AED - Cell Injury II - Week 1 Flashcards

1
Q

Define hypoxia.

A

Lack of sufficient oxygen to maintain normal cell function.

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2
Q

Define anoxia.

A

Total lack of oxygen

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3
Q

What is the most common cause of cell injury?

A

Hypoxia

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4
Q

List 4 causes of hypoxia.

A

Reduced atmospheric oxygen (altitude)
Relatively less RBCs in the bloodstream (leukaemia)
Abnormal haemoglobin (sickle cell disease)
Reduced blood supply (ischaemia)p

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5
Q

What is the most common cause of hypoxia?

A

Ischaemia

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6
Q

List 4 cellular consequences of ischaemic hypoxia.

A

Severe vacuolisation of mitochondria
Membrane damage
Nuclear chromatin clumping
Release of lysosomal enzymes

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7
Q

What are the three main ocular structures affected by hypoxia in the eye?

A

Cornea
Retina
Optic nerve

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8
Q

What are retinal and optic nerve hypoxia usually related to?

A

Ischaemia or other blood disorders.

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9
Q

Where does the cornea get its nutrients from?

A

Largely from the aqueous humour

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10
Q

Where does the cornea get its oxygen from (2)?

A

Atmosphere and aqueous humour

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11
Q

What are the two most common causes of corneal hypoxia?

A

Lid closure from sleep (very mild) and contact lens wear

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12
Q

Is restoration of normal oxygen levels to hypoxic tissue generally good? Explain the consequences (2).

A

Generally is good but:
-Restoration of oxygen to a tissue that contains dead or dying cells means that oxygen is initially used more vigorously by mitochondria
–Increases generation of free radicals and reduces antioxidant efficiency
-Contents of dead cells may have secondary toxic/excitotoxic effects on recovering cells leading to secondary apoptosis

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13
Q

List 7 symptoms of contact lens related hypoxia.

A

Reduced VA
Corneal oedema
Epithelial erosion (SPK)
Epithelial microcysts
Endothelial blebs
Stromal striae
Limbal neovascularisation

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14
Q

What happens to the corneal epithelium with corneal hypoxia?

A

It shrinks, despite the cornea overall swelling

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15
Q

What happens to cell-cell junctions of the corneal epithelium with hypoxia? What does this lead to?

A

They are reduced, leading to loss of cells from the surface - desquamation

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16
Q

Describe SPK.

A

Desquamation leads to areas of cell loss, where fluorescein can pool.

17
Q

What happens to the proliferative capacity of basal epithelial cells with hypoxia?

A

Reduced

18
Q

What happens to squamous cell membrane permeability with hypoxia?

A

Increases

19
Q

Explain how the corneal epithelial layer thins ith hypoxia.

A

Hypoxia causes epithelial cell injury and death
Dead cells replaced less rapidly, thinning the epithelium

20
Q

What happens to proliferative activity in the corneal epithelial layer vs the limbus? What does this imply?

A

Decreased in the epithelium, increased at the limbus.
Implies that factors released from dying cells to stimulate rapid replacement by limbal stem cells.

21
Q

What are microcysts?

A

Large structures that contain cytoplasmic and cell membrane debris

22
Q

Where do microcysts release their contents?

A

Tear film

23
Q

hat does surface microcystic activity lead to?

A

Further punctate erosions of the corneal surface

24
Q

Describe what occurs with VEGF release (3) and why it is released.

A

Hypoxic corneal epithelial cells release VEGF
Stimulates limbal vascular dilation, then new vessel growth
New vessels form along the epithelial BM or stroma

25
Q

Can the drop in cell proliferation be reversed?

A

Yes, with restoration of sufficient oxygen

26
Q

Does reperfusion of hypoxic retinal tissue promote or stop continued cell death? Explain (3).

A

Promote, probably due to excess metabolism, free radical promotion and ongoing effects of by-products of necrotic cells

27
Q

Consider absolute retinal ischaemia. List the two layers it generally affects and two factors that indicate it is irreversible.

A

Ganglion cell layer and nerve fibre layer
Oedema and pyknotic nuclei indicate irreversible damage

28
Q

Where does the majority of apoptosis occur following reperfusion in retinal ischaemia? What does this result in?

A

Inner nuclear layer and ganglion cell layer
Retinal thinning

29
Q

List the two sources of injury with ischaemia and the process it is caused by.

A

Lack of oxygen - necrosis
Perfusion - apoptosis