DOCSLIB.ORG

Sheep Eye Dissection EYE

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Sheep Eye Dissection EYE Part I: The Eye Part II: Sheep Eye Dissection EYE The eye is an extension of the brain It helps us take in light information from our surroundings. Eye brain proximity • Can you see : • the optic nerve bundle? • Spinal cord? What are the parts of the eye? Cornea Cornea- transparent membrane that covers iris and pupil. Focuses light on the retina. Pupil, Iris, Sclera Pupil- hole passes different amounts of light Iris- colored part of the eye that controls the size of the pupil Sclera- “whites” of the eye that forms outer covering Aqueous Humor, Ciliary Muscle, Lens Aqueous Humor- nutritious fluid between the iris and the cornea. As we age, it breaks down and we begin to see “floaters” Ciliary Muscles- produces aqueous humor and controls lens shape Lens- Bends light rays to the back of the eye to retina. Retina is to receive light that the lens has focused, convert the light into neural signals, and send these signals on to the brain for visual recognition. Aqueous Humor, Ciliary Muscle, Lens Retina Blind Spot- site of optic nerve • Full of light receptors connection which are sensitive to: • Cones- Colour • Rods- Light levels • Massive blood supply is also needed Vitreous Humor, Blind Spot, Optic Nerve, Vitreous Humor- transparent jelly-like fluid that fills the eye and refracts light Optic Nerve- sends messages picked up by retina to the brain Blind Spot- area where optic nerve attaches. No retina is located there so information cannot be picked up; “Blind” Choroid Layer, Tapetum lucidum Choroid Layer- lies between the sclera and the retina it provides the blood supply to the eye. Tapetum lucidum- iridescent film under the retina that provides animals with “night vision” Cross Sclera section Choroid Layer You must know: Taptem lucidum 1. Lens 2. Cornea 3. Aqueous humor 4. Pupil Blind 5. Iris Spot 6. Ciliary Muscle 7. Sclera 8. Vitreous Humor 9. Retina 10. Blind Spot 11. Choroid Layer Ciliary 12. Optic Nerve 13. Tapetum Lucidum Eye Dissection • Before we go over the dissection, let’s review the parts of the eye and their function TIME TO BEGIN THE SHEEP EYE DISSECTION!!! Cut away fat using scissors Anterior External Eye Structure Posterior External Eye Structures • Select a place to make an incision of the sclera midway between the cornea and optic nerve. Use the point of a surgical scissors to make a small cut through the sclera. Fluid should ooze out of the eyeball when you have cut deeply enough. • Arrange the two hemispheres of the eye as you see in the photograph. • Observe the semi-fluid vitreous humor that fills the central cavity of the eye. It is transparent in the living eye but might be cloudy in the preserved specimen • The retina lines the the posterior cavity of the eye and extends forward to the ciliary body. Use your probe to lift and pull the retina back from the underlying choroid layer. • Notice that the retina is only firmly attached to the choroid at one place. This region is the optic disc or blind spot. Internal Eye Structure – Posterior Section Internal Eye Structures – Anterior Section Remove the lens and place against newspaper to see that it is a magnifier! • When the lens is removed, an opening, allowing light to enter the eye is seen. This opening, the pupil is located in the center of the iris. Note the oblong shape of the sheep pupil, in humans the pupil is circular. • The back side of the iris can be seen just above the pointer in the photograph. Can you identify the parts? You will need to so you can get credit during the lab Can you identify the parts? You will need to so you can get credit during the lab 1. Cornea 2. Sclera 3. Optic Nerve 4. Iris 5. Pupil 6. Ora Serrata (you do not have to know this structure!) 7. Ciliary Body 8. Choroid 9. Tapetum Lucidum 10. Retina 11. Lens 12. Vitreous Humor.
