66. The eyeball - middle (vascular) coat - parts, description.

FIBROUS LAYER of the eyeball

• The eyeball consists of three layers: fibrous, vascular & nervous (retina)

Gives mechanical stability to the eyeball.

• Eyeball: spherodial sensory organ that recieves the visual stimuli & convays them to the brain.
• The fibrous layer consists of two componants:

1. The sclera
2. The Cornea.

The Sclera:

• Covers the posterior & lateral parts of the eyeball. (~85%)
• It is an opaque, white layer of dense connective tissue.
• It is pierced by neumerous vessels & nerves, including the optic nerve posteriorly
• Provides attachment for the extraocular muscles.
• Covered by the fascial seath externally & internally is loosely attached to the choroid of the vascular layer.
• Composed of 3 layers:

1. Episclera
2. Scleral stroma
3. Lamina fusca - "pigmented"

The Cornea:

• Is a clear, dome-shaped structure, covers the anterior 1/6 of the surface of the eyeball.
• Transparent:
• ↳ Transperancy allowing light to pass through & enter the eye.
• ↳ the lack of blood vessels in the cornea contributes to its clarity
• Consists of 5 layers:

1. Epithelium
2. Bowman's layer
3. Stroma
4. Descemet's membrane
5. Endothelium.

outer ↓ Inner