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Head, Neck And Neuro > Anatomy of the eye > Flashcards

Anatomy of the eye Flashcards

1
Q

What are the three layers of the eye?

A

Retina
Fibrous tunic
Vascular tunic

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2
Q

What are the layers of the fibrous tunic?

A

Superficial layer
Anterior cornea
Posterior sclera
Junction of sclera and cornea

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3
Q

Describe the cornea.

A

Transparent coat that covers the iris
Curved to help focus light on the retina
The central parts of the cornea receives oxygen from the outside air - contacts must be permeable to allow oxygen through them

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4
Q

Describe the components of each layer of the cornea.

A

Outer surface consists of non-keratinised stratified squamous epithelium
Middle coat - collagen fibres and fibroblasts
Inner coat - simple squamous epithelium

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5
Q

Describe the sclera.

A

The white of the eye
A layer of dense connective tissue composed of collagen fibres and fibroblasts
Covers the whole eye ball except the cornea - gives the eyeball shape and makes it rigid (protects the inner parts)
An attachment site for extrinsic eye muscles

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6
Q

What is found in the junction of the sclera and cornea?

A

Sclera like venous sinus - aqueous humour drain into this

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7
Q

What is the function of the fibrous tunic?

A

Mechanical support and physical protection
Attachment site for extrinsic eye muscles
Assists focusing

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8
Q

What are the components of the vascular tunic?

A

Choroid
Ciliary body
Iris

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9
Q

What is the most posterior part of the vascular tunic?

A

Choroid

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10
Q

Where is the choroid in relation to the sclera?

A

Lines the internal surface of the sclera

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11
Q

Why does the choroid appear dark brown?

A

Contains melanocytes that produce high quantities of melanin

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12
Q

Why does the choroid contain such high quantities of melanin?

A

So it absorbs lots of light rays, preventing reflection and scattering of the light within the eyeball
- causing the image to be cast on the retina by the cornea to remain sharp and clear

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13
Q

What happens to the choroid in the anterior portion of the vascular tunic?

A

It becomes the ciliary body

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14
Q

Where is the ciliary body?

A

It extends from the jagged anterior margin of the retina (or a serrata) to just posterior to the junction of the sclera and cornea

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15
Q

What are the two parts of the ciliary body?

A

Ciliary processes and ciliary muscle

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16
Q

Describe the ciliary processes

A

Protrusions or folds in the inner surface of the ciliary body
Contains blood capillaries that secrete aqueous humour

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17
Q

What are zonular fibres?

A

Fibres that extend from the ciliary process to the lens

The fibres consists of thin, hollow fibrils that resemble elastic connective tissues fibres

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18
Q

What is the ciliary muscle, and what is its function?

A

Circular band of smooth muscle
Contraction and relaxation of this muscle changes the tightness of the zonular fibres, which alters the shape of the lens, adjusting it for near or far vision

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19
Q

Where is the iris located?

A

Suspended between the cornea and the lens attached to the ciliary processes on its outer margin

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20
Q

What does the iris contain?

A 
Blood vessels
Pigment cells
Loose connective tissue
Circular and radical smooth muscle fibres 
Melanocytes
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21
Q

What does the amount of melanin in the iris dictate?

A

Eye colour

  • large amounts of melanin = brown or black eyes
  • moderate amounts of melanin = green eyes
  • low amounts of melanin = blue eyes
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22
Q

What is the function of the iris?

A

Regulates the amount of light entering the eyeball through the pupil

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23
Q

Why does the pupil appear black?

A

It shows the inside of the eye

- heavily pigmented choroid and retina can be seen

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24
Q

Why is light reflected (e.g. In photos) from the eyeballs seen to be red?

A

Blood vessels on the surface of the retina

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25
Q

When bright light stimulates the eye, what happens to the pupil, and how?

A

Parasympathetic fibres of CN III stimulate the circular muscles (sphincter pupillae) of the iris to contract
Pupil constriction occurs

26
Q

When dim light simulates the eye, what happens to the pupil, and how?

A

Sympathetic nerves stimulates the radical muscle (dilator pupillae) of the iris to contract
The pupil becomes dilated

27
Q

What enters and leaves the eye at the optic disc?

A

Optic nerve
Central retinal artery (branch of the ophthalmic artery)
Central retinal vein

28
Q

What is the name of the two layers of the retina?

A

Pigmented layer

Neural layer

29
Q

What is the pigmented layer of the retina, and where is it located?

