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OD1 - Integrated Ophthalmic Sciences & Preclinical Optometry > BS - Connective Tissue, Sclera and Vitreous - Week 1 > Flashcards

BS - Connective Tissue, Sclera and Vitreous - Week 1 Flashcards

1
Q

Where does connective tissue originate embryonically? What are the origins of the corneal stroma?

A

Most connective tissue is mesoderm-derived.

Corneal stroma is ectoderm-derived.

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2
Q

What is connective tissue made of?

A

Cells and extracellular matrix.

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3
Q

What kind of connective tissue is the conjunctiva?

A

Loose

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4
Q

What kind of connective tissue is the sclera?

A

Dense regular

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5
Q

What kind of connective tissue is the tarsal plate?

A

Dense irregular

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6
Q

What kind of connective tissue is the episclera?

A

Loose

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7
Q

What kind of connective tissue is the cornea?

A

Dense regular

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8
Q

Can adipose tissue be considered connective tissue? Give an example of adipose relating to the eye.

A

Yes, it is a specialised form of connective tissue.

Orbital fat.

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9
Q

Name the 4 main functions of connective tissue.

A 
Primary function is structural support
Additonal functions are:
Defence and protection of the body
Fat storage
Medium of exchange for waste and resources (oxygen and nutrients)
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10
Q

Name one function of connective tissue that is specific to the eye.

A

Light refraction (cornea).

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11
Q

Which form of connective tissue is responsible for acting as the medium of exchange for waste and resources?

A

Loose connective tissue

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12
Q

What is the extracellular matrix composed of primarily?

A

Ground substance and fibres.

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13
Q

What is the ground substance of the ECM made of? Is it organised or disorganised?

A

Made of specialised glycosaminoglycans, glycoproteins, and proteoglycans.
Highly organised interfibrillar matrix.

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14
Q

What are the three main components of fibres within the ground substance of the ECM?

A

Primarily collagen
Also elastic fibres - elastin and fibrillin
Reticular fibres

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15
Q

What are reticular fibres?

A

Small collagen fibres

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16
Q

What are glycosaminoglycans?

A

Repeating dissacharide units of amino sugar and uronic acid.

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17
Q

What are glycoproteins?

A

Proteins conjugated to saccharides lacking a serial repeat unit.

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18
Q

What 3 functions of glycosaminoglycans make it an important component of connective tissue?

A

Attracts water

Confers viscosity for resistance to pressure

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19
Q

Are all glycosaminoglycans charged? What charge do they carry?

A 
All but one class carry a negative charge due to the presence of sulphur groups.
Hyaluronic acid lacks sulphur, and is neutral - unique.
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20
Q

What cell is present in all connective tissue, and why?

A

Fibroblasts, as they make collagen.

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21
Q

How does connective tissue appear histologically?

A

Amorphous, due to the fixation process - doesn’t mean the space is empty however.

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22
Q

Can hyaluronic acid attract water, being a glycosaminoglycan?

A

Alone, it cannot as it is not sulphonated like other GAGs. It instead associates with other GAGs.

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23
Q

What are proteoglycans? What structure do they have, and what charge?

A

Heavily glycosylated glycoproteins.
They are a core protein, with one or more covalently attached GAG chains.
They are therefore negatively charged.

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24
Q

What is the function of charge on proteoglycans? What does this allow for?

A

The negative charge allows it to bind to cations like Na, K, and Ca. Allows control over matrix hydration.

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25
Q

How does hydration affect fibres in connective tissue?

A

Hydration controls fibre separation.

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26
Q

How does hyaluronic acid complex with other proteins?

A

One hyaluronic acid associates with many core proteins via a link protein. The core proteins may have many sulphonated GAGs.

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27
Q

Is collagen elastic?

A

Often referred to as inelastic.

Is actually highly elastic.

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28
Q

In what form is collagen typically found?

A

As fibre bundles comprising fibrils.

29
Q

Do collagen fibres have uniform diameters?

A

Typically is relatively uniform, howver in different locations, and at different stages of development, may vary in size.

30
Q

What is the most abundant protein in the animal kingdom?

A

Collagen.

31
Q

How many kinds of collagen are there?

A

28 types.

32
Q

What structure does collagen have?

A

Is a triple-helix of 3 fibrils.

33
Q

In the eye, where is type I collagen found? What structure does it have?

A

Cornea and sclera

Is fibrillar

34
Q

In the eye, where is type II collagen found?

What structure does it have?

A

Vitreous

Is fibrillar

35
Q

In the eye, in what two structures is type IV collagen found?
What structure does it have?

A

ILM of the retina
Is a sheet
Also the major collagen component of zonule fibres

36
Q

In the eye, where is type V collagen found?