Load more

Recommended publications
  • Morphological Aspect of Tapetum Lucidum at Some Domestic Animals
    Bulletin UASVM, Veterinary Medicine 65(2)/2008 pISSN 1843-5270; eISSN 1843-5378 MORPHOLOGICAL ASPECT OF TAPETUM LUCIDUM AT SOME DOMESTIC ANIMALS Donis ă Alina, A. Muste, F.Beteg, Roxana Briciu University of Angronomical Sciences and Veterinary Medicine Calea M ănăş tur 3-5 Cluj-Napoca [email protected] Keywords: animal ophthalmology, eye fundus, tapetum lucidum. Abstract: The ocular microanatomy of a nocturnal and a diurnal eye are very different, with compromises needed in the arrhythmic eye. Anatomic differences in light gathering are found in the organization of the retina and the optical system. The presence of a tapetum lucidum influences the light. The tapetum lucidum represents a remarkable example of neural cell and tissue specialization as an adaptation to a dim light environment and, despite these differences, all tapetal variants act to increase retinal sensitivity by reflecting light back through the photoreceptor layer. This study propose an eye fundus examination, in animals of different species: cattles, sheep, pigs, dogs cats and rabbits, to determine the presence or absence of tapetum lucidum, and his characteristics by species to species, age and even breed. Our observation were made between 2005 - 2007 at the surgery pathology clinic from FMV Cluj, on 31 subjects from different species like horses, dogs and cats (25 animals). MATERIAL AND METHOD Our observation were made between 2005 - 2007 at the surgery pathology clinic from FMV Cluj, on 30 subjects from different species like cattles, sheep, pigs, dogs cats and rabbits.The animals were halt and the examination was made with minimal tranquilization. For the purpose we used indirect ophthalmoscopy method with indirect ophthalmoscope Heine Omega 2C.
    [Show full text]
  • Characteristics of Structures and Lesions of the Eye in Laboratory Animals Used in Toxicity Studies
    J Toxicol Pathol 2015; 28: 181–188 Concise Review Characteristics of structures and lesions of the eye in laboratory animals used in toxicity studies Kazumoto Shibuya1*, Masayuki Tomohiro2, Shoji Sasaki3, and Seiji Otake4 1 Testing Department, Nippon Institute for Biological Science, 9-2221-1 Shin-machi, Ome, Tokyo 198-0024, Japan 2 Clinical & Regulatory Affairs, Alcon Japan Ltd., Toranomon Hills Mori Tower, 1-23-1 Toranomon, Minato-ku, Tokyo 105-6333, Japan 3 Japan Development, AbbVie GK, 3-5-27 Mita, Minato-ku, Tokyo 108-6302, Japan 4 Safety Assessment Department, LSI Medience Corporation, 14-1 Sunayama, Kamisu-shi, Ibaraki 314-0255, Japan Abstract: Histopathology of the eye is an essential part of ocular toxicity evaluation. There are structural variations of the eye among several laboratory animals commonly used in toxicity studies, and many cases of ocular lesions in these animals are related to anatomi- cal and physiological characteristics of the eye. Since albino rats have no melanin in the eye, findings of the fundus can be observed clearly by ophthalmoscopy. Retinal atrophy is observed as a hyper-reflective lesion in the fundus and is usually observed as degenera- tion of the retina in histopathology. Albino rats are sensitive to light, and light-induced retinal degeneration is commonly observed because there is no melanin in the eye. Therefore, it is important to differentiate the causes of retinal degeneration because the lesion occurs spontaneously and is induced by several drugs or by lighting. In dogs, the tapetum lucidum, a multilayered reflective tissue of the choroid, is one of unique structures of the eye.
