Week 8: Uvea 2 & Ciliary Body

Question 1

What is the ciliary body?

Answer 1

> A highly vascular pigmented structure with special involvement in:

• Accommodation
• Production of aqueous
• Production vitreous constituents

> Anterior (front) border is marked by the scleral spur
Posterior (back) boundary occurs at the ora serrata (which is where the nose-retina(?) begins)

Question 2

What’s the pars plicata and pars plana?

Answer 2

> Anterior part has many ridges (finger-like) (ciliary processes)
- called Pars Plicata
Further back posterior part is smooth – Pars Plana
The suspensory fibres (or zonules) of the lens run from the Pars Plana pass through the ciliary process of the pars plicata and attach to the lens capsule (hold lens in place).

Question 3

What are the three main structures of the ciliary body?

Answer 3

Supraciliaris
Stroma
Epithelium

Question 4

What’s the supraciliaris?

Answer 4

> Lines the sclera from the scleral spur to the choroid with which it blends posteriorly
A transition zone from the ciliary stroma to the sclera
Consists of strands of collagen interlaced with fibroblasts and melanocytes
Unlike sclera, has melanocytes that are pigmented

Question 5

What is the stroma?

Answer 5

-The bulk of the stroma is filled by the ciliary muscle

> The muscle is anchored to the scleral spur anteriorly and its fibres pass posteriorly into the stroma of the choroid.

Question 6

What are the three groups the ciliary muscle is divided into (smooth muscle fibres)

Answer 6

• Longitudinal Fibres: extend from the scleral spur to the choroid
• Radial Fibres: - also called oblique fibres.
• Circular Fibres: - have a sphincter like orientation close to the iris root.

Question 7

What is the effect of,contraction of the ciliary muscle?

Answer 7

To reduce tension on the suspensory fibres of the crystalline lens and produce accommodation. Lens becomes more convex-increases dioptric power.

Question 8

What does the lens have to make it spherical?

Answer 8

has elastic capsule around it to make lens spherical, unaccomidated eye = pull on that by contracting ciliary body release tension and allow to take up more spherical shape

Question 9

How many times is the pars plicata folded? (And what’s within these processes)

Answer 9

The pars plicata is folded into about seventy to eighty processes, and the stroma within these processes is packed with fenestrated capillaries which supply constituents for the production of aqueous humour

Question 10

What is the epithelium?

Answer 10

• A double layer of cells extending from the iris root to the retina (ora serrata).
• The deep layer consists of pigment epithelial cells linked to each other and the unpigmented cells in the superficial layer by desmosomes (adhesive protein, intracellular junctions, maintain mechanical integrity of tissues).

Question 11

What do the unpigmented cells in the pars plicata?

Answer 11

• The unpigmented cells in the pars plicata contains many mitochondria and rough endoplasmic reticulum. (metabolically active and involved in protein synthesis).
• The cells along the ridges of the ciliary processes contain large amounts of glycogen, an energy source
• • The unpigmented cells of the pars plana also contain large quantities of endoplasmic reticulum but fewer mitochondria

Question 12

What major arterial circle does the ciliary body contain?

Answer 12

• The ciliary body contains the major arterial circle (MAC) (also blood supply to the iris) near it’s attachment to the root of the iris.
• annular ring shaped vessel

Question 13

Where does the ciliary muscle get the energy for contraction from?

Answer 13

• Recurrent vessels pass from MAC to the choroid and branches supply the capillary bed in the ciliary processes and the vessels of the ciliary muscle supplying energy for contraction.

Question 14

What veins are responsible for venous drainage?

Answer 14

Venous drainage is mainly via the vortex veins (4) posteriorly, and to a lesser extent the anterior ciliary veins (venous return for anterior ciliary arteries).

Question 15

What is the nerve supply in the ciliary body?

Answer 15

• In the supraciliaris and stroma are sensory neurones passing back from the anterior regions of the eye to join the ciliary nerves.
• Autonomic parasympathetic nerve fibres are found in the supraciliaris and stroma, en route to the iris (producing miosis) and supply the ciliary body (producing accommodation).
• Sympathetic neurones are also present, some travelling to the iris (producing mydriasis), whilst those that terminate in the ciliary body may produce vasoconstriction.