BS - Uvea - Week 2 Flashcards
Where does the choroid begin?
Begins where the ciliary body ends.
What is the function of ciliary bodies?
Production of aqueous humour for nutrition.
What is the pars plicata?
It surrounds the ciliary processes, responsible for aqueous humour production.
What do the pars plicata attach to?
To the lens via zonules.
What is the pars plana, and what does it merge with? What is the border of mergence called?
Connects to the pars plicata inward, and merges with the retina. The border of pars plana and retina is called the ora serrata.
What is the favoured site for surgical injection to the eye, and why?
Ora serrata, as its least likely to be injured.
Describe the ciliary process epithelium.
It is double layered, in contact with the aqueous humour.
Is the inner epithelium of the ciliary processes pigmented?
No, only the outer epithelium is.
Where is the newly made aqueous humour released, and where does it go?
Released into the posterior chamber, and travels up, around the lens, and through the pupil, into the anterior chamber.
What is the inner layer of the epithelium of ciliary processes continuous with?
Neural retina.
What is the outer pigmented layer of the epithelium of ciliary processes continuous with?
RPE and iris.
What surrounds the outer epithelium of the ciliary processes?
The inner non-pigmented layer.
Inner surrounds outer.
Inner is non-pigmented, outer is pigmented.
What does the ciliary stroma border?
The ciliary muscle.
What covers the ciliary stroma?
Ciliary epithelium layers
Is the ciliary stroma vascular or avascular?
Richly vascularised.
Are pigmented cells present in the ciliary stroma?
Yes, melanocytes.
Are fibroblasts present in the ciliary stroma?
Yes.
What immune cells can eb found in the ciliary stroma?
Mast cells, macrophages, and lymphocytes.
Name the three ciliary muscles beginning with the most superficial. Which has the main bulk?
Longitudinal fibres - forms main bulk
Oblique fibres
Circular fibres
Which of the ciliary muscles runs parallel with the sclera?
Longitudinal fibres
During accommodation, which surface of the lens changes more, anterior or posterior?
Anterior.
What happens to the lens with age?
Thickens
What happens when you accommodate?
Ciliary muscles contract, which loosen the zonules, and allow the lens to increase in curvature.
When relaxed, zonules tighten, and pull the lens.
Do ciliary muscles receive mainly sympathetic or parasympathetic innervation?
Parasympathetic system.
Sympathetic - 1-2%
Describe the parasympathetic innervation to the ciliary muscles, including the receptor, nerve pathway, and cranial nerve if applicable.
Receptor - muscurinic receptors To - the midbrain Via - ciliary ganglion Nerve - short posterior ciliary nerve Cranial nerve III, inferior division
Describe the sympathetic innervation to the ciliary muscles, including the receptor, nerve pathway, and cranial nerve if applicable.
Receptor - β2 adrenergic receptors To - the midbrain Via - superior cervical ganglion Nerve - long ciliary nerve Cranial nerve III, inferior division
What vessels supply blood to the ciliary bodies?
Long posterior ciliary arteries
Anterior ciliary arteries
How do anterior ciliary arteries reach the ciliary bodies? What about the long posterior ciliary arteries?
They travel via the extraoccular muscles
Long posterior ciliary arteries travel between the sclera and the choroid.
What do the anterior ciliary arteries and long posterior ciliary arteries form?
Major arterial circle.
Describe the choroid, its colour, and its four main layers.
Thin inner brown lining of the sclera Suprachoroid Stroma Choriocapillaris Bruch's membrane
Where does the choroid cover?
From the optic nerve, to the ciliary bodies.
What is another name for the suprachoroid, and what kind of tissue is it? What arteries and cells are found here?
Lamina fusca
Is loose connective tissue
Long and short posterior ciliary arteries move into this space
Melanocytes are found here
Describe the two layers of the choroid stroma. Arteries (P/A CA) run here, describe what happens to arterial diameters.
Haller’s layer - outer layer, with larger diameter arteries
Sattler’s layer - inner layer, middle/medium-sized arteriolar branches
Describe the choriocapillaris. Where is its greatest density?
Large fenestrated capillary bed. Greatest density in the macular region.
What layerchoroid layer is closest to the retina?
Choriocapillaris
Where are vortex veins found, and how many does each eye have?
Found in the choriocapillaris, 4 per eye, one for each quadrant.
Where can bruch’s membrane be found?
Between the choroid and RPE.
Describe the 5 layers of bruchs membrane.
RPE basement membrane Inner layer of collagen Meshwork of eastic fibres Outer layer of collagen Endothelial basement membrane
Where does drusen develop, and what is it a precursor to?
Develops between the RPE basement membrane and the inner collagen layer.
Precursor to AMD.
How does Bruchs membrane appear with age?
Takes on a patchy appearance with age., and thickens.
What happens to choroidal vessels with age?
Arteriosclerosis >60 years.
What separates the anterior and posterior chambers of the eye?
Iris
Where does the iris insert into?
Ciliary body - iris root
What is the free edge of the iris called?
Pupillary margin
What are the embryological origins of the iris?
Stroma - mesoderm
Muscles, epithelium - ectoderm
Is the iris pigmented anteriorly or posteriorly?
Posteriorly.
Describe crypts of Fuch, and their function.
Openings on the anterior surface of the iris, allowing deeper structures to be bathed in aqueous humour.
What is the pupillary ruff?
Continuation of the posterior pigmented layer over the edge of the pupil anteriorly.
What are collarettes?
Divides the pupil into zones.
What are contraction furrows?
Ridges in the periphery that deepen as the pupil dilates.
Describe the posterior surface of the iris surface. What structure is found close to the pupillary zone?
A series of radial contraction folds are found close to the pupillary zone called Schwalbes folds. To the periphery of this are the circular contraction folds.
Does the anterior border of the iris have an epithelium?
No
Is the stroma of the iris vascularised?
Yes
Describe the pigmented epithelium of the iris.
Composed of 2 layers of cells, densely packed with melanin.
Where are sphincter pupillae found, what kind of muscle is it, and what nerve innervates it?
Found in the pupillary zone, is a smooth muscle, and receives parasympathetic supply from SPCN CNIII.
Define meiosis.
Pupillary constriction.
Define mydriasis.
Pupillary dilation.
Where are dilator pupillae found, what kind of muscle is it, and what nerve innervates it?
Found in the periphery of the iris, and gradually diminishes until the mid-portion od sphincter muscles.
Innervated by sympathetic supply via LPCN.
What does eye colour depend on?
Amount of melanin in the epithelium.
What colour are infant eyes?
Born light, gradually darkens with melanin deposition.
How is melanin found in the iris?
In bundles of melanosomes.
What kind of receptors and neurotransmitters are used for iris innervation?
Acetylcholine neurotransmitter
Muscurinic or nicotinic receptors
The nerve pathway for sympathetic innervation to the iris follows what?
The carotid plexus.
Where does sensory innervation to the iris originate from? Name each nerve branch.
Ophthalmic branch of the trigeminal nerve. Continues as nasociliary nerve.
Follows the long ciliary nerve.
Consider dilating drops, what chemicals would be needed to target sympathetic/parasympathetic innervation? Mention if it increases or decreases activity.
Increased sympathetic activity - Sympathomimetic
Decreased parasympathetic activity - antimuscurinics
Consider constricting drops. What chemicals would be needed to target sympathetic/parasympathetic innervation? Mention if it increases or decreases activity.
Increased parasympathetic activity - muscurinic agonists
How many arterial circles are formed?
One major to the periphery, one minor closer to the centre.
