Batari Todja Umar

HISTOLOGY OF THE EYEHISTOLOGY OF THE EYE

Spherical structure, ± 25 mm in diameter Suspended in the bony orbital socket 6 extrinsic

muscles Wall of the eye 3 concentric layers

Fibrous tunic Vascular tunic Nerve tunic

THE EYE

A thick fibrous layer, covers the posterior 5/6 of the eyeball

Divided into 3 layers : Episclera

External layer Loose connective tissue adjacent to

the periorbital fat Stroma (Substantia propria)

= Tenon’s capsule Composed of dense network of thick

collagen fibers

SCLERASCLERA

• Lamina Fushcae Inner aspect, adjacent to the choroid

Contains of thinner collagen & elastic fibers

Melanocyte

Function :Protects & maintains the shape and the volume of the eyeball

• Transitional zone between the cornea & sclera

• 1.5 – 2 mm wide, 1 mm thick

• Iridocorneal angle apparatus for the outflow of the aqueous humor trabecular meshwork

Corneoscleral LimbusCorneoscleral Limbus

Transparent, 0.5 mm thick at the center, avascular, 5 layers

Cornea

Corneal epithelium

• Non-keratinizing squamous epithelium

• Basal cell layer gives rise to 5-7 superficial layers

• Free nerve endings terminate in this epithelium

• Adheres to the adjacent cells by desmosomes

Bowman’s Membrane• ± 8-10 µm thick• Composed of fine

collagen fibrils• Barrier to the

spread of infection• Not regenerate

Corneal stroma• Constitutes 90% of

the corneal thickness

• Composed of about 60 thin lamellae

• Each lamellae consist of parallel bundles of colagen fibrils

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Descemet membrane• Basal lamina of

endothelial cells• Homogen• Elastic,

transparent• 7 – 10 µm

Corneal endothelium• A single layer of

squamous cells • Metabolic exchange

between the cornea & aqueous humor

• Precise regulation of the water content of the stroma maintain the transparency

• Physical & metabolic changes corneal swelling

The most anterior part of the vascular tunic, forms a contractile diaphragm in front of the lens, a circular apperture (pupil) changes in size in response to the light intensity. Eye colour is determined by the relative number of melanocytes

IRISIRIS

Composed of 4 layers Anterior limiting membrane

Fibroblastic & melanocyte cells Stroma

Loose fibrocollagenous support tissue Blood vessels, nerve, melanin pigment Sphincter muscle of the pupil

Epithelial layer • Anterior non-pigmented

epithelium • Dilator pupillae muscle

• Posterior pigment epithelium• Faces the posterior chamber of the eye

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• Triangular shape • Extends from the base of the iris to the ora serrata

• 2 anatomical regions• Pars plica • Pars plana

• Function :• Aqueous humor production• Acomodation process

Cilliary Body

• The layers are similar to the iris

• Consist of :• Stroma

• Outer layer of smooth muscle cilliary muscle

Meridional (longitudinal portion)

Radial (oblique portion)

Circular portion

• Inner vascular region extends into the cilliary process

Continuous with the vascular layer of the choroid

• Epithelial layers• 3 principal functions

• Secretion of aqueous humor• Paticipation in blood aqueous barrier• Secretion & anchoring the zonula fibers

• The inner cells layer non-pigmented• The outer cells layer pigmented

• Dark-brown vascular sheet, 0.25 mm thick posteriorly, 0.1 mm thick anteriorly

• Lies between the sclera & retina

• Supports the retina• Contains of :

• Suprachoroid lamina• ± 30 µm thick• Loose connective

tissue• Choroidal stroma

• Numerous venules & arterioles

• Haller layer (outer part)

• Sattler layer (inner part

CHOROID

Choriocapillary• Capillary layer supporting the deep layer of the retina • Diameter 40 – 60 µm• Thin wall

4. Bruch’s membrane• 1-4 µm thick• Interface between the choroid & the retinal pigment

epithelium

10 layers1. Retinal pigment

epithelium2. Photoreceptor cells3. Outer limiting membrane4. Outer nuclear layer 5. Outer plexiform layer6. Inner nuclear layer 7. Inner plexiform layer 8. Ganglion cells9. Nerve fiber layer10. Inner limiting

membrane

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RETINA

Retinal Layers

Retinal Pigment Epithelium

Photoreceptor cells

• LENSTransparent, avascular, biconvex Suspended between the edges of cilliary body zonula fibers9 mm in diameter, 3.5 mm thick Capsule

• A thick basal lamina• Produced by the anterior lens cells

Subcapsular epithelium Cuboidal layer of cells Only on the anterior surface of the lens

Lens fibers Derived from subcapsular epithelial cells

REFRACTIVE MEDIA OF THE EYE

• Vitreous Body

• Between the lens & the retina • Transparent gelatinous structure• Attach to the surrounding structures • Main portion is homogenous gel containing 99% water, collagen, hyaluronate acid

• Avascular

• Conjunctiva• A translucent membrane• Extends from corneoscleral limbus - internal surface of the eyelid

• 2 layers• Stratified columnar epithelium

Goblet cells mucin• Lamina propria

Loose connective tissue Blood vessels & lymphatic vessels

ACCESORY COMPONENTS OF THE EYE

• Palpebra• Upper & lower eyelid • Protection of the eye • Contains of :

• Skin• Orbicularis oculi muscle

• Tarsal plate• Conjunctiva• Glands

Meibomian glands Sebaceous type Oily layer of the tear film

Embedded in the tarsal plate

Glands of Zeis Sebaceous glands

Glands of Moll Apocrine sweat glands

Glands of Krause Fornix conjunctiva

Glands of Wolfring Above the tarsal plate

Lacrimal apparatus• Lacrimal glands

• Upper lateral side of the orbit

• 2 parts : orbital & palpebral parts

• 10 – 20 ducts• Several separate lobules of tubuloacinar serous glands

• Drains into the upper fornix

• Wash over the surface of the eye

• Tears drain from the eye through lacrimal puncta

• Lacrimal canaliculi at medial angle,

• Merge into common lacrimal duct

• Open into lacrimal sac, pseudostratified ciliated epithelium

• Continuous to nasolacrimal duct open to nasal cavity below the inferior turbinate