Blood Supply- Arteries

Tunica Intima

Innermost vascular layer

Tunica Media

Middle vascular layer, contains smooth muscle

Tunica Adventitia

Outer connective tissue layer of blood vessels

Segmented Capillary Bed

Capillary bed with one inflow and one outflow; no redundancy

Overlapping Capillary Bed

Capillary bed with multiple inflows and outflows; redundancy and anastomoses

Fenestrated Endothelium

Endothelium with thin “windows”; highly permeable; found in choriocapillaris and ciliary processes

Continuous Endothelium

Endothelium with tight junctions; forms barriers; found in iris, retina; part of blood-retina barrier

Discontinuous Endothelium

Endothelium with pores that allow unregulated passage of fluid and cells

Neovascularization

Formation of new capillaries from existing vessels; response to oxygen demand or injury

Retinal Vessels Supply ______

Supply inner two-thirds of the retina

Uveal Vessels Supply _______

Supply outer one-third of retina (iris, ciliary body, choroid)

Internal Carotid Artery

Major artery supplying the orbit; gives rise to ophthalmic artery

Ophthalmic Artery

Main ocular artery; branch of internal carotid; enters through optic foramen, branches into central retinal artery, medial/lateral posterior ciliary arteries, muscular arteries, lacrimal artery, anterior/posterior ethmoid arteries, supraorbital artery, supratrochlear artery, dorsal nasal artery and medial palpebral artery

Central Retinal Artery

Branch of ophthalmic artery supplying inner two-thirds of retina; segmented end-arterial system, enters the optic nerve and supplies the pia mater and center of optic nerve, supplies inner 2/3 of retina (INL and GCL), lead to inferior and superior nasal/temporal artery and vein 

Posterior Ciliary Arteries

Branches of ophthalmic artery supplying uveal tract (choroid, iris, ciliary body), medial and lateral, each form LPCA and SPCAs

Long Posterior Ciliary Arteries

Two arteries (1 lateral 1 medial) running forward in choroid to ciliary body; form major arterial circle (continuous in iris)

Short Posterior Ciliary Arteries

10–20 arteries entering near optic nerve forming choroidal circulation (inner 1/3 of retina); create Circle of Zinn, supplies outer nerve head, continuous 

Circle of Zinn

Anastomotic ring of short posterior ciliary arteries around optic nerve head

Cilioretinal Artery

Optional artery supplying inner retina between optic nerve head and fovea

Muscular Arteries

Branches supplying extraocular muscles; give rise to anterior ciliary arteries and major perforating arteries

Anterior Ciliary Arteries

Branches from muscular arteries supplying conjunctiva, episclera, ciliary body, iris, form episcleral arteries and major perforating arteries

Episcleral Arteries

Branches of anterior ciliary arteries (7) entering conjunctiva forming episcleral circle near limbus, anterior = corneal arcades, posterior = superficial marginal plexus

Superficial Marginal Plexus

Network of conjunctival vessels branching from posterior episcleral arteries

Corneal Arcades

Anterior section of anterior ciliary arteries, arterioles supplying peripheral cornea without entering clear cornea

Major Perforating Arteries

Branches of anterior ciliary arteries entering sclera; form intramuscular circle and minor arterial circle

Intramuscular Circle

Major perforating arteries forming a vascular circle within ciliary muscle supplying ciliary body

Major Arterial Circle

Large arterial ring near root of iris from LPCA; supplies ciliary processes and iris

Minor Arterial Circle

Arterial ring at iris collarette supplying iris sphincter

Haller’s Layer

Outer choroid layer (near sclera) containing large vessels

Sattler’s Layer

Choroid layer closest to retina containing medium-sized vessels

Choriocapillaris

Inner choroid capillary bed supplying photoreceptors; fenestrated and highly permeable

Peripheral Retina Blood Flow, ability to compensate for arterial blockage

Venule-dominant; less able to compensate for arterial blockage

Central Retina Blood Flow

Arteriole-dominant; less able to compensate for venous blockage

Lacrimal Artery

Major branch of ophthalmic artery; supplies lacrimal gland, lateral rectus, upper brow, runs through orbit at the lacrimal fossa, leads to lateral palpebral artery

Lateral Palpebral Artery

Branch of lacrimal artery supplying eyelids

Anterior/Posterior Ethmoid Artery

Branch of ophthalmic artery supplying anterior/posterior ethmoid sinus and nasal mucosa

Supraorbital Artery

Terminal branch of ophthalmic artery; supplies upper eyelid, brow, forehead through supraorbital notch

Supratrochlear Artery

Terminal branch of ophthalmic artery; supplies medial eyebrow and forehead above trochlea

Dorsal Nasal Artery

Terminal branch of ophthalmic artery; supplies eyelid, lacrimal sac, nose, anastomoses with angular artery, runs below trochlea to exit orbit

Medial Palpebral Artery

Branch of ophthalmic or dorsal nasal artery; supplies eyelids; forms palpebral arcades

Angular Artery

Branch of facial artery (comes from external carotid); supplies palpebral arcades

Infraorbital Artery

Branch of maxillary artery (comes from external carotid); supplies inferior eyelid and cheeks, enters orbit via inferior orbital fissure, exits via infraorbital canal 

Palpebral Arcades

Arterial networks in eyelids formed by medial and lateral palpebral arteries

External Carotid Supply

Supplementary eyelid blood supply from facial and maxillary arteries

Cotton Wool Spot

Retinal infarct from CRA occlusion causing opaque area due to dead ganglion cells

End-Arterial System

Vascular system without collateral circulation; vulnerable to occlusion