Aqueous Humor Drainage Pathway

Question 1

which two pathways can the aqueous humor exit the eye

Answer 1

either the trabecular route or the uveoscleral route

Question 2

which route, trabecular or uveoscleral is pressure dependent

Answer 2

the trabecular route

Question 3

what structures are part of the trabecular route

Answer 3

uveal and corneoscleral meshwork, juxtacanalicular connective tissue (JCT), endothelial lining of schlemms canal, collector channels, and aqueous veins

Question 4

what drives the aqueous flow in the trabecular route

Answer 4

flows via bulk flow and is driven by a pressure gradient (active transport is not involved)

Question 5

Does the amount of aqueous humor leaving the eye equal the amount being secreted?

Answer 5

yes

Question 6

does the outflow resistance of the meshwork increase with age?

Answer 6

yes and in primary open angle glaucoma

Question 7

how much does the uveoscleral route outflow account for

Answer 7

about 10-30%

Question 8

what is another name for the Trabecular route

Answer 8

the conventional outflow route

Question 9

how much outflow is the trabecular route responsible for

Answer 9

about 90%

Question 10

where is the trabecular meshwork and Schlemms canal located

Answer 10

in the internal scleral sulcus

Question 11

how many layers is the posterior trabecular meshwork

Answer 11

about 12-20 layers

Question 12

how many layers are in the anterior portion of the trabecular meshwork

Answer 12

only 3-5 layers

Question 13

because there are few layers at the apex of the trabecular meshwork, what is present here

Answer 13

a non-filtering portion

Question 14

what may be present in the non-filtering portion of the trabecular meshwork

Answer 14

adult stem cells or progenitor cells, could replicate and repopulate the filtering portion after an injury

Question 15

what are the 3 portions of the trabecular meshwork

Answer 15

the uveal, corneoscleral and JCT

Question 16

what portion is the innermost portion of the trabecular meshwork

Answer 16

the uveal meshwork (faces the anterior chamber)

Question 17

where is the corneoscleral meshwork

Answer 17

deep to the uveal meshwork

Question 18

how many layers is the uveal meshwork

Answer 18

1-3 layers, originating from the anterior aspect of the ciliary body

Question 19

how many layers is the corneoscleral meshwork

Answer 19

8-15 layers, originating in the scleral spur

Question 20

why does the trabecular meshwork behave as a “self-cleaning” filter

Answer 20

the pores get progressively smaller from inner to outer and there is phagocytic activity

Question 21

what is the juxtacanalicular connective tissue

Answer 21

an elastic-like fiber system, connects the inner wall endothelium with the trabecular lamellae

Question 22

where does the fluid go after going through the JCT

Answer 22

into sclemms canal

Question 23

what lines the inner walls of Schelmms canal

Answer 23

single layer of non-fenestrated endothelial cells

Question 24

what is a unique feature of Schelmms canal

Answer 24

the presence of endothelial cells that experience a basal to apical direction pressure gradient

Question 25

what are the pathways called in schlemms canal

Answer 25

giant vacuoles

Question 26

what are the two distinct pores in the inner wall of the endothelium in schlemms canal

Answer 26

B pores and I pores

Question 27

Where are the B (border) pores

Answer 27

between adjacent endothelial calls

Question 28

where are the I pores found

Answer 28

on the basal and abluminal sides of the endothelial cells

Question 29

after traveling circumferentially in the lumen of schlemms canal where does the aqueous exit

Answer 29

into collector channels and aqueous veins

Question 30

how many collector channels are there

Answer 30

about 30-35 in the outer wall of Schlemms canal

Question 31

where do the collector channels lead to

Answer 31

a venous plexi, then episcleral veins, then the greater venous circulation

Question 32

what are the aqueous veins of Ascher

Answer 32

vessels that bypass the venous plexi and go to the episcleral veins

Question 33

why can aqueous humor pass through the ciliary body near the iris root

Answer 33

because there isn’t any epithelium/ barrier between the anterior chamber and the clefts of the ciliary muscle

Question 34

where does the aqueous humor flow in the uveoscleral route

Answer 34

between the ciliary muscle into a potential space between the ciliary body and the lamina fusca of the sclera (supraciliary space)

Question 35

what might be a rate-limiting step for outflow of the uveoscleral route

Answer 35

the passage of aqueous humor through the ciliary fasicles

Question 36

which pathway, trabecular or uveoscleral has been targeted with prostaglandin analogs to enhance aqueous humor outflow

Answer 36

uveoscleral