1. Medical School Histology Basics Eye
VIBS 289 lab
Larry Johnson Texas A&M University

2. OUTLINE OVERVIEW CELLULAR STRUCTURES THROUGH WHICH LIGHT PASSES
Aqueous humor
OUTLINE
OVERVIEW
CELLULAR STRUCTURES THROUGH WHICH LIGHT PASSES
CORNEA
LENS
RETINA
STRUCTURES WHICH INFLUENCE THE IMAGE
IRIS
CILIARY BODIES
TRABECULAR MESHWORK
Vitreous humor

3. Aqueous
humor
VITREOUS BODY
(VITREOUS HUMOR)

4. 34412

5. Eye – conjuctiva on white of eye
192
Eye – conjuctiva on white of eye
sclera
Conjunctiva
Stratified squamous
epithelium with
some goblet cells

6. Eye 192 human and 34412 monkey Aqueous humor 192 34412
Connective tissue
Aqueous humor
Nerve
Posterior chamber
192
Retina
Cornea
Sclera
Pupil
Optic nerve
Anterior chamber
What is the function of the canal of Schlemm
The canal of Schlemm functions to drain the aqueous humor from the anterior chamber.
Where is aqueous humor produced?
Aqueous humor is produced by ciliary processes. It then flows into the posterior chamber of the anterior cavity, through the pupil into the anterior chamber, and finally drains through the canal of Schlemm.
What is the ora serrata?
The ora serrata is the serrated junction between the retina and the ciliary body.
What are the functions of the pigment epithelial layer of the retina?
Absorbs scattered light that passes through the neural layer
Part of the protective blood-retina barrier isolating retina photoreceptors from the highly vascular choroid and regulating ion transport between these compartments.
Role in retinal regeneration
Phagocytosis of shed components from the adjacent photoreceptors and degradation of this material
Removal of free radicals by various protective antioxidant activities and support of the neural retina by secretion of ATP, various polypeptide growth factors, and immunomodulatory factors
The sphincter pupillae muscle is innervated by what portion of the nervous system?
Parasympathetic innervation
What are fovea centralis and the macula lutea?
Fovea centralis: a shallow depression with only cone cells at its center; ganglion cells and other conducting neurons are located only at its periphery. It lies directly opposite of the pupil and is where visual acuity or sharpness is maximal.
Macula lutea: This surrounds the fovea centralis. Here all layers of the retina are present and the two plexiform layers are rich in various carotenoids, which give the area a yellowish color. The carotenoids have antioxidant properties and filter potentially damaging short wavelength light, thus helping to protect the cone cells of the fovea.
What is the effect of light on the cGMP-gated sodium channel in the photoreceptor cell?
Light > absorbed by retinal of rhodopsin > isomerize from 11-cis-retinal to all-trans-retinal > activates opsin > activate transducin > stimulates phosphodiesterase to hydrolyze cGMP > cGMP-gated sodium channels close > hyperpolarization of cell > decrease release of neurotransmitters at synapse > depolarizes sets of bipolar neurons > action potentials sent to optic nerve > brain produces image.
Lens
Iris
34412
Ciliary body
34412
Vitreous body
Chorioid layer

8. 192 Eye – corneal layers Stratified squamous Epithelium
Bowman's membrane
Corneal
endothelium
Corneal stroma
Corneal fibroblasts
Descemet's Membrane

9. corneal layers Iris of Eye (toluidine blue)
292
Ciliary muscle:
smooth muscle
Sclera
Lens
Sclera-cornea junction (limbus)
Bowman's membrane
Aqueous
humor
Corneal stroma
Aqueous
humor
Corneal
endothelium
Iris
Descemet's
Membrane
Iris
Anterior
chamber
Posterior chamber

10. 292 Ciliary muscle: smooth muscle
Ciliary processes
Blood vessel
lens
Nerves
Ciliary muscle
192

11. 192 Eye – ciliary muscle Iris Pupil Artifactual space Conjunctival sac
Sclera-cornea junction (limbus)
Ciliary muscle
Posterior chamber
Ciliary processes
Anterior
chamber
Ciliary muscle (smooth muscle)

12. 192 192 Eye – secretory cells Pigmented cells of the ciliary processes
become the dilator
muscle of the iris
Pigmented cells
Secretory cells
Secretory cells
become the
pigmented cells
of the iris
Iris
Ciliary processes

13. 292 Eye (toluidine blue) Conjunctiva Iris Ciliary muscle
Trabecular meshwork
Air
Canal of Schlemm
Anterior
chamber
Limbus
Endothelium of trabecular meshwork
is continuous with the transport endothelium of the cornea
Ciliary
processes
Iris
Posterior chamber

14. Eye – trabecular meshwork and canal of Schlemm
192
Eye – trabecular meshwork and canal of Schlemm
Canal of Schlemm
Ciliary muscle
Limbus
Trabecular meshwork
Anterior chamber with
aqueous humor

15. Iris 34412 Canal of Schlemm Trabecular meshwork Blood vessels
Posterior chamber with
aqueous humor
Monkey eye
34412

16. Eye (toluidine blue) 292 Iris Anterior chamber Dilator muscle
Lens
Anterior chamber
Dilator
muscle
Lens capsule
Lens
Iris
Posterior chamber
Iris
pupil
Cuboidal
epithelium
on anterior
surface of
lens
Constrictor
muscle
Iris
Pupil

17. 292 Eye (toluidine blue) Lens cuboidal epithelium Lens Lens capsule
Iris constrictor smooth muscle