    [Show full text]
  • Microscopic Anatomy of the Eye Dog Cat Horse Rabbit Monkey Richard R Dubielzig Mammalian Globes Mammalian Phylogeny General Anatomy Dog
    Microscopic Anatomy of the eye Dog Cat Horse Rabbit Monkey Richard R Dubielzig Mammalian globes Mammalian Phylogeny General Anatomy Dog Arterial Blood Vessels of the Orbit General Anatomy Dog * Horizontal section Long Posterior Ciliary a. Blood enters the globe Short Post. Ciliary a Long Post. Ciliary a. Anterior Ciliary a. Blood Supply General Anatomy Dog Major arterial circle of the iris Orbital Anatomy Dog Brain Levator Dorsal rectus Ventral rectus Zygomatic Lymph node Orbital Anatomy Dog Orbital Anatomy Dog Cartilaginous trochlea and the tendon of the dorsal oblique m. Orbital Anatomy Dog Rabbit Orbital Anatomy Dog Zygomatic salivary gland mucinous gland Orbital Anatomy Dog Gland of the Third Eyelid Eye lids (dog) Eye lids (dog) Meibomian glands at the lid margin Holocrine secretion Eye lids (primate) Upper tarsal plate Lower tarsal plate Eye lids (rabbit) The Globe The Globe Dog Cat Orangutan Diurnal Horse Diurnal Cornea Epithelium Stromal lamellae Bowman’s layer Dolphin Descemet’s m Endothelium TEM of surface epithelium Cornea Doubling of Descemet’s Vimentin + endothelium Iris Walls: The vertebrate eye Iris Sphincter m. Dilator m Blue-eye, GFAP stain Iris Collagen Iris Cat Sphinctor m. Dilator m. Iris Cat Phyomelanocytes Iris Equine Corpora nigra (Granula iridica) seen in ungulates living without shade Ciliary body Pars plicata Ciliary muscle Pars plana Ciliary body Zonular ligaments Ciliary body Primarily made of fibrillin A major component of elastin Ciliary body Alcian Blue staining acid mucopolysaccharides: Hyaluronic acid Ciliary
    [Show full text]
  • CORNEAL VASCULARIZATION in the FLORIDA MANATEE (Trichechus Manatus Latirostris)
    CORNEAL VASCULARIZATION IN THE FLORIDA MANATEE (Trichechus manatus latirostris) By JENNIFER YOUNG HARPER A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 2004 Copyright 2004 by Jennifer Young Harper ACKNOWLEDGMENTS I would like to thank my mentor, Dr. Don Samuelson. He has been a wonderful source of knowledge, inspiration, and motivation. Without his help and guidance, I could not have accomplished any of this work. I would also like to thank Dr. Roger Reep for all of his help and support along the way. He too has acted as a rock and support system. My additional committee members (Dr. Peter McGuire, Dr. Dennis Brooks, and Dr. Gordon Bauer) have been tremendous support and I thank them for all they have offered. Their guidance has been appreciated beyond belief. Laboratory technologists Pat Lewis and Maggie Stoll were extremely helpful and supportive during much of my work. I would have not been able to accomplish the first procedure without their help. I thank these fine ladies from the bottom of my heart. My parents, Jim and Marion Young, have meant more to me than I can ever describe or explain. I appreciate all their love and support. Finally, I thank my husband Ridge Harper. He has been the strongest support system I could ever ask for and makes me happier than I ever knew I could be. iii TABLE OF CONTENTS page ACKNOWLEDGMENTS ................................................................................................
    [Show full text]
  • Tapetum Lucidum
    J. Anat. (1983), 136, 1, pp. 157-164 157 With 8 figures Printed in Great Britain Fine structure of the canine tapetum lucidum T. P. LESIUK AND C. R. BRAEKEVELT Department ofAnatomy, University ofManitoba, Winnipeg, Manitoba, Canada (Accepted 26 April 1982) INTRODUCTION Tapeta lucida are randomly distributed throughout the animal kingdom, being found primarily in animals that are dim light active (Walls, 1967). They are of diverse structure, organization and composition (Rodieck, 1973). Despite these differences, however, all act to increase retinal sensitivity by reflecting light back through the photoreceptor layer. Two types of vertebrate tapeta lucida are distinguished. The reflecting material may be located within the retinal epithelium (retinal tapetum lucidum), or it may be located in the choroid, external to the retinal epithelium (choroidal tapetum lucidum). Within choroidal tapeta lucida, the reflective material may be an array of extra- cellular fibres (tapetum lucidum fibrosum), or layers of cells packed with organized, highly refractive material (tapetum lucidum cellulosum) (Walls, 1967; Rodieck, 1973). Amongst the reflective materials noted in tapeta cellulosa are guanine/ hypoxanthine crystal plates, riboflavin crystal plates and rodlets of varying com- position. The rodlet type of tapetum lucidum cellulosum is characteristic of all of the Order Carnivora except the Family Viverridae (Duke-Elder, 1958). The bulk of the work reported on the rodlet type of tapetum lucidum cellulosum is on the cat (Murr, 1928; Lucchi, Callegari & Bartolami, 1978; Vogel, 1978; Bussow, Barmgarten & Hansson, 1980). It has been suggested that dogs, as well as possessing a well developed tapetum lucidum cellulosum, also have a retinal tapetum lucidum that may aid in the reflection of light by the choroidal tapetum (Walls, 1967).
