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OD1 Semester 2 - Integrated Ophthalmic Sciences and Preclinical Optometry > Blood ocular barrier - Week 3 > Flashcards

Blood ocular barrier - Week 3 Flashcards

1
Q

What 3 layers of tissue make up the walls of blood vessels?

A
  1. Tunica intima - single layer of flattened squamous endothelial cells + underlying conn. tissue
  2. Tunica media - circumferential SMCs + external elastic lamina
  3. Tunica adventitia - fibroelastic tissue
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2
Q

What cells line the blood vessel lumen?

A

Endothelial cells

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3
Q

How are endothelial cells connected

A

via tight junctions

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4
Q

What is the effect of nicotine and other toxic substances on endothelial cells?

A

they break the tight junctions causing leaky blood vessels

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5
Q

Describe the role of pinocytotic vesicles.

A
  • allows passage of fluid across cells from the blood
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6
Q

Where are pinocytotic vesicles found?

A

In Endothelial cells

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7
Q

How are endothelial cells involved with blood vessel autoregulation?

A

They release peptides for vasoconstriction or vasodilation

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8
Q

How does noradrenaline affect blood vessels?

A

Causes them to constrict, lowering size of blood vessel lumen (is sympathetic)

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9
Q

What is the general term that describes the layers of tissue forming the walls of a blood vessel?

A

Tunics

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10
Q

Define Elastic Artery, what does it contain? And what does this achieve?

A

An artery with a large number of collagen and elastin filaments in the tunica media, giving it the ability to stretch with each pulse

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11
Q

Describe the location of elastic arteries (compared to other arteries)

A

They are the arteries closest to the heart

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12
Q

List all elastic arteries that are close to the heart

A
  • aorta + branches originating from aortic arch (common carotid, subclavian)
  • common iliac arteries
  • pulmonary trunk
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13
Q

Describe the general structure of elastic arteries, what do their tunica media consist of? How is their blood supply?

A
  • their tunica media consists of many fenestrated lamallae of elastin
  • extensive vasa vasorum (network of small blood vessels supplying large blood vessels)

That’s right, elastic arteries are so THICC, that they need their own blood supply

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14
Q

What is another name for muscular arteries?

A

Distributing arteries

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15
Q

What are Muscular arteries? Where do they draw blood from? Where do they branch?

A

medium sized arteries that draw blood from elastic arteries and branch into “resistance vessels” incl. small arteries and arterioles

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16
Q

List the branches of the ophthalmic artery

A
  1. Central retinal artery
  2. Lacrimal artery
  3. Posterior ciliary arteries (long posterior and short)
  4. Muscle branches
  5. Supraorbital artery
  6. Ethmoidal arteries
  7. Medial palpebral arteries
  8. Terminal branches
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17
Q

Where does the ophthalmic artery arise from?

A

It is the first branch of the Internal carotid artery distal to the cavernous sinus

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18
Q

What are the distinguishing features of muscular arteries?

A
  • internal elastic lamina = prominent + undulates (moves with smooth wave-like motion)
  • THICC tunica media composed of mostly SMCs (40 layers)
  • sparse vasa vasorum in tunica adventitia
19
Q

Define vasa vasorum

A

network of small blood vessels supplying large blood vessels

20
Q

Describe sympathetic blood vessel fibres involved with vasoconstriction

A
  • they are unmyelinated and post-ganglionic
21
Q

How large are arterioles

A
  • less than 0.1mm diagmeter
22
Q

In relation to the size of the lumen, how wide are the walls of arterioles?

A

equal to size of lumen

23
Q

Describe the general features of arterioles , in terms of their tunic content

A
  • tunica intima: no internal elastic lamina, except in larger arterioles
  • tunica media: 1-3 SMCs
  • no external elastic lamina
  • tunica adventitia: very little
24
Q

Where do capillaries arise?

A

From the terminal end of an arteriole

25
Q

Define capillaries

A

basically a single layer of endothelial cells

26
Q

How do pericytes interact with capillaries

A

They provide much needed structural support to the capillaries

27
Q

What do capillaries form a network between?

A

arteriole and venule

28
Q

Describe the general features of capillaries

A
  • single layer of squamous endothelial cells
  • only tunica intima (with no IEL)
  • one endothelial cell forms the “tube” - usually 10cm
  • pericytes are located on the outside of capillaries + venules
29
Q

List the 3 types of capillaries. What is the key difference between them?

A
  1. Continuous
  2. Fenestrated (2 types)
  3. Non-continuous/Sinusoidal

Key difference = endo. walls. Fenestrated has holes in them, continuous has no holes.

30
Q

Describe the features of fenestrated capillaries

A
  • thin wals
  • fenestrations covered by basal lamina
  • large fluid movement
  • found in choroid and ciliary body
31
Q

Describe the features of continuous capilaries

A
  • have endothelial cell tight junctions
  • big molecules: active transport
  • small molecules: diffusion
  • found in retina and iris
32
Q

Describe the features of dis-continuous capillaries

A
  • large and tortuous
  • fenestrated incomplete basal lamina
  • not found in eye (are found elsewhere in body)
33
Q

What is the role of veins?

A

transport blood back to the heart

34
Q

What are more numerous, veins or arteries?

A

Veins outnumber arteries

35
Q

T/F Veins have small luminal diameters

A

False. Veins have large luminal diameters because they carry 70% of total blood

36
Q

Describe the general structure of veins

A
  • thin walls (thinner than arteries)
  • layering within walls is indistinct
  • can be small, medium and large veins
  • contain up to 3 tunics like arteries (muscular + elastic layers are not well developed)
37
Q

Which has thinner walls, veins or arteries? What does this suggest?

A

Veins have thinner walls. This means the veins more easily burst open with higher IOP (still way higher than normal)

38
Q

Explain how veins react to the following IOP levels: 35mmHg, 50mmHg

A

35: veins try to widen
50: veins can’t widen anymore, they then burst open

39
Q

What happens when IOP is greater than MAP

A

you start to lost perfusion pressure

40
Q

Where does blood from capillaries go to?

A

is discharged into post-capillary venules

41
Q

What size are venules in diameter?

A

They are small, ~0.02-0.2mm in diameter

42
Q

Are venule walls similar to capillaries?

A

yes

43
Q

Describe venule walls

A

Thin endothelium surrounded by reticular fibres + pericytes

44
Q

In venules, what happens to pericytes as diameter increases

A

They are replaced by SMCs (smooth muscle cells)

OD1 Semester 2 - Integrated Ophthalmic Sciences and Preclinical Optometry (49 decks)

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