EVALUATION OF THE DEVELOPMENTAL MORPHOLOGY OF THE EYEBALL OF THE RED SOKOTO GOAT (Capra hircus) A DISSERTATION SUBMITTED TO THE SCHOOL OF POSTGRADUATE STUDIES OF THE UNIVERSITY OF NIGERIA IN PARTIAL FULFILLMENT FOR THE AWARD OF THE DEGREE OF MASTER OF SCIENCE IN VETERINARY ANATOMY BY NLEBEDUM, U.C. (PG/M.Sc./07/48006) DEPARTMENT OF VETERINARY ANATOMY FACULTY OF VETERINARY MEDICINE UNIVERSITY OF NIGERIA, NSUKKA. JANUARY, 2015. i CERTIFICATION This is to certify that this project was carried out by NLEBEDUM UCHENNA. C. in the Department of Veterinary Anatomy, University of Nigeria, Nsukka. The work is original and has not been submitted either wholly or in part for the award of any degree or diploma of this University or any other University. It is submitted in partial fulfillment for the award of Master of Science degree of the University of Nigeria, Nsukka. ------------------------------------------ ---------------------------------------- Prof. D.N. Ezeasor Prof. I.C. Nwaogu (Supervisor) (Head of Department) -------------------------------------------- ---------------------------------------- Prof. B.I. Onyeanusi Prof. C.O Nwosu (External Examiner) (Dean of Faculty) ii DEDICATION To my loving wife, best friend and “sister”- Ugoma; Daddy, Mummy, Obi and Nomso my other “sister” iii ACKNOWLEDGEMENT Glory and honour to almighty God for His love, protection and sustenance. I am indebted to my supervisor, Prof. D.N Ezeasor, for his patient guidance and painstaking corrections which has opened the wide doors of scientific research to me. I wish to sincerely thank Prof. Nwaogu, I.C., Dr. Igbokwe, C.O., Dr. Okpe, G.C., Dr. Igwebuike, U.M., Dr. Udoumoh, A and Dr. Abiaezute, C.N. for their invaluable assistance. I am also very grateful to the head of department and staff of department of Veterinary Anatomy, Michael Okpara University of Agriculture, Umudike especially Mr. Agbakwuru, I.O for his invaluable technical assistance. My appreciation goes to my friends and colleagues; Drs. Nnadozie, O., Okafor, C., Onoja, B., Ibe, C.S and Ezeja, M. and also to Dr. Ikpegbu, E., for his immeasurable support and assistance. I deeply appreciate the support and sacrifice of my family during the course of this work. I will remain grateful to you all. NLEBEDUM, U.C January, 2015. iv TABLE OF CONTENTS TITLE PAGE---------------------------------------------------------------------------------------------i CERTIFICATION--------------------------------------------------------------------------------------ii DEDICATION------------------------------------------------------------------------------------------iii ACKNOWLEDGEMENT----------------------------------------------------------------------------iv TABLE OF CONTENTS------------------------------------------------------------------------------v SUMMARY----------------------------------------------------------------------------------------------xi CHAPTER ONE ………………………………………………………………….. 1 1.1 INTRODUCTION ……………………….…………………………….…...1 1.2 STATEMENT OF PROBLEM .………...…………….…………….….….2 1.3 MAIN RESEARCH OBJECTIVE ……………………………….….…….3 1.4 SPECIFIC OBJECTIVES ………………………………………….………3 CHAPTER TWO ………………………………………………………………...