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OD1 - Integrated Ophthalmic Sciences & Preclinical Optometry > BS - Microscopy, General Ocular Structure & Embryology - Week 1 > Flashcards

BS - Microscopy, General Ocular Structure & Embryology - Week 1 Flashcards

1
Q

What charge does haemotoxylin have, and what colour does it stain?

A

A basic dye with a positive charge, staining purple.

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2
Q

What can haemotoxylin be used to stain?

A 
Heterochromatin, RER, nucleolus, and the nucleus.
Also GAGs (theyre negative).
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3
Q

What charge does eosin have, and what colour does it stain?

A

An acidic dye with a negative charge, staining pink.

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4
Q

What can eosin be used to stain?

A

Most cytoplasmic filaments, intracellular membranous components, collagen/elastin, and the cytoplasm.

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5
Q

What stain can be used to dye carbohydrates?

A

PAS

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6
Q

What stain can be used to dye mast cell granules?

A

Toluidine blue

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7
Q

What does methylene blue stain?

A

Cell body, cytoplasmic extensions, and nuclei.

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8
Q

Which stain can be used to differentiate muscle and collagen fibres?

A

Masson’s stain

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9
Q

Which stain can be used to differentiate muscle and connective tissue?

A

Van Gieson

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10
Q

Explain how a phase contrast microscope works.

A

Different components have different refractive indices. Exploits this to resolve an image.

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11
Q

Explain how a dark field microscope works.

A

Only scattered or diffracted light reaches the objective lens. Particles reflecting light appear bright against a dark background.

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12
Q

What are two ways fluorescence microscopy can be done?

A

Autofluorescence - detect naturally fluorescing molecules

Can attach a fluorescent marker beforehand, and expose to UV

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13
Q

With transmission electron microscopy, which areas appear bright, and which appear dark?

A

If the electron passes through, it appears bright, if they are absorbed by the specimen, it appears dark.

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14
Q

How is Clarity imaging carried out?

A

Hydrophilic polymers are used to fixate the tissue, while the fats that obscure imaging are removed.
Complete structural analysis can then be done.

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15
Q

Define zygote.

A

Fertilised ovum.

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16
Q

Define morula.

A

Solid mass of cells, formed by the zygote undergoing cell division on its way to the uterus.

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17
Q

When does a cavity appear during embryogenesis, what is it called, and what is the inner cell mass called?

A

Cavity appears at day 5-6, called blastocyst cavity.

The inner cell mass is called the embryoblast.

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18
Q

What differentiates into the embryo?

A

Embryoblast

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19
Q

What encloses the blastocyst cavity? What does it differentiate into?

A

Trophoblast, forming the placenta and support tissue

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20
Q

What does the blastocyst implant into, and when?

A

Impants into the endometrium of the uterus, around day 5-6.

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21
Q

Define gastrulation and when it occurs.

A

Process of proliferation and migration of inner cells to different regions, at the beginning of week 2.

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22
Q

What two cavities appear during gastrulation? What are they lined by?

A

Amniotic cavity - lined by the epiblast

Yolk sac - lined by the hypoblast

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23
Q

At the beginning of gastrulation, flat discs of cells form what?

A

Bilaminar germ disc

24
Q

What happens during the third week (gastrulation)? What happens to the epiblast, hypoblast, and bilaminar disc?

A

Primitive streak and knot form.
From there, epiblast cells detach and migrate laterally to the space between the epiblast and hypoblast.
Trilaminar disc forms.

25
Q

What are the three types of tissue formed during the third week, what do they give rise to, and where do they originate from?

A

Endoderm - lining of the gut, arising from the hypoblast
Ectoderm - skin and nervous sytem, arising from the epiblast
Mesoderm - connective tissue, arising from epiblast cells that detached during the formation of the primitive streak

26
Q

How do the eye and nervous system relate?

A

The eye is an extension of the nervous system.

27
Q

What does the eye originate from embryologically (name 4)?

A

Surface ectoderm
Neural ectoderm
Neural crest cells
Mesoderm

28
Q

When does the primitive streak form?

A

Week 3

29
Q

What does the notochord bud from?

A

Primitive node.

30
Q

Where is the primitive node found?

A

Caudal end of the primitive streak.

