L3 sclera Flashcards
1
Q
What is the sclera?
A
- an avascular structure
- white in colour
2
Q
What are the functions of the sclera?
A
- Support The Eye
- Protects The Eye from injury
- Anchorage for structures inside and outside the globe
3
Q
What is the sclera made up of?
A
75% collagen and proteins (in the sclera stroma)
25% mucopolysaccharide
4
Q
Describe the sclera in terms of its position and openings
A
the exposed area:
- the sclera is continuous with the cornea and the limbus( the transition zone between the cornea and sclera)
the rest of the sclera:
- enveloped by a thin membranous capsule known as the tenon’s capsule
- > this capsule serves to separate the sclera from the orbit fat
- the sclera is NOT a continuous outer coat of The Eye. It has several openings
- > these opening allows blood vessels and nerves to the eye as well as sites of attachment of the recti muscles
- > the sclera is the thinnest where the recti muscles are attached to it
5
Q
What are the layers of the sclera?
A
- Episclera
- Sclera stroma
- Lamina fusca
6
Q
What is the episclera?
A
- it is highly vascularised
- it is supplied with vessels from the anterior ciliary arteries
7
Q
What is the sclera stroma?
A
- it is avascular
- it consists of loose fine collagen fibres that are of variable thickness and are arranged randomly
- > this increases the strength of the sclera, making it tougher
- > the irregular arrangement also makes the sclera opaque
8
Q
What is the lamina fusca?
A
- it is the innermost layer of the sclera
- it is formed by collagen fibres
- > it is faintly brown (unlike the rest of the white sclera) due to the presence of melanocytes
- it is separated from the choroid by the perichoroidal space
- > within the space, runs the long and short posterior ciliary arteries and nerves
9
Q
What is the nerve supply of the sclera?
A
Sclera is innervated by the trigeminal nerve (5th/ V cranial nerve)
10
Q
What is the blood supply of the sclera
A
- anterior and posterior ciliary arteries
