ANATOMY - Ciliary Body

Question 1

What are the layers of the ciliary body? (5)

Answer 1

1. Internal Limiting Membrane (AC - inside)
2. Non Pigmented Inner Epithelium
3. Pigmented outer epithelium
4. Stroma of Ciliary body
5. Supraciliary Lamina (sclera - outside)

Question 2

What is contained in the stroma of the ciliary body (3)

Answer 2

1) Connective tissue and Collagen
2) Ciliaris Muscles

Question 3

What are the main structural features of the ciliaris muscle?

What type of muscle is it?

What are the types of muscle fibres contained within it?

Answer 3

Non striated involuntary muscle triangular in shape
1. Longitudinal muscle fibres - attachment to scleral spur and assist drainage of aqueous
2. Circular muscle fibres - accomodation
3. Radial muscle fibres

Question 4

What is the action of the ciliary muscle in accomodation?

Answer 4

Contraction of ciliary muscle towards lens –> slackening/loosening of zonules —> increase in anterior curvature of the lens –> increased lens power –> accomodation

Question 5

What is the nerve supply of the ciliary muscle?

Answer 5

Parasympathetic innovation from 3rd nerve postganglionnic fibres

Ciliary ganglion –> short ciliary nerve to supply the ciliary muscle and sphincter pupillae

Question 6

What vessel is contained in the stroma of the ciliary body?

Answer 6

Major arterial circle formed by long posterior ciliary arteries and anterior ciliary arteries

Question 7

What is the continuation of the pigmented epithelium of ciliary body (outer epithelium towards sclera)

Answer 7

Anteriorly continuation anterior epithelium of iris
Posterior continuation of RPE of retina

Question 8

What is the continuation of the non pigmented inner epithelium of the ciliary body?

Answer 8

Continues anteriorly with posterior pigmented epithelium of iris

Continues posteriorly with the neurosensory retina

Question 9

What is the length of the ciliary process ? How many are there?
Which part of the ciliary body has this

Answer 9

finger like projections 2mm in length, about 70-80 in number in the pars plicata

Question 10

What is the ultrastructure of the ciliary process?

Answer 10

Epithelium contains fenestrations which facilitates ultrafiltration of water, ions and large proteins in to the adjacent stroma

High oncotic pressure in ciliary process stroma –> aqueous humor secretion

Question 11

What type of epithelium is present in the ciliary body/ciliary process? Where is it from embryologically?

Answer 11

1. Bilayered epithelium - pigmented outer and non-pigmented inner epithelium
2. Neuroectodermal origin - anterior end of the optic cup

Question 12

What is the difference between pigmented outer epithelium and non-pigmented inner epithelium of the ciliary body (3)

Answer 12

1. Outer pigmented - low cuboidal cells
   Inner non-pigmented - columnar cells

2.
Outer pigmented - melanin granules separated from stroma by atypical basement membrane (continuation of Bruch’s)

Inner non-pigmented - mitochondria and endoplasmic reticulum separated with typical basement membrane with tight junctions on apical surfaces

3. Separated by low resistance gap junctions to faciliate ion transport between epithelial layers crucial for aqueous humor secretion
   Each layer connected to each other by tight junctions which forms blood-aqueous barrier

Question 13

What are the structures that form the blood aqueous barrier? (4)

Answer 13

1. tight junctions between cells of inner non-pigmented inner epithelium of ciliary body
2. tight junctions between outer pigmented epithelium of ciliary body
3. Non-fenestrated iris vessels
4. posterior iris epithelium