Aqueous Humor Drainage Pathway Flashcards
which two pathways can the aqueous humor exit the eye
either the trabecular route or the uveoscleral route
which route, trabecular or uveoscleral is pressure dependent
the trabecular route
what structures are part of the trabecular route
uveal and corneoscleral meshwork, juxtacanalicular connective tissue (JCT), endothelial lining of schlemms canal, collector channels, and aqueous veins
what drives the aqueous flow in the trabecular route
flows via bulk flow and is driven by a pressure gradient (active transport is not involved)
Does the amount of aqueous humor leaving the eye equal the amount being secreted?
yes
does the outflow resistance of the meshwork increase with age?
yes and in primary open angle glaucoma
how much does the uveoscleral route outflow account for
about 10-30%
what is another name for the Trabecular route
the conventional outflow route
how much outflow is the trabecular route responsible for
about 90%
where is the trabecular meshwork and Schlemms canal located
in the internal scleral sulcus
how many layers is the posterior trabecular meshwork
about 12-20 layers
how many layers are in the anterior portion of the trabecular meshwork
only 3-5 layers
because there are few layers at the apex of the trabecular meshwork, what is present here
a non-filtering portion
what may be present in the non-filtering portion of the trabecular meshwork
adult stem cells or progenitor cells, could replicate and repopulate the filtering portion after an injury
what are the 3 portions of the trabecular meshwork
the uveal, corneoscleral and JCT
what portion is the innermost portion of the trabecular meshwork
the uveal meshwork (faces the anterior chamber)
where is the corneoscleral meshwork
deep to the uveal meshwork
how many layers is the uveal meshwork
1-3 layers, originating from the anterior aspect of the ciliary body
how many layers is the corneoscleral meshwork
8-15 layers, originating in the scleral spur
why does the trabecular meshwork behave as a “self-cleaning” filter
the pores get progressively smaller from inner to outer and there is phagocytic activity
what is the juxtacanalicular connective tissue
an elastic-like fiber system, connects the inner wall endothelium with the trabecular lamellae
where does the fluid go after going through the JCT
into sclemms canal
what lines the inner walls of Schelmms canal
single layer of non-fenestrated endothelial cells
what is a unique feature of Schelmms canal
the presence of endothelial cells that experience a basal to apical direction pressure gradient
what are the pathways called in schlemms canal
giant vacuoles
what are the two distinct pores in the inner wall of the endothelium in schlemms canal
B pores and I pores
Where are the B (border) pores
between adjacent endothelial calls
where are the I pores found
on the basal and abluminal sides of the endothelial cells
after traveling circumferentially in the lumen of schlemms canal where does the aqueous exit
into collector channels and aqueous veins
how many collector channels are there
about 30-35 in the outer wall of Schlemms canal
where do the collector channels lead to
a venous plexi, then episcleral veins, then the greater venous circulation
what are the aqueous veins of Ascher
vessels that bypass the venous plexi and go to the episcleral veins
why can aqueous humor pass through the ciliary body near the iris root
because there isn’t any epithelium/ barrier between the anterior chamber and the clefts of the ciliary muscle
where does the aqueous humor flow in the uveoscleral route
between the ciliary muscle into a potential space between the ciliary body and the lamina fusca of the sclera (supraciliary space)
what might be a rate-limiting step for outflow of the uveoscleral route
the passage of aqueous humor through the ciliary fasicles
which pathway, trabecular or uveoscleral has been targeted with prostaglandin analogs to enhance aqueous humor outflow
uveoscleral
