Function Of The Ciliary Body Flashcards
What is not a function of the ciliary body
Contains the minor arterial circle of the iris
-does contain the major circle
Order the structures appear on gonioscopy
Schwalbes line
TM
Sclera spur
Ciliary body
Are both posterior structures from the iris and the ciliary body pigmented?
No, iris is pigemented on the backside and the ciliary body is nonpigmented on the backside
Connected the cornea to the conjunctiva
Schwalbes line
Why is the ciliary muscle atypical for smooth muscle
Rapid contraction speed
Large size of motor neurons
Distance between the muscle and the motor neurons
Structure of the ciliary muscle cells resembles skeletal muscle
This is because we are constantly changing accommodation
Ciliary muscle in birds
It is skeletal muscle
Functions of the ciliary body
- aqueous production
- aqueous outflow
- accommodation
What is aqueous production important for
Supplies nutrients to lens and cornea BC they are avascular
What is aqueous outflow important for
Maintain IOP
Remove waste products
Production and secretion of aqueous humor
- Diffusion
- Ultrafiltration
- Active secretion (80-90% of production)
What is the most significant factor in aqueous production
Active secretion
What is the purpose of aqueous production
- nutrients to cornea and lens
- ascorbate cxn 20x higher in aqueous than in blood plasma
- free radical that is important to prevent oxidative damage
- low cxn of protein to prevent light scatter
- carries waste products from cornea and lens
- high cxn of lactate in aqueous, metabolic waste product of glycolysis of the lens and cornea
Ascorbate in aqueous
20x higher than in the blood
What is ascorbate in the aqueous important for
Prevent oxidative damage
Protein in the aqueous
Low levels to prevent light scatter
Lactate in the aqueous
High cxn of lactate which is a metabolic waste produce of glycolysis of the lens and cornea
How much aqueous is produced per minute
2.5 microliter
When is aqueous production higher
During the day, decreases 50% at night
Blood vessels and aqueous
Dilating and constricting blood vessels can influence aqueous blood vessels by increasing and decrease blood volume
Heh?
Size of zonular fibers
70-80nm in diamter
What are the zonular fibers
Elastic fibers
Stabilize the lens
Allows fluid to flow from posterior chamber to the vitreous chamber
Superficial attachment to the lens
When is acocmmodation completely lost by
Age 50
-some presbyopia read well due to pupil constriction and miosis
Tell me about accommodation
Contraction of the longitudinal fibers of the ciliary muscel pulls the choroid forward, the contraction of the circular fibers draws the ciliary body closer to the lens,decreased the diameter of the ring formed by the ciliary body. This releases tension on the zonular fibers and allows the lens capsule to adopt a more spherical shape. The lens thickens, and the anterior surface curvature increases. These changes result in an increase in refractivepower or accommodation
What is the lens contained in
An elastic envelope, the lens capsule
What is the lens capsule suspended by
Zonular fibers that arise from the dilatory epithelium and attach to the lens equator
Zonular fibers in far vision
While far vision is maintained the ciliary muscle is relaxed. Zonular fibers are pulling on the lens capsule
What happens to the zonular fibers when the ciliary muscle contracts?
The fibers slacken. The lens adopts a new shape with the anterior surface building forward and the lens becoming thicker with a decreased diamter thereby increasing the power of the lens
What does ACh bind
Ciliary muscle receptors (M)
Pilocarpine and ciliary muscle
Binds M receptors and can cause contraction
Which eyes will be less effected by dilating drops
Pigmented epithelium in the iris and ciliary body bind with this. Dark irides will therefore be less effected by dilating drops
Ciliary muscle can be temporarily paralyzed with _____
M antagonists like atropine, cyclopentolate, and tropicamide
Measuring accommodation
- rely on perception of clarity
- overestimate accommodative response
- acocmomdation and convergence stimulate miosis
- objective measurements can be obtained from autorefractoe and aberrometer
- push up test has an increase in letter size
- changes in illumination will after pupil diamter was well
What is reduce near vision from
Not a loss of ciliary body muscel function but from a thickened and stiff lens
Structural changes in aging eye that can affect accommodation
Thickening of tendons, reduced muscle mass and increase in connective tissue
Muscarinic receptors and aging
No cchange at all
Loss of the ability to accommodate
Presbyopia
-normal are-related change and the subject of significant research
Tendons and presbyopia
The tendon attaches the ciliary muscle to the scleral spur shows extensive age-related structural changes: it thickens with age and becomes surrounded by a dense layer of collagen thus losing its elasticity , restricts muscle movement
Ciliary muscel contractive power
Increases up until age that presbyopia manifests
- no change in zonular length with age
- aging ciliary muscle looks like young when relaxed
Ciliary strength and age
Gets stronger as you get older
Ciliary muscle contraction and aqueous outflow
Ciliary muscle contraction can change the configuration of the TM BC some of the longitudinal fibers are attached to TM sheets. This altered configuration can facilitate aqueous movement through the anterior chamber angle structures
Accommodation and IOP
Reduction
Iris sphincter muscle is derived from
Neural ectoderm
Ciliary muscle is derived from
Mesoderm
If breakdown of blood aqueous nbarrier occurs, cells and flare will be visible
Tyndall phenomenon
Factors of Tyndall phenomenon
- leukocyte
- usually whitish
- can form hypopyon
Trauma to head or injury such as whiplash can tear or break the iris. This can break the iris blood vessels entering from the major circle of the iris nad blood settles inferiroly
Hyphema
How to locate schwalbes line on gonio
Look where the two lines of light on the cornea come together and that is it