A

A sheet of melanin-containing epithelial cells found between the choroid and the neural part of the retina

30
Q

What is the function of the pigmented layer of the retina?

A

Melanin in this layer helps absorb stray rays of light

31
Q

What is the neural layer of the retina?

A

Multilayered outgrowth of the brain

32
Q

What is the function of the neural layer of the retina?

A

Processes visual data extensively before sending nerve impulses into the axons that form the optic nerve

33
Q

What are the three layers that form the neural part of the retina?

A

Photoreceptive layer
Bipolar cell layer
Ganglion cell layer

34
Q

What are the two zones that separated the three layers of the neural part of the retina?

A

Outer an inner synaptic layers

35
Q

Which order does light pass through the neural layer of the retina?

A 
Ganglion cell layer
Inner synaptic layer
Bipolar cell layer
Outer synaptic layer 
Photoreceptive layer
36
Q

Name the two other cell types present in the bipolar layer, and what do they do?

A

Amacrine cells
Horizontal cells
They regulate communications between the rods/cones and ganglion cells
- helps adjust retinal sensitivity to dim/bright light
- changes the contrast

37
Q

List the order of the layers from the outer layer of the eye, to the optic nerve axons on the inside.

A

Sclera
Choroid
Pigmented layer of the retina
Photoreceptive layer of the neural layer of the retina
Bipolar cell layer of the neural layer of the retina
Ganglion cell layer of the neural layer of the retina
Optic nerve axons

38
Q

What are the two types of photoreceptors?

A

Cones and rods

39
Q

What is the function of the rods?

A

Allow vision in dim light (no colour vision)

  • black, white and all shades of grey
  • very light sensitive
40
Q

What is the function of the cones?

A

Stimulates by brighter lights

  • three types of cones = red, green and blue
    • various combinations of these cones result in colour vision
  • gives sharper and clearer images
  • doesn’t see as well in dim light
41
Q

Describe the cone and rod distribution of the eye.

A

Cones are found in greater concentrations at the back of the eye, and rods are found round the sides

42
Q

What is the area of the eye with the highest concentration of cones called?

A

The macular densa

43
Q

Why is the optic disk a blind spot?

A

Contains no cones or rods

44
Q

Describe the fovea centralis

A

A small depression in the centre of the macular densa which contains only cones
- area of highest visual acuity

45
Q

What makes up the refractive media of the lens?

A

Proteins called crystalline within the lens

  • arranged like layers in an onion
  • perfectly clear and transparent
46
Q

What is the outer covering of the lens?

A

Clear connective tissue

47
Q

What is the function of the lens?

A

Helps the focus the image on the retina by changing its own shape
- facilitates clear vision

48
Q

What are the two cavities within the eyeball called?

A

The anterior and posterior cavity (or vitreous chamber)

49
Q

What are the two chambers within the anterior cavity?

A

Anterior and posterior chambers

50
Q

Where is the anterior chamber?

A

Between the cornea and the iris

51
Q

Where is the posterior chamber?

A

Between the iris and the zonular fibres and lens

52
Q

What is the contents of the anterior cavity?

A

Aqueous humour - transparent watery fluid which nourishes the lens and the cornea

53
Q

How does the aqueous fluid enter and leave the anterior cavity?

A

Continually filters out from capillaries in the ciliary processes of the ciliary body - entering the posterior chamber
It flows between the iris and the lens, through the pupil and into the anterior chamber
It then drains into the scleral venous sinus from the anterior chamber and into the blood

54
Q

How often is aqueous humour replaced?

A

Completely replaced every 90 minutes

55
Q

Where is the vitreous chamber?

A

Between the lens and the retina

56
Q

Describe the vitreous fluid, and it’s function.

A

A transparent jelly-like substance that holds to retina flush against the choroid
- gives the retina an even surface for the reception of clear images

57
Q

What are the components of the vitreous body?

A

Water, collagen fibres, hyaluronic acid and phagocytes (to keep this part of the eye free from debris for uninterrupted vision)

58
Q

What is the hyaloid canal?

A

A narrow channel (inconspicuous in adults) that runs through the vitreous body from the optic disk to the posterior aspect of the lens

59
Q

What is the pressure in the eye called, and what is it normally?

A

The intraocular pressure is normally 16mmHg

60
Q

Which component on the eye produces the intraocular pressure, and why is it needed?

A

The pressure is mainly produced by the aqueous humour and only partly by the vitreous body.
It’s needed to maintain the shape of the eyeball and prevent collapse

Head, Neck And Neuro (19 decks)

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