18. The capsule is a shared basement membrane of the lens epithelium

19. The capsule is a shared basement membrane of the lens epithelium

20. Lens and iris 192 and 34412 Iris Iris Lens anterior surface 192
Pigmented
epithelium of iris
Iris
Lens capsule
Posterior chamber
Iris
Lens cuboidal
epithelium
34412
Iris constrictor muscle is smooth muscle

21. Eye (toluidine blue) elongation of lens cuboidal cells at bow region
292
Eye (toluidine blue) elongation of lens cuboidal cells at bow region
Lens cuboidal epithelium on its anterior surface gives rise to elongated lens fibers in the bow region, and the shared basement membrane of these cells is the capsule
Capsule
Lens cuboidal epithelium
Capsule
flattened lens fibers
No cuboidal
epithelium on the posterior surface of the lens and the capsule is thinner there
Artifactual space
34412

22. 34412 Eye monkey Sites of attachment of zonules to the lens’ capsule
Anterior surface
Eye monkey
Iris
Anterior surface
Posterior surface
Ligaments
(zonules)
lens
192
One site of attachment of a zonule to the capsule on the lens on its posterior surface
lens

23. 34412 Sclara Ciliary muscle Zonules 192 Lens fibers
Capsule and cuboidal epithelium on the anterior surface of lens
Thinner capsule on the posterior surface of the lens

24. Eye monkey 34412 Capillary network in retina Pigmented layer
of epithelial cells
Elaborate network
of vessels, the
choroid plexus.
Central artery
of the retina

26. 34412 Cones Rods Ganglion cell layer Bipolar cells Vitreous body
Retinal
pigmented
epithelium
Artifactual space
Photosensitive
portion of rod
and cone cells
Retinal
pigmented
epithelium
Artifactual space
Venule in the
choroid plexus
Sclera

27. Rods
Cones
Photosensitive portion of rod and cone cells
Nuclei of rod and cone cells
= outer nuclear layer
Retinal pigmented epithelium

28. Eye - Retina and choroid:
Blood vessels
in the retina
Artifact space
292
Choroid
Choroid plexus
Melanin
granules
Retina
Nucleus
Retinal
pigment
epithelium
Optic nerve

29. Retina (toluidine blue)
292
Bipolar cells
Artifactual space
Photoreceptor cells
Rods
Optic
nerve
Cones
Capillary

30. Macula with top two layers pulled back to aid vision
Typical retina
Macula with top two layers pulled back to aid vision
Ganglion cell layer
Bipolar cells
Rods and cones
Rods and cones
Retinal pigmented epithelium
Retinal pigmented epithelium

31. 192 Conjunctiva Cornea Sclera lens Choroid plexus Cornea Iris Sclera
Vitreous body
Retina
Lens
292
Anterior
chamber
Optic nerve
Posterior chamber
Aqueous
humor

32. 34412 Pigmented epithelium Blind spot where optic nerve enters Choroid
the retina
Choroid
Bipolar cell layer
Ganglion cell layer
Photosensitive region
of rods and cones

33. Eye (toluidine blue) 292 Blind spot where optic nerve enters
the retina

34. 34412
Choroid plexus
Retina
OPTIC CUP AND
NERVE HEAD
Retina

35. In summary

36. Questions on the eye
1. The integrity of the relationship among structures of the eye is produced/maintained by:
supporting layer of the eye holding pressure
precise regulation of pressure via aqueous humor production and outflow
the bony structure of the sclera in mammals
a and b
a, b, and c
2. Which structure is not correctly paired with its function?
a. the iris regulates the amount of light that reaches the retina
b. ciliary bodies alter the shape of the lens by the attached zonules
c. the trabecular meshwork enhances the outflow of vitreous humor
d. the cornea focuses the image on the retina
e. the retinal and choroid blood vessels provide nutrients to the retina
3. Which function(s) least match(s) that of the cornea?
a. protection
b. structural support
c. filter out undesirable light rays
d. focus image on photosensitive portion of the photoreceptor cells
e. none of the above

37. Many illustrations in these VIBS Histology YouTube videos were modified from the following books and sources: Many thanks to original sources!
Bruce Alberts, et al Molecular Biology of the Cell. Garland Publishing, Inc., New York, NY.
Bruce Alberts, et al Molecular Biology of the Cell. Garland Publishing, Inc., New York, NY.
William J. Banks, Applied Veterinary Histology. Williams and Wilkins, Los Angeles, CA.
Hans Elias, et al Histology and Human Microanatomy. John Wiley and Sons, New York, NY.
Don W. Fawcett Bloom and Fawcett. A textbook of histology. W. B. Saunders Company, Philadelphia, PA.
Don W. Fawcett Bloom and Fawcett. A textbook of histology. Chapman and Hall, New York, NY.
Arthur W. Ham and David H. Cormack Histology. J. S. Lippincott Company, Philadelphia, PA.
Luis C. Junqueira, et al Basic Histology. Lange Medical Publications, Los Altos, CA.
L. Carlos Junqueira, et al Basic Histology. Appleton and Lange, Norwalk, CT.
L.L. Langley, et al Dynamic Anatomy and Physiology. McGraw-Hill Book Company, New York, NY.
W.W. Tuttle and Byron A. Schottelius Textbook of Physiology. The C. V. Mosby Company, St. Louis, MO.
Leon Weiss Histology Cell and Tissue Biology. Elsevier Biomedical, New York, NY.
Leon Weiss and Roy O. Greep Histology. McGraw-Hill Book Company, New York, NY.
Nature ( Vol. 414:88,2001.
Arthur C. Guyton,1971.Textbook of Medical Physiology W.B. Saunders company, Philadelphia, PA
WW Tuttle and BA Schottelius Textbook of Physiology C.V. Mosby Co.
A.L. Mescher Junqueira’s Basis Histology text and atlas, 13th ed. McGraw

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