…4 LITERATURE REVIEW …………………………………………………………..4 2.1 EMBRYOLOGY OF THE EYEBALL …………………………………....4 2.1.1 Development of the cornea ……………………………………….....5 2.1.2 Development of the sclera ………………………………………......6 2.1.3 Development of the choroid ………………………………………...6 2.1.4 Development of the iris and ciliary body …………………………..6 2.1.5 Development of the lens ……………………………………….….....7 2.1.6 Development of the retina ………………………………………......7 2.1.7 Development of the optic nerve …………………………………….8 2.2 GROSS ANATOMY OF THE EYEBALL ………………………………...8 2.2.1 OUTER FIBROUS TUNIC ……………………………………..…10 2.2.1.1 Cornea ……………………………………………………………….10 2.2.1.2 Sclera ………………………………………………………………...11 2.2.2 MIDDLE VASCULAR TUNIC …………………………………….12 v 2.2.2.1 Iris …………………………………………………………………….13 2.2.2.2 Ciliary body ………………………………………………………….14 2.2.2.3 Choroid ………………………………………………………………16 2.2.3 INNER NERVOUS LAYER ………………………………………..17 2.2.3.1 Retina ……………………………………………………………...…17 2.2.4 OPTIC NERVE ……………………………………………………..18 2.2.5 LENS ……………………………………………………………...…18 2.3 HISTOLOGY OF THE EYEBALL ……………………………………….19 2.3.1 OUTER FIBROUS TUNIC ………………………………………..19 2.3.1.1 Cornea ………………………………………………………………19 2.3.1.2 Sclera ………………………………………………………………..21 2.3.2 VASCULAR LAYER ………………………………………………22 2.3.2.1 Iris …………………………………………………………………...23 2.3.2.2 Ciliary body ………………………………………………………...24 2.3.2.3 Choroid ……………………………………………………………..25 2.3.2.4 Tapetum lucidum …………………………………………………..26 2.3.2.5 Choriocapillaris …………………………………………………….27 2.3.3 NERVOUS TUNIC ………………………………………………...28 2.3.3.1 Retina ……………………………………………………………….28 2.3.3.1.1 Retinal Pigment Epithelium (RPE) ……………………………….28 2.3.3.1.2 Layer of rods and cones …………………………………………...29 2.3.3.1.3 External Limiting Membrane …………………………………….30 2.3.3.1.4 Outer Nuclear Layer ………………………………………………30 2.3.3.1.5 Outer Plexiform Layer …………………………………………....30 2.3.3.1.6 Inner Nuclear Layer ……………………………………………….31 2.3.3.1.7 Inner Plexiform Layer …………………………………………….33 2.3.3.1.8 Ganglion Cell Layer ……………………………………………….33 2.3.3.1.9 Nerve Fiber Layer ………………………………………………....34 2.3.3.1.10 Inner Limiting Membrane ………………………………………...34 2.3.4 Optic Nerve …………………………………………………………34 vi 2.3.5 LENS ………………………………………………………………..34 CHAPTER THREE ………………………………………………………………..37 MATERIALS AND METHODS ………………………………………………….37 3.1 ACQUISITION OF SPECIMEN ………………………………....37 3.2 AGEING …………………………………………………………....37 3.3 TISSUE PREPARATION …………………………………………37 3.4 PHOTOMICROGRAPHY …………………………………….….38 3.5 HISTOMORPHOMETERY ……………………………………...38 3.6 STATISTICS ……………………………………………………….38 CHAPTER FOUR ………………………………………………………………….39 RESULTS …………………………………………………………………………...39 4.1 FETUSES OF ABOUT 45 DAYS ……………………………………….…39 4.1.1 FIBROUS TUNIC …………………………………………….....…39 4.1.1.1 Cornea ……………………………………….………………………39 4.1.2 VASCULAR TUNIC ……………………………………………....39 4.1.2.1 Iris ……………………………………………………………….….39 4.1.2.2 Choroid ………………………………………………………….….40 4.1.3 NERVOUS TUNIC …………………………………………….…40 4.1.3.1 Retina …………………………………………………………....