31
Q

What does the notochord formation induce?

A

Neural plate formation

32
Q

How does the neural plate form?

A

Surface ectoderm thickens in the mid-periphery.

33
Q

What happens to the neural plate at day 19?

A

Central depression forms, called neural groove

34
Q

What happens to the neural groove at day 20?

A

Lateral walls of the grooves grow to form neural folds.

These continue growing towards each other to meet and form the neural tube.

35
Q

Which region do the neural folds meet to form the neural tube?

A

Mid-region, and progresses in both directions.

36
Q

Where do neural crest cells originate from?

A

From the neuroectoderm at the crest of the neural folds.

37
Q

What is the mesenchyme, and where does it arise from?

A

Arises from neural crest cells that mingle with mesoderm cells to form the mesenchyme which surrounds the neural tube.

38
Q

What mainly forms the connective tissue of the eye?

A

Mesenchyme

39
Q

When does the neural tube close?

A

At 3.5 weeks

40
Q

When do optical vesicles appear, where do they appear from, and how do they connect with the general neural structure?

A

They appear at 3.5 weeks, appearing as hollow outgrowths from each side of the forebrain.
They remain in contact with the forebrain via the optical stalk.

41
Q

What is the embryological optic nerve?

A

Optical stalk

42
Q

When and how does the lens placode form, and what does this result in the formation of?

A

At day 27, the surface ectoderm overlying the optical vesicles thicken and push inward, forming the lens placode.
Results in the formation of the optic cup.

43
Q

Concerning the optic cup and the lens placode, what happens by day 36?

A

The two folds forming the lens placode meet (similar to the neural folds, but circular, not linear) and merge, forming the lens vesicle, surrounded by the optic cup.
Part of the optic cup eventually becomes the neural retina.

44
Q

How does the vitreous form, which cells are involved, and what do they penetrate?

A

Mesenchymal cells penetrate into the optic cup and form the vitreous.

45
Q

What vessel supplies blood to the optic cup? Where does it enter from, and what is it a branch of?

A

The hyaloid vessels supply the optic cup via the choroidal fissure. It is a branch of the ophthalmic artery.

46
Q

What eventually happens to the choroidal fissure, and when? What happens to the vessels within?

A

The choroidal fissure fuses by week 6, and the vessels within become the central retinal artery/vein.

47
Q

What is coloboma, and what does it result in?

Name some physical changes to the eye as a result of this, and what this depends on.

A

Failure of the choroidal fissure to fuse by week 6.
Means absence of part or all of a tissue.
Physical appearance depends on where it fails to close. Some changes include:
-Keyhole pupil at the iris (Madeleine McCann)
-Loss of part of the eyelid (superior not inferior)

48
Q

How many cells thick is the lens vesicle, and what is it surrounded by?

A

One cell thick, surrounded by the basal lamina.

49
Q

What does the lens vesicle eventually form? Which end thickens? What do cells on this end form, and what do they produce? How long does this process take?

A

The lens. Cells at the posterior surface elongate, forming primary lens fibres. They produce crystalline proteins. After 45 days, lens vesicle is filled with primary lens fibres.

50
Q

What signals for the development of the lens vesicle?

A

Fibroblast growth factor from the neural retina.

51
Q

What do the primary lens fibres eventually form? Why is this so?

A

Eventually forms the embryonic nucleus due to the division of the anterior epithelial cells - the secondary lens fibres, which eventually extend around the primary fibres.

52
Q

How do the secondary lens fibres eventually meet? How are they initially?

A

In a Y shaped suture line.
Anteriorly is Y
Posteriorly is ⅄
Initially they are vertical anteriorly, and horizontal posteriorly

53
Q

At what week do sutures of the lens form?

A

8.5

54
Q

Which direction do new lens fibres migrate towards?

A

Anterior surface.

55
Q

Define leukocoria.

A

Congenital form of cataracts

56
Q

Aside from leukocoria, name another cause of congenital cataracts. Name when the greatest susceptibility of the lens occurs.

A

Infection of a mother with rubella whilst pregnant.

Greatest susceptibility of lens cells occurs before the lens capsule forms.

OD1 - Integrated Ophthalmic Sciences & Preclinical Optometry (123 decks)

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