EYEBALL REVIEW QUESTIONS Ross University School of Veterinary Medicine Histology November 2003 Amy Fayette
What is the tear pathway? Lacrimal puncta Lacrimal canaliculi Lacrimal sac Nasolacrimal duct Nasal cavity
What makes up the aqueous portion of tears? Lacrimal gland Gland of 3 rd eyelid
What type of tapetum lucidum does a dog have? cellular
What are the corneal layers? Anterior corneal epithelium Subepithelial basement membrane Stroma Descemets membrane Posterior corneal epithelium
What makes up the nervous tunic of the eye? Retina –Optical part –Ciliary part –Iridal part
Where are tears drained? Medial canthus via puncta
What makes up the vascular tunic of the eye? Iris Ciliary body and process choroid
Where does the retina arrive from during development? Neuroectoderm –diencephalon
What is the function and composition of the vitreous body? 99% water, some hyaluronic acid Gel cortex, liquid center Aids in maintaining shape and retinal apposition
What is the function of the tapetum lucidum? Reflects light, providing additional stimulus to the photoreceptor cells in low light
What makes up the fibrous tunic of the eye? Sclera and cornea
What type of tapetum lucidum does a cow have? fibrous
What is the function of the iris? Controls the amount of light admitted Pigment and eye color
What produces the oily portion of tears? MMeibomian glands
Embryologically which parts of the eye are derived from the ectoderm? Lens Palpebral Anterior corneal epithelium
What are the ten layers of the optical retina and what do they contain? PPigmented epithelium RRods and cones (process of photoreceptor cells) EExternal limiting membrane (cytoplasm of muller cells) EExternal nuclear layer (nuclei of photoreceptor cells) EExternal plexiform layer (axons and dendrites) IInternal nuclear layer (nuclei of bipolar cells) IInternal plexiform layer (axons and dendrites) GGanglion cell layer NNerve fiber layer (axons from ganglion cells) IInternal limiting membrane (cytoplasm of muller cells)
What are the two muscles associated with the iris and what is their innervation? Sphincter pupillae m. = parasympathetic Dilator pupillae m. = sympathetic
What are rods and what pigment do they utilize? Low light sensitivity Pigment = rhodopsin Vitamin A important
What is the adnexa? Palpebrae Glands
What is meant by the “lens bow”? The anterior lens epithelial cells elongate to form lens fibers
Embryologically which parts of the eye are derived from mesoderm? Sclera Choroid Extraocular muscles Ciliary muscles Stroma
What is the conjunctiva? Mucous membrane on innersurface of papebrae extending to the limbus of the cornea –Palpebral and bulbar conjunctivae Stratified squamous epithelium Goblet cells present in palpebral conjunctiva
What produces the mucous portion of tears? Mucous glands
What is aqueous humor and what is a disease process associated with it? Aqueous solution occupying the anterior and posterior chambers Formed by ciliary epithelium Nourishes cornea, maintains intraocular pressure and some ocular shape Glaucoma
What are cones and what pigment do they utilize? Visual acuity and color perception Pigment = iodopsin
What does miosis and mydriasis mean? MMiosis = constriction MMydriasis = dilation
What attaches the lens to the ciliary body? Zonule fibers
What are the two main functions of the coroid? Contains nutrient blood supply to majority of retina Contains tapetum lucidum
What is the drainage pathway of aqueous humor? Posterior chamber Pupil Anterior chamber Iridocorneal angle Scleral venous plexus of systemic circulation