Histology Department Medical Faculty Padjadjaran University

1. THE EYE-VISION (The Photoreceptor System) Histology Department Medical Faculty Padjadjaran University

2. V.A. A.P. Cornea Posterior chamber Conjunctiva Limbus Chamber iris Anterior Canal of Schelemn Ciliary muscle Lens Zonula ciliaris Med. rectus Lat. rectus Ora serrata Ciliary body Vitreous Lamina cribrosa Sclera Choroid Fovea Retina Dura Optic nerve P.P. Schematic horizontal meridional section of right eye

3. T.Fibrosa (External Layer) Sclera Cornea Layers Choroid T.Vasculosa (Middle Layer) Ciliary Body Iris Eyeball T. Nervosa (inner Layer) Retina ORGAN OF VISION Lens Fills Anterior Chamber Posterior Chamber Vitreous Body Accessory Structure (Adnexa) Eye Lids Tears Gland Muscles

4. TUNICA FIBROSA • SCLERA • Opaque • White • Posterior five sixth of the external layer • Consists of: • Flat Collagen Bundles • Ground Substance • Fibroblasts • Episclera, Tenon’s Space, Tenon’s capsule • Suprachoroidal lamina

5. CORNEA • Transparent • Colorless • Anterior one sixth of the external layer • Consists of 5 layers: • Layer of epithelium • Bowman’s membrane • Substantia Propria • Descement’s membrane • Endothelium Avasculer structure, receives its metabolizes by: diffusion from adjacent vessel and from fluid of the anterior chamber

6. Conjunctiva C A B D Photomicrographs of a transverse section of cornea. A : The Cornea and conjuctiva seen at low magnification. B : The posterior corneal epithelium – also called endothelium (arrows indicate Descemet’s membrane). C : Conjuntival epithelium. D : Anterior corneal epithelium. Note the smooth contour of the surface of this epithelium.

7. Layers of epithelium: • Stratified squamos epithelium • 5-6 cells layers • Deepest : columnar • Next : polyhydral • Surface : flat in shape • Bowman’s membrane: • A thin layer • Appears homogenous • Structureless under the light • microscope

8. Substantia propria • 90% of the thickness • Composed: • Collagenous fibrils arranged in lamellae (parallel with the surface) • Mucoid cement • Cells • Descement’s membrane: • Appears homogenous • Fibrous protein of collagen type • Endothelium: • Single layers of cells • Low cuboidal epithelium

9. LIMBUS (Corneoscleral Junction) • Area of transition from transparent collagen bundles of the cornea to the white opaque fibers of the sclera • The corneal epithelium, as it passes over into the limbus, increases in thickness up to ten or more cells • The corneal stroma losses its regular lamellar arrangement • In the stromal layer, irregular endothelium – lined channels, the trabecular mesh work, merge to form the canal of Schlemm

10. Canal of schlemm Cornea Limbus Anterior chamber Lens Ciliary muscles Zonule Iris Ora serrata Posterior chamber Ciliary body and process Vitreous body Choroid Photosensitive retina Sclera Sclera Optic papilla Fovea Sclera Choroid Pigment epithelium Optic nerve • Diagram of the right eye, seen from above, showing the structure of the eye, retina, fovea and ciliary body. Arrows in the anterior chamber show the direction of flow of aqueous humor. An enlarged diagram of the fovea is shown at lower right. • Axons of ganglion cells • Bipolar cells • Rods • Cones

11. TUNICA VASCULOSA • A. CHOROID • Divided into four layers: • The Suprachoroid, lamina suprachoroidea or epichoroid • Consist of lamellae, each lamella: very thin membrane • Vessel layer (stratum vasculosa) • Outer layer : large vessels • Inner layer : medium sized vessels

12. 3. The capillary layer (Lamina Choriocapillaris). • Serves of nutrition for the outer layers of the retina • 4. The lamina Vitrea, lamina elastica / basalis, or • membrane of Bruch: • Non cellular membrane • Two layers: • The outer elastic lamellae, very thin • The inner cuticle lamellae, relatively thicker

13. Section through retina, choroid and sclera. Sc. Ch = Choroid; Ret = Retina; 1 = Suprachoroid; 2 = Vessel layer; 3 = choriocapillaris 4 = Lamina vitrea 5 = Pigment epithelium 6 = layer of rods and cones 7 = external limiting membrane 8 = outer nuclear layer 9 = outer plexiform layer 10 = inner nuclear layer 11 = inner plexiform 12 = ganglion cell layer 13 = nerve fiber layer 14 = internal limiting membrane 1 Ch. 2 3 4 5 6 7 8 9 10 Ret. 11 12 13 14

