16 Questions
What are the two main branches of the common carotid artery, and what structures do they supply?
The two main branches of the common carotid artery are the internal carotid artery, which supplies structures internal to the skull, and the external carotid artery, which supplies structures external to the skull, including a small portion of the ocular adnexa.
What is the significance of the Circle of Willis in maintaining blood flow to the brain?
The Circle of Willis is a cerebral arterial circle that provides equal blood pressure and alternative routes for blood flow in the event of a clot or blockage, ensuring continued blood supply to the brain.
What are the main branches of the ophthalmic artery, and what structures do they supply?
The main branches of the ophthalmic artery include the central retinal artery, lacrimal artery, posterior ciliary arteries, and muscular arteries, which supply the retina, lacrimal gland, and ocular adnexa.
What is the function of the Blood-Retina Barrier, and how is it maintained?
The Blood-Retina Barrier is a specialized barrier that prevents the passage of certain substances from the blood into the retina, and is maintained by tight junctions between the retinal pigment epithelium and endothelial cells of retinal capillaries.
What are the two main types of branches that the central retinal artery subdivides into, and what is the significance of this branching pattern?
The central retinal artery subdivides into superior and inferior branches, and then further into nasal and temporal branches, which is significant for providing a uniform blood supply to the retina.
What is the effect of aging on the retinal circulation, and how does this lead to changes in the Blood-Retina Barrier?
Aging leads to changes in the retinal circulation similar to those found elsewhere in the body, such as arteriosclerosis, which can cause loss of cells at the capillaries, including endothelial cells, and disrupt the Blood-Retina Barrier.
What is the age-related change in retinal microcirculatory flow, leading to tissue perfusion?
Diminished retinal microcirculatory flow
What is the predictor of age-related macular degeneration (AMD), especially its atrophic form (dry AMD)?
Large drusen
What is the main artery that supplies the choroid?
Posterior ciliary arteries
What is the site of anastomosis between the long posterior ciliary arteries and anterior ciliary arteries?
Major circle of iris
What is the function of the supratrochlear artery?
Supplies the skin of the forehead and scalp, and the forehead muscles
What is the blood supply to the extraocular muscles?
Muscular arteries
What is the function of the lacrimal artery?
Supplies the lacrimal gland, conjunctiva, and lids
What is the characteristic of the veins draining the globe and orbit?
No valves
What is the age-related change in the pericyte basement membrane?
Thickening
What is the function of the central retinal artery?
Supplies the retina
Study Notes
Blood Supply to the Eye and Adnexa
- The blood supply to the head and neck originates from the arch of aorta, which divides into brachiocephalic trunk, left common carotid, and right subclavian and right common carotid arteries.
- The common carotid arteries further divide into internal carotid and external carotid arteries.
- The external carotid artery has 9 branches, including branches that supply the ocular adnexa.
Ophthalmic Artery
- The ophthalmic artery arises from the internal carotid artery and has several branches:
- Central retinal artery
- Lacrimal artery
- Posterior ciliary arteries (short and long)
- Muscular arteries
- Ethmoid arteries
- Supraorbital artery
- Medial palpebral arteries
- The central retinal artery pierces the optic nerve and divides into superior and inferior branches, which further subdivide into nasal and temporal branches.
- The central retinal artery provides blood supply to the optic nerve and pia matter.
Retinal Circulation
- The retinal circulation has a blood-retina barrier formed by tight junctions between RPE cells and endothelial cells of retinal capillaries.
- Autoregulation maintains constant blood flow despite changes in intraocular pressure and systemic blood pressure.
- Age-related changes in retinal circulation include:
- Loss of cells at capillaries
- Thickening of pericyte basement membrane
- Narrowing of vascular lumens
- Decreased capillary number in the macula
- Decreased blood flow in people over 50 years old
Choroid and Bruch's Membrane
- The choroid receives blood supply from the posterior ciliary arteries.
- Age-related changes in Bruch's membrane include thickening, decreased permeability, and accumulation of extracellular debris (drusen).
- Drusen are a predictor of age-related macular degeneration (AMD).
Extraocular Muscles
- The extraocular muscles receive blood supply from muscular arteries that branch from the arteries supplying the recti muscles.
- The lateral-superior artery supplies the lateral rectus, superior rectus, superior oblique, and levator muscle.
- The medial-inferior artery supplies the medial rectus, inferior rectus, and inferior oblique.
Lacrimal Gland and Eyelids
- The lacrimal gland receives blood supply from the lacrimal artery, which also supplies the lateral rectus muscle and sends branches to the conjunctiva and eyelids.
- The medial palpebral arteries supply the eyelids and anastomose with branches from the lacrimal artery to form palpebral arcades.
- The dorsonasal artery supplies the lacrimal sac and anastomoses with the angular artery from the external carotid.
This quiz covers the anatomy and functions of the blood supply to the eye and its surrounding structures, including the lacrimal apparatus, conjunctiva, eyelids, and more.
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