What structure does it have?

A

Cornea

Is fibrillar

37
Q

In the eye, where is type VI collagen found?

What structure does it have?

A

Cornea

Fibril-associated

38
Q

In the eye, where is type VII collagen found?

What structure does it have?

A

Hemidesmosomes in the cornea

Is anchoring

39
Q

What are the four main types of elastic fibres, and what confers this elasticity?

A 
Elastin (main)
Fibrillin
Fibronectin
Laminin
Elasticity due to unusual polypeptide backbone of random coiled molecules
40
Q

Where are elastic fibres typically found in the connective tissue?

A

Interwoven amongst collagen microfibrils.

41
Q

What are reticular fibres?

A

Delicate network of fibres composed of collagen fibrils, but of different composition.
Small diameter, and do not form bundles.

42
Q

What collagen type is localised to reticular fibres?

A

Type III.

43
Q

Name 5 exampes of fixed cells in connective tissue?

A 
Fibroblasts
Pericytes
Adipose
Macrophages
Mast cells
44
Q

What is the function of fibroblasts?

A

Synthesise collagen, elastic, and reticular fibres

45
Q

Where are myofibroblasts found?

A

Stressed tissue like the cornea.

46
Q

What are pericytes?

A

Cells that surround endotheial cells of small blood vessels.

47
Q

Where are mast cells derived from?

What is characteristic of them?

A

Stem cells in the bone marrow.

Have granules with histamine, heparin, and factors for initiating an inflammatory response.

48
Q

What are transient cells in connective tissue typically associated with? Where are they derived from?

A

Immune system activation and inflammation. Derived from stem cells in the bone marrow.

49
Q

What are the 6 functions of the sclera?

A 
Protection
Refractive stability
Conduit for neurovascular vessels
Anchor for extraoccular muscles
Anchor for cilliary muscles
Facilitates ocular drainage
50
Q

What are the two major foramina of the sclera?

A

Anterior - cornea

Posterior - scleral canal

51
Q

Where is the minor foramen of the sclera?

A

The optic disc where the neurovascular bundle pierces the sclera

52
Q

What is the orientation of the scleral fibre bundles at the scleral canal? What purpose does this have?

A

2/3rds of the fibres turn 90 degrees forming meninges.

Remaining 1/3rd continues forming a mesh-like structure providing support to the nerve bundles.

53
Q

What is the lamina cribrosa?

A

Sieve of interwoven collagen fibres whose chief purpose is to support the optic nerve bundle at the scleral canal.

54
Q

Where is the weakest part of the outer eye, and when is this apparent?

A

Lamina cribrosa/scleral canal, affected most when intraoccular pressure is high.

55
Q

What is Tenon’s capsule, what is its name in latin, what does it enclose, and where does it terminate anteriorly/posteriorly?

A

Fascia bulbi, a thin membrane enclosing the extraoccular muscles and episclera posteriorly.
Terminates at the limbal conjunctiva anteriorly, and optic nerve posteriorly.

56
Q

What does the fascia bulbi merge with, and where?

A

Merges with the conjunctival tissue anteriorly.

57
Q

What is the episclera?

A

Loose vascularised connective tissue overlying the sclera, connecting posteriorly to fascia bulbi via fine strands.

58
Q

What is the scleral stroma?

A

Dense fibrous tissue intermingles with fine elastic fibres.

59
Q

What is the limbal region?

A

Junction where the sclera, overlying episclera, and overlying conjunctiva meet the cornea.

60
Q

What is the maina fusca also known as? What colour is it, and what is it attached to, and how?

A

Suprachoroid, brown in colour.

Attached to the choroid by fine collagen fibres.

61
Q

What two structures does the perichoroidal space seperate?

A

Choroid from the suprachoroid.

62
Q

What is the fibre bundle organisation in the sclera?

A

They run in whorls, interwoven for strength.

63
Q

What is the purpose of varying sizes of cllagen fibril diameters?

A

Large diameters provide strength, low diameters provide flexibility and allow for tight packaging.

64
Q

Why is the sclera opaque, and what is the advantage of this?

A

Irregular fibril sizes and bundle orientation.

Opacity means less stray light entering the eye.

65
Q

What are the three main functions of the vitreous?

A

Shock absorber, protecting the retina and lens
Internal tamponade preventing retinal tears
Mainenance of a globe shape for image stability

66
Q

Which type of collagen is typically found in vitreous?

A

Type II

67
Q

What is the vitreous primarily composed of?

A

99% water, rest includes collagen, and hyaluronan

68
Q

What 3 features of the vitreous allow for decreased light scattering?

A

Small, regular collagen fibril diameters
Few cells
Regular interfibrillar seperation

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

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