L4 uveal tract Flashcards
What is the Uvea?
- consists of:
1. Iris
2. Ciliary body
3. Choroid - is vascular and pigmented
- is a continuous structure with 2 openings
- > pupil anteriorly
- > optic nerve canal posteriorly
What are the functions of the uveal tract?
- Regulates the amount of light entering The Eye (by the iris)
- Produces and secretes aqueous humour (by ciliary body)
- Responsible for accomodation (ciliary body)
- Provides nutrients to outer retina (choroid)
What is the iris?
- The anterior most part of the uveal tract
- contains melanocytes that gives colour to the eye
- regulates the size of the pupil by the action of sphincter and dilator muscles
- 2 zones (pupillary and ciliary) seperated by the colarette
what are the 3 layers of the iris?
- anterior border layer
- contains melanocytes which give the iris colour - stroma
- contains the connective tissues, pigments, blood vessels and sphincter muscle (constricts the pupil) - pigment epithelium
- double layered
- both pigmented
- dilator muscles
order from anterior to posterior:
anterior border layer, iris stroma, iris sphincter muscle, iris dilator muscle, iris pigment epithelium
describe the anterior border layer
- anterior-most iris layer
- provides colour to the iris
describe the iris stroma
contains connective tissue, blood vessels and pigment cells
describe the sphincter muscle
- lies in the pupillary zone in the iris stroma
- encircles the pupil
- constricts the pupil
- parasympathetic innervation
describe the dilator muscle
- lies in the ciliary zone in the anterior epithelial region
- radially arranged
- dilates the pupil
- sympathetic innervation
describe the iris epithelium
- posterior-most iris layer
- double-layered
- both pigmented
describe dilator vs sphincter briefly
- dilator muscle is weaker
- sphincter and dilator muscles work in opposite directions, they are antagonistic to each other
what is the blood supply of the iris?
the major arterial circle (MAC) is formed from:
- two long ciliary arteries
- seven short anterior ciliary arteries
-> the MAC is located in the iris stroma towards the ciliary stroma
what is the nerve supply of the iris?
- trigeminal nerve (cranial nerve 5/v)
2. oculomotor nerve (cranial nerve 3/ lll) for pupillary actions
what is the ciliary body?
has 2 regions:
- pars plicata (ciliary processes)
- pars plana
from anterior to posterior/outer to inner, the layers are: 1. ciliary muscle 2. stroma 3 epithelium 3a. outer pigmented epithelium 3b. inner non-pigmented epithelium
describe the 3 layers of the ciliary body
- ciliary muscles (outermost layer)
- is responsible for the changes of lens shape for accommodation - stroma
- contains blood vessels, connective tissue, pigments - epithelium
- double-layered (outer pigmented and inner non-pigmented epithelium)
- the inner non-pigmented epithelium in the ciliary processes (pars plicata region) produces aqueous humour
describe the pars plicata
- has 3 layers (muscles, stroma and epithelium)
- anterior region of the ciliary body
- contains 70 radially arranged folds known as ciliary processes
- is closer to the iris
- aqueous humour is only produced in the ciliary processes (pars plicata region)
- inner-non pigmented epithelium in the pars plicata region is the site of aqueous production
describe the pars plana
- 3 layers (muscle, stroma and epithelium)
- posterior region of the ciliary body
- is the flatter region (extends from the posterior of the pars plicata to the ora serrata)
- located nearer to the choroid
- does NOT contain ciliary processes
describe the ora serrata
it is the transition between the ciliary body and the choroid
what is the blood supply of the ciliary body?
major arterial circle (MAC), it consists of:
- 2 long posterior ciliary arteries
- 7 short anterior ciliary arteries
- > it is located near the ciliary stroma (near the iris root)
what is the nerve supply of the ciliary body?
- trigeminal nerve (cranial nerve 5/ v)
- oculomotor nerve for accommodation (cranial nerve 3/lll)
describe the choroid
- it is the posterior-most uveal structure
- vascular and pigmented
- supplies nutrition to the outer retina
- has 4 layers (anterior to posterior) 1. suprachoroid - contains connective tissue, blood vessels and nerves - separates sclera and choroid
- stroma
- contains blood vessels and pigments - choriocapillaries (smaller blood vessels)
- supplies nutrition to the macula (outer retina) - Bruch’s membrane
- aids in the passage of nutrients to the retina
what is the choroid’s blood supply?
it is supplied by the posterior ciliary artery and anterior ciliary artery
what is the choroid’s nerve supply?
trigeminal nerve ( cranial nerve 5/v)
