Anatomy of Eye Flashcards

1
Q

External structure of eye

A

Sclera (outermost layer)
Choroid
Retina

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2
Q

Cornea

A
  • Main structure responsible for refraction of light entering eye
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3
Q

Layers of the cornea

A

From outermost to innermost
1. Epithelium
2. Bowman’s layer
3. Stroma
4. Descemet’s membrane
5. Endothelium
- Pumps water out of cornea to keep it dry and clear
- Number of cells decrease with age, does not regenerate
- Diseases affecting endothelium cause corneal edema and hazy cornea

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4
Q

Nerve supply of the cornea

A

Ophthalmic division of trigeminal nerve

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5
Q

Flow of aqueous humour

A
  • Produced at the ciliary body
  • Flows anterior to the lens and through the pupil
  • Drains into Schlemm’s canal (10% drains into uveo-scleral pathway)
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6
Q

Where can aqueous humour be found?

A

Anterior and posterior chamber

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7
Q

Function of aqueous humour

A
  • Maintenance of intraocular pressure and structural form of the globe
  • Provides nutrition to surrounding tissues
  • For its refractive index
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8
Q

Fovea contains which photoreceptor only?

A

Cones

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9
Q

Blood supply of the retina

A

Central retinal artery is a branch of ophthalmic artery
- supplies inner 6 layers of retina

Choroidal vessels
- supplies outer 4 layers

Retinal veins drains into cavernous sinus directly or via superior ophthalmic vein

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10
Q

Orbicularis oculi muscle

A

Function: Closure of eyelids
Nerve supply: zygomatic branch of facial nerve

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11
Q

Levator palpebrae superioris

A

Function: elevates upper eyelid
Nerve supply: oculomotor nerve

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12
Q

Neurons at the retina

A

3 main groups of neurons: Photoreceptors (rods and cones)
- Rods for vision in dim light
- Cones for vision in bright light, fine details and colour
- Rods are absent at fovea, ↑ in
number towards peripheral retina
- Cones of highest density at fovea, ↓ in number in periphery

Bipolar cells
Ganglion cells

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13
Q

How are tears produced and drained?

A

Tears are secreted by main and accessory lacrimal gland, pass along the ocular surface and enter the upper and lower canaliculi and enters lacrimal sac and nasolacrimal duct

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14
Q

Lens

A
  • Transparent biconvex structure located behind iris and pupil and in front of vitreous body
  • Equator of lens encircled by ciliary processes of ciliary body and kept in position by suspensory ligaments
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15
Q

Accommodation of lens

A

When looking at far objects, ciliary muscles relax -> lens zonules pull on lens -> lens become flatter/less convex -> focus light from far objects onto retina

When looking at near objects, ciliary muscles contract -> lens zonules slacken -> lens become more convex -> focus light from near objects into retina

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16
Q

Blood supply of fovea

A

Choroidal arteries