…40 4.1.4 LENS ……………………………………………………………….41 4.2 FETUSES OF ABOUT 59 DAYS ………………………………………...42 4.2.1 FIBROUS TUNIC …………………………………………………42 4.2.1.1 Cornea ……………………………………………………………...42 4.2.1.2 Sclera ……………………………………………………………….42 4.2.2 VASCULAR TUNIC. …………………………………………….43 4.2.2.1 Iris ………………………………………………………………….43 4.2.2.2 Ciliary body ……………………………………………………….43 4.2.2.3 Choroid ……………………………………………………………44 4.2.3 NERVOUS TUNIC ………………………………………………45 4.2.3.1 Retina ……………………………………………………………...45 vii 4.2.4 OPTIC NERVE …………………………………………………....45 4.2.5 LENS …………………………………………………………….…45 4.3 FETUSES OF ABOUT 75 DAYS ……………………………………..….46 4.3.1 FIBROUS TUNIC ………………………………………………....46 4.3.1.1 Cornea …………………………………………………………..….46 4.3.1.2 Lamina cribrosa …………………………………………………...47 4.3.2 VASCULAR TUNIC ……………………………………………....47 4.3.2.1 Iris …………………………………………………………………..47 4.3.2.2 Ciliary body ………………………………………………………...47 4.3.2.3 Choroid ……………………………………………………………..48 4.3.3 NERVOUS TUNIC …………………………………………………48 4.3.3.1 Retina ………………………………………………………………..48 4.3.4 THE LENS ………………………………………………………….49 4.4 FETUSES OF ABOUT 105 DAYS ………………………………………..49 4.4.1 FIBROUS TUNIC ………………………………………………….49 4.4.1.1 Cornea ………………………………………………………………49 4.4.1.2 Sclera ………………………………………………………………..50 4.4.2 VASCULAR TUNIC ……………………………………………….50 4.4.2.1 Iris …………………………………………………………………...50 4.4.2.2 Ciliary body …………………………………………………………51 4.4.2.3 Choroid ……………………………………………………………...52 4.4.3 NERVOUS TUNIC …………………………………………………52 4.4.3.1 Retina ………………………………………………………………..52 4.4.4 OPTIC NERVE ……………………………………………………..53 4.4.5 LENS ………………………………………………………………...53 4.5 NEONATE …………………………………………………………………..54 4.5.1 FIBROUS TUNIC …………………………………………………..54 4.5.1.1 Cornea ……………………………………………………………….54 4.5.1.2 Limbus ………………………………………………………………55 4.5.1.3 Sclera ………………………………………………………………..55 viii 4.5.1.4 Lamina cribrosa ……………………………………………………55 4.5.2 VASCULAR TUNIC ………………………………………………56 4.5.2.1 Iris …………………………………………………………………..56 4.5.2.2 Ciliary body ………………………………………………………...57 4.5.2.3 Choroid ……………………………………………………………..57 4.5.3 NERVOUS TUNIC ………………………………………………...58 4.5.3.1 Retina ……………………………………………………………….58 4.5.4 OPTIC NERVE …………………………………………………….61 4.5.5 LENS ………………………………………………………………...61 4.6 ADULT ……………………………………………………………………..62 4.6.1 FIBROUS TUNIC ………………………………………………….62 4.6.1.1 Cornea ………………………………………………………………62 4.6.1.2 Limbus ………………………………………………………………63 4.6.1.3 Sclera ………………………………………………………………..63 4.6.1.4 Lamina cribrosa ……………………………………………………64 4.6.2 VASCULAR TUNIC ………………………………………………64 4.6.2.1 Iris …………………………………………………………………..64 4.6.2.2 Ciliary body ………………………………………………………..65 4.6.2.3 Choroid …………………………………………………………….67 4.6.3 NERVOUS TUNIC ………………………………………………..67 4.6.3.1 Retina ……………………………………………………………….67 4.6.4 OPTIC NERVE HEAD …………………………………………....70 4.6.5 LENS ………………………………………………………………..71 FIGURES …………………………………………………………………..72 CHAPTER FIVE …………………………………………………………………..143 DISCUSSION ………………………………………………………………………143 5.1 OUTER FIBROUS LAYER ……………………………………………….144 5.1.1 Cornea ………………………………………………………………144 5.1.2 Sclera ………………………………………………………………..148 5.1.3 Lamina Cribrosa …………………………………………………...148 ix 5.2 MIDDLE VASCULAR COAT …………………………………………….149 5.2.1 Iris …………………………………………………………………...149 5.2.2 Ciliary Body …………………………………………………………151 5.2.3 Choroid ……………………………………………………………...154 5.3 INNER NERVOUS COAT ……………………………………………....…157 5.4 LENS ………………………………………………………………...163 REFERENCES ………………………………………………………………....…..167 x ABSTRACT