Structure and Function of the Retinal Vasculature

Question 1

What are the three layers of the Artery?

Answer 1

Outer layer = Tunica Adventitia
Middle layer = Tunica media
Inner layer = Tunica intima

Question 2

What is the Adventitia layer of artery?

Answer 2

It consists of fibrous tissue through which the vessel runs
- Merges with the loss connective tissue through which the vessel runs
- Helps to anchor the artery in place when exposed to cardiac pressure

Question 3

What is the elastic Tunica media layer of the Artery?

Answer 3

This differs between the elastic and muscular arteries
- In the elastic arteries the tunica media is very thick concentric sheets of elastin supported by collagen
- Smooth muscle fibres run between the sheets

Question 4

What is the muscular tunic media layer artery?

Answer 4

This is thinner
- Mostly smooth muscle fibres arranged concentrically with small numbers of elastic fibres in between
- Most elastic fibres concentrated as sheets between the intima and media and adventitia and media elastic lamina

Question 5

What is the tunica media layer of the artery?

Answer 5

The innermost layer of the artery
- A single layer of endothelial cells facing the lumen
- Underlying the endothelial cells is a thin collagenous and elastic matrix

Question 6

What is the role of endothelium cell blood vessels?

Answer 6

• Influence blood flow
• Act as a selective permeability barrier
• Regulate vessel homeostasis
• Mediate leukocyte adhesion and migration

Question 7

What is the ocular blood supply?

Answer 7

-Blood exits the left ventricle of the heart via the aorta
-Branches into the right and left common carotid artery
-Branches into the right and left internal carotid artery
- Enters the orbit via right and left ophthalmic artery

Question 8

How is blood supplied to the posterior choroid?

Answer 8

It is supplied by approx 20 short posterior ciliary arteries

Question 9

How is blood supplied to the anterior choroid?

Answer 9

Supplied by the long posterior ciliary arteries and recurrent branches of the anterior ciliary arteries

Question 10

What are Choriocapillaris?

Answer 10

A dense bed of highly fenestrated capillaries, deep to Bruch’s membrane, that supplies the retina
- It supplied by arteries in the underlying vascular layer

Question 11

What is vasculogenesis?

Answer 11

This is the de novo formation of a blood vessel from angioblasts
- Formation of the heart and primitive vascular plexus in an embryo

Question 12

What angiogenesis?

Answer 12

This is the expansion of the vasculature from existing vessels
- Remodelling and expansion of existing vessels to create the mature circulatory system

Question 13

What is neovascularisation?

Answer 13

Newly established blood networks that develop in response to stimuli
- Retinal angiogenesis ceases at birth
- Neovascular networks do not follow the usual branching patterns because the molecular cues that initiate neovascularisation are local and not well controlled

Question 14

What is Arteriovenous shunt?

Answer 14

This provides the capillary bed bypass between an arteriole and a venule
- It is a largely normal vascular structure

Question 15

What is a dot haemorrhage?

Answer 15

• This is a rupture of deep capillaries
• Diabetes

Question 16

What is a flame haemorrhage?

Answer 16

• Rupture of superficial precapillary arterioles or small veins
• Systemic hypertension, leukemia, severe anemia, retinal vein occlusion and trauma.

Question 17

What is a boat haemorrhage?

Answer 17

• Rupture of large superficial retinal veins into the pre-retinal space
• Sudden increase in intracranial pressure, anaemia, trauma

Question 18

What is a submacular haemorrhage?

Answer 18

• Rupture of choroidal vessels under the fovea
• AMD

Question 19

What is a vitreous haemorrhage?

Answer 19

• Rupture of superficial retinal vessels or vessels on a fibrovascular stalk extending into the vitreous
• Proliferative diabetic retinopathy, hypertension and trauma