    [Show full text]
  • How Does My Dog See?
    How does my dog see? How does my dog see? Everyone wonders about the vision of their pets. With this document I hope to bring you some answers. The vision includes many factors such as: visual field, depth perception (ability to evaluate a distance), visual acuity (ability to focus), movement perception, color perception. All these components of the vision need to be integrated by the brain to produce an effective vision. Although it is impossible to ask our pets to read a chart to evaluate their vision, the comparative studies allow us to assume some facts about the vision of our pets. Visual field – The visual field is much larger in dogs than in humans because of the position of the eyeballs, being in a much more lateral position. The visual field covers 250-287° (depending on the breeds) whereas it covers 180 ° in humans. Depth perception - The visual field simultaneously seen by both eyes is called binocular field. The binocular vision makes possible the perception of depth. The binocular field is reduced in dogs to 80-100 degrees in comparison to the one is human (140 degrees) due to the lateral position of the eyeballs. Movement perception – Dogs have a peripheral vision larger than humans. That’s the reason why dogs have a better ability to detect motion than humans. On the other hand, dogs see less detail as their central vision is less developed. Visual acuity - Dogs do not have a fovea or a macula (area of the retina where there is a high concentration of cones, the day receptors of the retina) and the optic nerve of the dog contains much less nervous fibers than the one of the man.
    [Show full text]
  • Evolution of the Tapetum
    UC Davis UC Davis Previously Published Works Title Evolution of the tapetum. Permalink https://escholarship.org/uc/item/3jz996d5 Authors Schwab, Ivan R Yuen, Carlton K Buyukmihci, Nedim C et al. Publication Date 2002 Peer reviewed eScholarship.org Powered by the California Digital Library University of California EVOLUTION OF THE TAPETUM BY Ivan R. Schwab, MD, Carlton K. Yuen, BS (BY INVITATION), Nedim C. Buyukmihci, VMD (BY INVITATION), Thomas N. Blankenship, PhD (BY INVITATION), AND Paul G. Fitzgerald, PhD (BY INVITATION) ABSTRACT Purpose: To review, contrast, and compare current known tapetal mechanisms and review the implications for the evolution of the tapetum. Methods: Ocular specimens of representative fish in key piscine families, including Acipenseridae, Cyprinidae, Chacidae; the reptilian family Crocodylidae; the mammalian family Felidae; and the Lepidopteran family Sphingidae were reviewed and compared histologically. All known varieties of tapeta were examined and classified and compared to the known cladogram representing the evolution of each specific family. Results: Types of tapeta include tapetum cellulosum, tapetum fibrosum, retinal tapetum, invertebrate pigmented tapetum, and invertebrate thin-film tapetum. All but the invertebrate pigmented tapetum were examined histologically. Review of the evolutionary cladogram and comparison with known tapeta suggest that the tapetum evolved in the Devonian period 345 to 395 million years ago. Tapeta developed independently in at least three separate orders in inver- tebrates and vertebrates, and yet all have surprisingly similar mechanisms of light reflection, including thin-film inter- ference, diffusely reflecting tapeta, Mie scattering, Rayleigh scattering, and perhaps orthogonal retroreflection. Conclusion: Tapeta are found in invertebrates and vertebrates and display different physical mechanisms of reflection.
