimulation to ciliary muscles resulting in flatter, stretched lens.

17
Q

What is vitreous humour? Function?

A

Jelly like substance filling the cavity behind the lens.
Supports lens
Holds retina in place.

18
Q

What are the chambers of the eye? Boundaries? What do they contain.

A

2 fluid filled areas in the eye

Anterior chamber:
Between cornea and iris

Posterior chamber
Between iris and ciliary processes.

Aqueous humor
Clear plasma like fluid that nourished and protects the eye.
Produced by ciliary processes constantly.
Drains via trabecular meshwork to the base of the cornea.

19
Q

What happens if the corneal reflex is absent?

A

Corneal ulceration

Foreign particles not felt –> infection

20
Q

What is the arterial supply of the eye? What happens in obstruction?

A

ICA - Ophthalmic artery - Central artery of the retina

If obstructed by thrombus instant painless loss of vision as it si an end artery (due to ischaemia)

21
Q

What is the venous drainage of the eye? What happens in occlusion?

A

Retinal vein –> Superior/inferior ophthalmic veins –> Cavernous sinus

(infection can spread from eye to brain)

Occlusion causes slow painless loss of vision.

22
Q

What are the functions of the eyelids?

A

Protect from light and injury.
Prevent corneal drying through spread of lacrimal fluid across surface.
Dust and foreign material is swept to the medial angle of the eye and removed.

23
Q

What are the tarsal plates and tarsal glands?

A

Tarsal plates:
Dense bands of CT that contain tarsal glands

Tarsal glands
Behind eyelashes within the tarsal plate.
Produce secretions that lubricate the edges of eyelids, preventing them from sticking together.

24
Q

What muscles open the eyelid? Innervation?

A

Levator palpebrae superioris - CNIII (sperior)

Superior tarsal msucles (sympathetic)

25
Q

What happens if the muscles opening the gelid are paralysed?

A

LPS - ptosis (drooping of upper eyelid)
May be residual opening capacity due to superior tarsal muscles
Vision compromised

Superior tarsal msucles
Partial ptosis (minor drooping)
Vision OK
Horner’s syndrome

26
Q

What muscles close the eyelid? Inenrvation?

What happens in paralysis?

A

Orbicularis oculi only
CNVII

Failure to close eyes
Bell's palsy
Loss of blink
Lsos of corneal reflex
Dry eyes
Weakness of OO - lower eyelid falls away so pooling of tears in lower fornix
Infection
Lack of corneal protection/lubrication - corneal ulceration.
27
Q

What do the lacrimal glands secrete? What is the function of this? What stimulates this?
Where are they located?

A

Secrete lacrimal fluid
Watery physiological saline
Bacteriocidal lysosyme
Moistens and lubricates surface of conjunctiva
Provides nutrients and dissolved O2 to cornea

Stimulated by parasympathetics from superior salivatory nucleus via greater petrosal nerve, pterygopalatine ganglion, Zygomatic CNV2, lacrimal CNV1.

Located superolateral to eye,

28
Q

What is the path of lacrimal fluid?

A

LAcrimal glands
Lacrimal ducts conduct fluid from glands to conjunctival sac.
Lacrimal cannaliculi commense at medial angle of eye where lacrimal fluid is drained from the lacrimal lake into the lacrimall sac.
Nasolacrimal duct
Conveys lactimal fluid into inferior nasal meatus.
Fluid is then swallowed

H&N Z (23 decks)

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