9. Ciliary Body

Anterior chamber

Bordered anteriorly by the cornea and posteriorly by the iris and lens

Posterior chamber

Space between the posterior surface of the iris and the anterior surface of the vitreous

Parts of Ciliary Body

• Base

• Outer Side

• Inner Side

• Apex

Location of Ciliary Body

Behind the Iris and runs circumferential (triangular cross section)

Base of Ciliary Body

Anterior; at the limit of the iris root and scleral spur

Outer Side of Ciliary Body

Lies against the sclera

Inner Side of Ciliary Body

Faces aqueous humour (posterior chamber)

Apex of Ciliary Body:

Ora Serrata, which is also the transition zone between the ciliary body and the retina

Pars plicata = Corona ciliaris

Ciliary processes are the tissue crests
Function is aqueous humour production and assists in accomodation.

Pars plana = Orbicularis ciliaris

Flatter portion of ciliary body and extends from ora serrata to ciliary processes

Ora Serrata

Transition zone; termination of the retina

Supraciliaris = supraciliary lamina = anterior lamina fusca

• Outermost layer of the ciliary body which lies adjacent to the sclera

• Composed of pigmented ribbon like layers of loose connective tissue

• contains collagen type I, melanocytes, fibroblasts

• Runs diagonal to stroma and ciliary body

Function of Supraciliaris

• Serves as an intermediate

• Creates a potential space

• Fluid can drain here

• Expandable piece of tissue for muscle movement

Ciliary muscle layer

• Reticulum of smooth muscle with interweaving layer to layer

• Sphincter-like contraction of the ciliary muscle

• Fibers are subdivided into regions

  • Longitudinal fibers

  • Radial fibers

  • Circular fibers

Scleral spur

Located anterior to the ciliary body and composed of sclera; acts as an attachment for ciliary muscle and trabecular meshwork; Aids in aqueous humor drainage.

Longitudinal fibers

Run longitudinally; Origin = scleral spur; Insertion = “muscle stars” in suprachoroid

Radial fibers

Interdigitating V-shaped bundles; Origin = Scleral spur; Insertion = connective tissue near the posterior ciliary processes

Circular fibers

Lies nearest lens/posterior chamber; Origin = scleral spur; Insertion = connective tissue mid-ciliary processes; Sphincter action

Stroma of Ciliary Body

Continuous with Iris stroma and the Choroidal stroma
Composed of LCT, highly vascularized and capillaries are fenestrated
Contains melanocytes

Outer pigmented ciliary epithelium

Continuous with anterior epithelium of iris and pigmented epithelium of retina
Contains desmosomes, adherens junctions, gap junctions
The basement membrane attaches to the outer pigmented ciliary epithelium to the stroma

Inner non-pigmented ciliary epithelium

Continuous with posterior epithelium of iris and neural layers of retina
Contains desmosomes, interdigitations, gap junctions, and tight junctions
The internal limiting membrane is the basement membrane.
It is continuous with internal limiting membrane of the retina and posterior iris epithleium.

Which junction is found only in the inner unpigment epithelium and not in the outer pigmented epithelium?

Tight junctions

Ciliary Processes

Ciliary processes that arise from the ciliary body and are largely masses of small blood vessles.
Each consists of a central core of stroma covered by a double layer of epithelium: inner nonpigmented and outer pigmented epithelium and their associated basement membranes.

Characteristics of the capillaries in the Ciliary Processes

Capillaries in the ciliary processes are highly permeable (d/t fenestration, no endothelial cell overlap, no complete tight junctions)
Allows for easy movement of fluid and molecules

Ciliary Body Functions

Aqueous production; Produces some vitreal components; controls accommodation

Zonules

Composed of dense aggregates of microfilaments
Fibrillin is a critical glycoprotein (principle component)

Classification of main fibers

• Orbiculoposterior

• Orbiculoanterior

• Cilioposterior

• Cilioequatorial

Orbiculoposterior

Origin = ora serrata
Insertion = into posterior capsule (at ligament of Weiger)

Orbiculoanterior

Origin = CB pars plana
Insertion = Into the anterior lens capsule
Thickest and strongest zonules & attached to thickest part of lens capsule

Cilioposterior

Origin = CB valleys
Insertion = Into posterior lens capsule

Cilioequatorial

Origin = CB valleys
Insertion = Into equator of lens capsule

Classification of auxiliary fibers

1. Orbiculociliary: from pars plana to posterior ciliary process

2. Interciliary: from ciliary process to process

Function is to provide stability for primary zonules & hold ciliary body in place

Zonular Failure

Zonular tears or dehiscence
Lens destabilization or luxation (completely fallen out)

Ciliary Muscle

Action:
Contraction of muscle → eye focused for near
Relaxation of muscle → eye focused for distance

Innervation:
Parasympathetic stimulation activates muscle (contraction)
Sympathetic has an inhibiting effect; reduces activation