14. B. CILIARY BODY • Two zones: • The orbiculus ciliaris (Pars Plana) • The posterior two thirds • Appears darkly pigmented • Relatively smooth • The corona ciliaris (Pars Plicata) • The anterior third • Bears some 70 to 80 radially arranged ridges, the ciliary processes

15. Circumlental space Zonula fibers Lens Ciliary processes Ora serrata Orbiculus ciliaris Ora serrata, ciliary body, zonula ciliaris and lens as viewed from behind after removal of the vitreous body

16. IRIS • A thin circular diapraghma • A circular aperture: the pupil • Divides the space between the cornea and the lens into two chambers: • The anterior chamber • The posterior chamber

17. V.A. A.P. Cornea Posterior chamber Conjunctiva Limbus Chamber iris Anterior Canal of schelemn Ciliary muscle Lens Zonula ciliaris Med. rectus Lat. rectus Ora serrata Ciliary body Vitreous Lamina cribrosa Sclera Choroid Fovea Retina Dura Optic nerve P.P. Schematic horizontal meridional section of right eye

18. Layer of iris is five layers: • Endothelium • A very thin delicate layer • Difficult to demonstrate in sections • Best shown after treatment with silver nitrate

19. The anterior border layer • The color of the iris upon: • The thickness of the anterior border layer • And the degree of pigmentation of it cells • In the brown iris: • The layer is thick • The cells heavily pigmented • In the blue iris: • The layer is thin • The cells minimum amount of pigment

20. The vessel’s layer (stroma) - Consists of a great number of blood vessel • M. Sphincter pupillae: - In the pupillary zone Contraction: Reduced the diameter of the pupil - The dilatator pupillae Contraction: Dilatation of the pupil • The pigment epithelium

21. Stroma Anterior border layer Endothelium Sphincter pupillae Pigment epithelium Horizontal section through pupillary zone of human iris

22. TUNICA NERVOSA • Consists of two portions : • The posterior portion is photosensitive – pars optica retinae • The anterior part is not photosensitive – pars coeca retinae. Constitutes the inner lining of the ciliary body and the posterior part of the iris The retina forms the pars optica retinae. The scalloped anterior border of the retina is known as the orra serrata.

23. Sclera Epithelium Choroid Photomicrograph of a section of retina in the transition (arrow) between the photosensitive (at left) and blind (at right) parts. This transition is called the ora serrata. Note the pigment epithelium, the choroid and the sclera.

24. RETINA • The retina consists of ten layers , • except at : • The fovea centralis • The optic disc (optic papillae) • The extreme periphery

25. Canal of schlemm Cornea Limbus Anterior chamber Lens Ciliary muscles Zonule Iris Ora serrata Posterior chamber Ciliary body and process Vitreous body Choroid Photosensitive retina Sclera Sclera Optic papilla Fovea Sclera Choroid Pigment epithelium Optic nerve • Diagram of the right eye, seen from above, showing the structure of the eye, retina, fovea and ciliary body. Arrows in the anterior chamber show the direction of flow of aqueous humor. An enlarged diagram of the fovea is shown at lower right. • Axons of ganglion cells • Bipolar cells • Rods • Cones

26. Development of the retina : • The retina derived from an evagination of the anterior cephalic vesicle or prosencephalon • As this co-called optic vesicle comes into contact with the surface ectoderm, it gradually in vaginates in its central region forming a double – walled optic cup. • In the adult : • The outer wall gives rise to a thin membrane called the pigment epithelium • The inner layer is derived the optical or functioning part of the retina

27. Diagrams of 4 stages in the development of the eye Lens Vesicle

28. Layer of the RETINA : • Pigment epithelium • Layers of rods and cones • External limiting membrane • Outer nuclear (or granular) layer • Outer flexiform (or molecular) layer • Inner nuclear (or granular) layer • Inner flexiform (or molecular) layer • Ganglion cell layer • Nerve fiber layer • Internal limiting membrane

29. 4. Collagenous fibers 1. Sclera 5.Chromatophores 2. Choroid 6. Blood vessel 7. Pigment epithelium 8. Rods and cones 9. Outer limiting membrane 10. Outer nuclear layer 3. Retina 11. Outer plexiform layer 12. Inner nuclear layer 13. Inner plexiform layer 14. Ganglion cell layer 15. Nerve fiber layer 16. Inner limiting membrane RETINA, CHOROID AND SCLERA

