EVS Week 10 - Vasculature

what part of the eye do the ciliary arteries supply?

the uveal tract (iris, ciliary body, choroid)

what do the short posterior ciliary arteries supply?

• posterior choroid

• optic nerve

• optic nerve head

what do the long posterior ciliary arteries supply?

• choroid

• ciliary body

• iris

what do the anterior ciliary arteries supply?

• iris

• ciliary body

• anterior choroid

what are the 3 general functions of blood?

1. Transportation — transport O2 from lungs to body, CO2 from cells to lungs, provide nutrients, heat and waste products away from cells

2. regulation — pH and heat absorption/coolant properties

3. protection — white blood cells and plasma proteins; clotting mechanism to stop blood loss

how do normal capillaries facilitate passive diffusion?

• they have a single layer of endothelial cells

how does the blood-brain-barrier maintain a stable environment?

• it has tight junctions in the vessel wall between endothelial cells to prevent toxins entering the brain

• nutrient and waste products are exchanged through active transport in the endothelium

what makes up the internal carotid artery system?

• internal carotid artery

• anterior cerebral arteries

• middle cerebral arteries

what parts of the brain does the anterior cerebral artery supply?

• medial portion of the frontal lobes, parietal lobes and temporal lobes

what parts of the brain does the middle cerebral artery supply?

• supplies the largest area of the cortex

• supplies the lateral portion of the frontal lobes, parietal lobes, superior portion of temporal lobes

where does the internal carotid artery travel?

it travels through the cavernous sinus: area where CN 3-6 pass

which arteries supply both sides of the cerebral hemispheres?

posterior cerebral arteries

what are the 3 layers that make up arteries and veins?

1. tunica externa — outermost layer

2. tunica media — middle layer

3. tunica intima — innermost layer

where does the central retinal artery run?

• it runs through the centre of the optic nerve

• exits at the optic nerve head

what are the 2 branches of the central retinal artery?

• the superior and inferior retinal arteries

  • these each divide into the nasal and temporal retinal branches

where do the retinal arteries lie and what do they supply?

• they lie in the inner layers of the retina

• supply as far as the inner nuclear layer of the retina

where does deoxygenated blood from the eye drain?

• the vortex veins and central retinal vein

what veins form when the vortex veins and central retinal vein join?

• the form the superior and inferior ophthalmic veins

where do the superior and inferior ophthalmic veins drain?

• the cavernous sinus

what are the branches of the ophthalmic artery?

mnemonic: DR MCLESSI
D - dorsal nasal artery
R - (central) retinal artery
M - (extra-ocular) muscular branches
C - ciliary arteries
L - lacrimal artery
E - ethmoidal arteries
S - supra-orbital artery
S - supratrochlear artery
I - internal (medial) palpebral arteries

where does the ophthalmic artery run and emerge?

• runs beneath the optic nerve

• emerges through the optic foramen laterally before branching into arteries

how do the ciliary arteries arise?

internal carotid artery —> ophthalmic artery —> posterior ciliary arteries — travels along the sides of the optic nerve

how is the major arterial circle formed?

• formed by the 2 branches of the long posterior ciliary artery and 7 branches of the anterior ciliary artery

what is the major arterial circle?

it is an outer ring on the iris

what is the minor arterial circle?

• the long posterior ciliary artery and anterior ciliary artery join to form the minor arterial circle

why is the minor arterial circle important?

• it allows the iris to dilate and constrict without damaging the vessels

what is the circle of willis?

• it is a ring of arteries at the base of the brain that provides a collateral blood supply

how is the circle of willis formed?

• it is formed by the anterior and posterior cerebral arteries, the internal carotid artery and the basilar artery

what structures does the circle of willis wrap around?

• the optic chiasm and hypothalamus

what is the importance of the circle of willis?

• it ensures continued circulation if one of the major arteries becomes blocked (vertebral or internal carotid)

• it also ensures equal nutrition to the brain

what would happen if there was a posterior cerebral artery blockage?

• there would be field loss e.g. hemianopia as the occipital lobe is affected

what areas do the posterior cerebral artery supply?

• occipital lobe

• inferior temporal lobe

• supply both sides of the cerebral hemispheres