    [Show full text]
  • Corneal Anatomy
    FFCCF! • Mantis Shrimp have 16 cone types- we humans have three- essentially Red Green and Blue receptors. Whereas a dog has 2, a butterfly has 5, the Mantis Shrimp may well see the most color of any animal on earth. Functional Morphology of the Vertebrate Eye Christopher J Murphy DVM, PhD, DACVO Schools of Medicine & Veterinary Medicine University of California, Davis With integrated FFCCFs Why Does Knowing the Functional Morphology Matter? • The diagnosis of ocular disease relies predominantly on physical findings by the clinician (maybe more than any other specialty) • The tools we routinely employ to examine the eye of patients provide us with the ability to resolve fine anatomic detail • Advanced imaging tools such as optical coherence tomography (OCT) provide very fine resolution of structures in the living patient using non invasive techniques and are becoming widespread in application http://dogtime.com/trending/17524-organization-to-provide-free-eye-exams-to-service- • The basis of any diagnosis of “abnormal” is animals-in-may rooted in absolute confidence of owning the knowledge of “normal”. • If you don’t “own” the knowledge of the terminology and normal functional morphology of the eye you will not be able to adequately describe your findings Why Does Knowing the Functional Morphology Matter? • The diagnosis of ocular disease relies predominantly on physical findings by the clinician (maybe more than any other specialty) • The tools we routinely employ to examine the eye of patients provide us with the ability to resolve fine anatomic detail http://www.vet.upenn.edu/about/press-room/press-releases/article/ • Advanced imaging tools such as optical penn-vet-ophthalmologists-offer-free-eye-exams-for-service-dogs coherence tomography (OCT) provide very fine resolution of structures in the living patient using non invasive techniques and are becoming widespread in application • The basis of any diagnosis of “abnormal” is rooted in absolute confidence of owning the http://aibolita.com/eye-diseases/37593-direct-ophthalmoscopy.html knowledge of “normal”.
    [Show full text]
  • Ocular Morphology of the Fruit Bat, Eidolon Helvum, and the Optical Role of the Choroidal Papillae in the Megachiropteran Eye: a Novel Insight
    ONLINE FIRST This is a provisional PDF only. Copyedited and fully formatted version will be made available soon. ISSN: 0015-5659 e-ISSN: 1644-3284 Ocular morphology of the fruit bat, Eidolon helvum, and the optical role of the choroidal papillae in the megachiropteran eye: a novel insight Authors: I. K. Peter-Ajuzie, I. C. Nwaogu, L. O. Majesty-Alukagberie, A. C. Ajaebili, F. A. Farrag, M. A. Kassab, K. Morsy, M. Abumandour DOI: 10.5603/FM.a2021.0072 Article type: Original article Submitted: 2021-06-26 Accepted: 2021-07-08 Published online: 2021-07-21 This article has been peer reviewed and published immediately upon acceptance. It is an open access article, which means that it can be downloaded, printed, and distributed freely, provided the work is properly cited. Articles in "Folia Morphologica" are listed in PubMed. Powered by TCPDF (www.tcpdf.org) Ocular morphology of the fruit bat, Eidolon helvum, and the optical role of the choroidal papillae in the megachiropteran eye: a novel insight I.K. Peter-Ajuzie et al., The megachiropteran eye I.K. Peter-Ajuzie1, I.C. Nwaogu1, L.O. Majesty-Alukagberie2, A.C. Ajaebili1, F.A. Farrag3, M.A. Kassab4, K. Morsy5, 6, M. Abumandour7 1Department of Veterinary Anatomy, Faculty of Veterinary Medicine, University of Nigeria, Nsukka, Enugu State, Nigeria 2Department of Veterinary Public Health and Preventive Medicine, Faculty of Veterinary Medicine, University of Nigeria, Nsukka, Enugu State, Nigeria 3Department of Anatomy and Embryology, Faculty of Veterinary Medicine, Kafrelsheikh University, Kafrelsheikh, Egypt 4Department of Cytology and Histology, Faculty of Veterinary Medicine, Kafrelsheikh University, Kafrelsheikh, Egypt 5Biology Department, College of Science, King Khalid University, Abha, Saudi Arabia 6Zoology Department, Faculty of Science, Cairo University, Cairo, Egypt 7Department of Anatomy and Embryology, Faculty of Veterinary Medicine, Alexandria University, Egypt Address for correspondence: Iheanyi K.