30. 16. Sclera 17. Suprachoroid layer (lamina fusca)with chromatophores 1. Blood vessels of the choroid 18. Vascular layer of the choroid 2. Chromatophores 19. Choriocapillary layer 3. Pigment cells in the retina 20. Processes of pigment cells extending between rods and cones 4. Rods 21. Cones 5. Cones 22. Rod 6. Outer limiting membrane 23. Outer limiting membrane 24. Nuclei of cones 7. Nuclei of cones 25. Nuclei of rods 8. Nuclei of rods 26. Outer processes of Muller’s cells 9. Outer plexiform layer 27. Synapses between horizontal and visual cells 28. Synapses between cones and bipolar cells 10. Nuclei of bipolar, horizontal, amacrine and Muller’s cells 29. Bipolar cell 30. Muller’s cell 31. Amacrine cell 32. Synapses between processes of bipolar, amacrine and ganglionic cells 11. Inner plexiform layer 33. Ganglion cell 12. Ganglion cell layer 34. Fiber of optic nerve 13. Muller’s fibers 14. Axons of ganglion cells 35. Horizontal fiber 15. Inner limiting membrane 36. Inner limiting membrane 37. Inner fibers of Muller’s cells

31. THE ROD CELLS AND THE CONE CELLS • The rod cells : • Photo pigment : Visual purple or rhodopsin • Each retina has about 120 million rods • Sensitive to light and the receptors used when low levels of light

32. The Cone cells : • Photo pigment : iodopsin • Each retina has about 6 million cones • Sensitive only to light of a higher intensity • Maximum sensitive is in the red, green or blue of the visible spectrum

33. Discs Outer segments Cilium Narrow collar Inner segments Outer limiting membrane (Composed of terminal bars and filaments of mueller cells) Nuclei Synapses Mueller cell cytoplasm Processes of bipolar cells

34. The light and the nervous impulses travel in the retina Diagram showing the arrangement of the three layers of neurons in the retina. Observe that the light and the nervous impulses travel in opposite directions.

35. LENS • Transparent • Biconvex, posterior surface has a greater convesity than the anterior surface • Three structural component : • Lens capsule : homogenous • Subcapsular Epithelium • Single layer of cuboidal epithelium cells • Present only on the anterior surface • Lens Fibers : • Appear as thin flattened structures • They are highly differentiated cells derived from cells of the subcapsuler epithelium

36. The lens, viewed from behind and from the side. From section through margin of lens longitudinal sections of lens fibers and transition from epithelium to lens fibers. a : Lens fibers; b: capsule; c : epithelium

37. The lens is held in place by the zonula ciliaris (Zonula of Zinn, suspensory ligament) • The Zonula on : • The lens capsule • The ciliary body The zonula is important in process accomodation

38. Connective tissue Lens Anterior view of the ciliary processes showing the zonules attaching of the lens. Zonule fibers are bundles of microfilaments (oxytalan fibers) from the elastic fibers system. The zonules form column (A) on either side of the ciliary processes (B), which meet on a single site (C) as they attach to the lens.

39. THE VITREOUS BODY • Transparent gell • Amorphous • Intercellular substance • Bounded by : • The internal limiting membrane of the retina • The lens • The posterior zonular membrane

40. 10. Superior tarsal muscle (of Muller) 1. Hair follicles 11. Adipose tissue 2. Sweat glands 12. Accessory lactrimal gland (of Krause) 3. Epidermis and dermis 13. Lymphatic tissue 4. Rudimentary hari follicle 5. Palpebral part of orbicularis oculi muscle 14. Epithelium of palpebral conjuctiva 15. Tarsal glands (Meibomian glands) 6. Connective tissue 16. Tarsus 17. Palpebral conjuctiva 7. Arteriole 8. Ciliary glands : large sweat glands (of Moll) 18. Duct of tarsal gland (Meibomian gland) 19. Ciliary muscle (of Riolan) 9. Sebaceous glands (of Zeiss) 20. Hair follicles of eyelashes Accessory structures A. EYELIDS

41. B. Lacrimal Apparatus • Consists of : • The lacrimal gland • Canaliculi • Lacrimal sac • Nasolacrimal duct

42. The Lacrimal Gland : • Tear secreting gland • Located in the anterior superior temporal portion of the orbit • Consist of several separate glandular lobes • Tubulo alveolar • Serous type • Myoepithelial cells surround the secretory portions

43. 6. Venule 1. Glandular alveoli 7. Interlobular duct 8. Glandular alveoli 2. Intralobular ducts 3. Myoepithelial cell (basal or basket cell) 9. Interalveolar connective tissue 10. Arteries 4. Interlobular connective tissue 5. Outpocketing of glandular cells 11. Interlobular duct LACRIMAL GLAND

44. Lacrimal Gland Cornea, Bulbar and palpebral conjunctiva Lacrimal Puncta Lacrimal Canaliculi Lacrimal Sac Nasolacrimal Duct Inferior meatus of nasal cavity DRAINAGE OF TEARS

45. THE LACRIMAL DRAINAGE SYSTEM