Accommodation Flashcards
Name the structures involved in accommodation
- ciliary body
- choroid
- iris
- anterior and posterior zonules
- crystalline lens/lens capsule
What type of muscle is the ciliary muscle?
Smooth muscle
Explain the role of parasympathetic and sympathetic on the ciliary muscle
- para has primary control and does contraction
- sym has little control but helps with relaxation.
-it has both because it acts as its own antagonist
What is the origin of the longitudinal muscle bundle? Where do the longitudinal fibers extend to?
- epichoroidal stars that attach the muscle to the outer surface of the choroid and act as a posterior anchoring point.
- then attach to the scleral spur and extend into the trabecular mesh work
Which muscle bundle has the greatest contribution to changing the lens shape? Why?
-circular/angular bundle because as the muscles contract, there is a gradual transition from longitudinal and radial fibers into angular fibers
What is the primary function of the ciliary body?
-to move the anterior choroid forward and release resting tension of the zonular fibers
Which muscle fibers contract during accommodation?
All three
Why would we use pilocarpine to treat glaucoma?
- it simulates parasympathetic innervation and accommodation, causing contraction
- this moves the scleral spur posteriorly and opens flow channels to enhance flow across the TW.
- it INCREASES effective filtration area
What would happen with the application of atropine?
- it relaxes the ciliary muscle
- closes flow channels and decreases effective filtration area
What kind of fibers are the zonules?
Elastin based fibers
What is the difference between NPCE at the tips of the ciliary processes and NPCE in the valleys?
- NPCE at the tips are modified to secrete aqueous humor
- NPCE in valleys is modified to secrete zonules and anchor them
What is the primary function of the zonules?
Stabilize the lens
Where do the anterior zonules attach?
At the anterior capsule surface (anterior group), equator (equatorial group), and posterior capsule (posterior group)
Where do the posterior zonules attach?
- attaches to the inner limiting membrane covering the NPCE near the ora serrate
- then enter valleys between ciliary processes and insert into NPCE either in the valleys or walls of the ciliary processes.
What is the function of the posterior zonules?
To pull the ciliary muscle back to its unaccommodative state position after accommodation has stopped
