Histology of the eye Flashcards
4 histological layers of the eyelid
- outermost layer
- orbicularis oculi; muscle layer
- tarsal plate with stromal layer
- innermost palpebral conjunctival layer
Outer layer of the eyelid
Haired keratinised stratified squamous epithelium and tactile hairs
- sebaceous glands; glands of Zeiss
- sweat glands; glands of Möll
Innermost layer of the eyelid
Lined with palpebral conjunctiva, continuous with bulbar conjunctiva and corneal surface at limbus
- conjunctival epithelium can be stratified columnar or stratified squamous
Tarsal plate
Plate of dense connective tissue between dermis of skin and lamina propria of the conjuctiva
- contains modified sebaceous glands; Meibomian Glands
Tarsal plate
Plate of dense connective tissue between dermis of skin and lamina propria of the conjunctiva
- contains modified sebaceous glands; Meibomian Glands
Nictitating membrane
Semi-circular fold of conjunctiva enclosing a plate
of cartilage
Lacrimal Apparatus
- Lacrimal Glands; Tubuloacinar, serous (cats), seromucous (horse, ruminant, dog and pig)
- Lymphoid follicles; Seen in lamina propria of nictitating membrane
The globe
- Corneo-scleral layer
- Uveo-vascular layer
- Retinal tunic
Cornea
- avascular; transparent when healthy
-if vessels; respond to inflammation (neovascularisation) - Oedema; swelling with fluid makes cornea cloudy
- Formed collagenous stroma and mucoid ground substance
- Outer surface is non-keratinised stratified squamous epithelium with basement membrane (Bowman’s membrane)
- Inner surface of the cornea is Descemet’s membrane
- Descemet’s membrane has simple squamous epithelium on inner surface- corneal endothelium
Injuries to the cornea
- erosion; loss of epithelium
- ulcer; loss of epithelium with a break in the basement membrane
- Use fluorescein dye; binds to collagen fibres, if applied to healthy cornea, washes away
Sclera
- dense collagenous stroma with few elastic fibres
- attached to the middle tunic (choroid) by the lamina fusca (layer of pigmented connective tissue)
- optic nerve passes through the sclera at the lamina cribrosa
Areas of Uvea
- posterior uvea; choroid
- ## anterior uvea; ciliary body & iris
Ciliary body
- anterior continuation of the choroid
- inner surface is a continuation of non-light-sensitive retina
- stroma contains ciliary muscle (smooth)
- basal epithelial layer; pigmented columnar cells
- surface epithelial layer; non-pigmented columnar cells
Choriocapillary layer
contains the capillary network that supplies the retina with blood
Tapetum lucidum
- between choriocapillary and vascular layers of the choroid in the dorsal part of the eye
Iris
- most anterior portion of the uvea
- attached to the ciliary body
- connective tissue stroma supports many blood
vessels and contains pigment cells - only posterior surface has pigment cells
- anterior surface has melanocytes and fibrocytes
- corpora nigra; black masses suspended from rim of pupil in ungulates
Layers of the photosensitive retina
1) Retinal pigmented epithelium
2) Rods and cones; photoreceptors
3) Outer limiting membrane
4) Outer nuclear layer
5) Outer plexiform layer
6) Inner nuclear layer of bipolar neurones
7) inner plexiform layer
8) ganglion cell layer
9) nerve fibre layer
10) inner limiting membrane
Cavities of the eye
- anterior segment; aqueous humour. Anterior chamber (behind cornea in front of iris and lens) and posterior chamber ( behind iris in front of ciliary body)
- Posterior segment; vitreous humour; cavity behind the lens
THE LENS
- lens capsule; basement membrane of lens epithelium, elastic properties
- lens epithelial cells; proliferation zone, nuclear bow and elongation and turnover of LECs
- lens fibres
-lens sutures