    [Show full text]
  • Evolution of the Tapetum
    EVOLUTION OF THE TAPETUM BY Ivan R. Schwab, MD, Carlton K. Yuen, BS (BY INVITATION), Nedim C. Buyukmihci, VMD (BY INVITATION), Thomas N. Blankenship, PhD (BY INVITATION), AND Paul G. Fitzgerald, PhD (BY INVITATION) ABSTRACT Purpose: To review, contrast, and compare current known tapetal mechanisms and review the implications for the evolution of the tapetum. Methods: Ocular specimens of representative fish in key piscine families, including Acipenseridae, Cyprinidae, Chacidae; the reptilian family Crocodylidae; the mammalian family Felidae; and the Lepidopteran family Sphingidae were reviewed and compared histologically. All known varieties of tapeta were examined and classified and compared to the known cladogram representing the evolution of each specific family. Results: Types of tapeta include tapetum cellulosum, tapetum fibrosum, retinal tapetum, invertebrate pigmented tapetum, and invertebrate thin-film tapetum. All but the invertebrate pigmented tapetum were examined histologically. Review of the evolutionary cladogram and comparison with known tapeta suggest that the tapetum evolved in the Devonian period 345 to 395 million years ago. Tapeta developed independently in at least three separate orders in inver- tebrates and vertebrates, and yet all have surprisingly similar mechanisms of light reflection, including thin-film inter- ference, diffusely reflecting tapeta, Mie scattering, Rayleigh scattering, and perhaps orthogonal retroreflection. Conclusion: Tapeta are found in invertebrates and vertebrates and display different physical mechanisms of reflection. Each tapetum reflects the wavelengths most relevant to the species’ ecological niche. With this work, we have hypothe- sized that the tapetum evolved independently in both invertebrates and vertebrates as early as the Devonian period and coincided with an explosion of life forms.
    [Show full text]
  • The Eyes of Lanternfishes (Myctophidae, Teleostei)
    RESEARCH ARTICLE The Eyes of Lanternfishes (Myctophidae, Teleostei): Novel Ocular Specializations for Vision in Dim Light Fanny de Busserolles,1 N. Justin Marshall,2 and Shaun P. Collin1 1Neuroecology Group, School of Animal Biology and the Oceans Institute, The University of Western Australia, Crawley, Western Australia 6012, Australia 2Sensory Neurobiology Group, Queensland Brain Institute, University of Queensland, St. Lucia, Queensland 4072, Australia Lanternfishes are one of the most abundant groups of mes- region (typically central retina) composed of modified pig- opelagic fishes in the world’s oceans and play a critical role ment epithelial cells, which we hypothesize to be the rem- in biomass vertical turnover. Despite their importance, very nant of a more pronounced visual specialization important little is known about their physiology or how they use their in larval stages. The second specialization is an aggregation sensory systems to survive in the extreme conditions of of extracellular microtubular-like structures found within the deep sea. In this study, we provide a comprehensive the sclerad region of the inner nuclear layer of the retina. description of the general morphology of the myctophid We hypothesize that the marked interspecific differences eye, based on analysis of 53 different species, to under- in the hypertrophy of these microtubular-like structures stand better their visual capabilities. Results confirm that may be related to inherent differences in visual function. A myctophids possess several visual adaptations for dim- general interspecific variability in other parts of the eye is light conditions, including enlarged eyes, an aphakic gap, a also revealed and examined in this study. The contribution tapetum lucidum, and a pure rod retina with high densities of both ecology and phylogeny to the evolution of ocular of long photoreceptors.
    [Show full text]
  • Cow Eye Powerpoint Quiz (Teacher)
    Dissection 101: Cow Eye (Teacher) PowerPoint Quiz Cow Eye Dissection Quiz: Complete the following questions. 1. Name the structure indicated. Cornea 2. What is a function of this structure? Anterior protective covering of the eye; transparent allowing light to enter; continuous with sclera. 3. Name the structure indicated. Optic nerve 4. Name the structure indicated. Retina 5. What is a function of this structure? Nervous tissue, location of the photo receptors (cones for sharp color vision and rods for night, dark/shaded vision); light energy converted to electrical impulse; the retina is continuous with the optic nerve which leaves the back of the eye carrying the nervous impulse to the brain. 6. What is this location called? Optic disc (blind spot) 7. Does the best or worst vision take place at this location? A. Best vision B. Worst vision (circle one) 8. Name the structure indicated. Choroid 9. What is unusual about this structure in the cow in comparison to the human eye? Many vertebrates like the cow, deer and cat have a tapetum lucidum which is an iridescent, reflective layer found on the choroid; the tapetum lucidum aids in the reflection of light, increasing the ability to see at night; the human choroid does not have a tapetum lucidum. 10. Name the structure indicated. Sclera Provided by Dissection 101: Cow Eye PowerPoint Quiz Continue (student) 11. What is a function of this structure? Tough protective outer layer of the eye which gives the eyeball it’s shape; the white part of the human eye; continuous with the transparent cornea.
    [Show full text]