ANATOMY - Eye Flashcards
Which two species have an eyeball with an anterior-posterior compression?
Cattle
Horses
What are the two main segments of the eyeball?
Anterior segment
Posterior segment
Which structure separates the anterior and posterior segments of the eyeball?
Lens
What are the two chambers within the anterior segment of the eyeball?
Anterior chamber
Posterior chamber
What are the boundaries of the anterior chamber in the anterior segment?
The anterior chamber is between the cornea and the iris
What are the boundaries of the posterior chamber of the anterior segment?
The posterior chamber is between the iris and the lens
What is aqueous humor?
Ultra-filtrate of plasma located in the anterior segment of the eyeball
What is vitreous humor?
Gel-like substance located in the posterior segment of the eyeball
What are the three concentric tunics of the eye?
Fibrous tunic
Vascular tunic
Neural tunic (retina)
What are the two functions of the fibrous tunic?
Resists internal pressure
Maintains eyeball shape
What are the two components of the fibrous tunic?
Cornea
Sclera
What is the point of attachment between the cornea and sclera?
Limbus
What allows the cornea to remain transparent?
Organised arrangement of connective tissue fibres and the continual removal of lacrimal fluid
What are the three layers of the cornea?
Epithelium
Substantia propria (connective tissue)
Descemet’s membrane
What is the importance of Descemet’s membrane when using fluorescein to asses corneal ulcers?
Descemet’s membrane does not take up fluorescein so it acts as a protective barrier between the fluorescein and the deeper structures of the eye. This allows the dye to specifically highlight any ulcers in the substantia propria without affecting underlying layers
What are the two main components of the sclera?
Collagen fibres
Elastic fibres
What is the vagina bulba?
Thin membranous covering which separates the sclera from the retrobulbar fat to allow for smooth movement of the eyeball within the orbit
What are the three components of the vascular tunic?
Iris
Choroid
Ciliary body
What is the iris?
The iris is a smooth muscle sphincter that controls the size of the pupil and thus regulates the amount of light that enters the eye
What is the term used for constriction of the pupil?
Miosis
What is the term used for dilation of the pupil?
Mydriasis
What are iridic granules?
Pigmented, roughened prominences present on the pupillary margin of the eye in horses and ruminants
What are the four functions of the ciliary bodies?
Anchors lens
Alter shape of lens through contraction
Produces aqueous humor
Drains aqueous humor
Which disease occurs if aqueous humor fails to drain from the anterior segment of the eyeball?
Glaucoma
What is the choroid?
Vascular tissue running from the optic nerve to the limbus
What is the function of the choroid?
The choroid supplies nutrients to the neural tunic (retina)
Which arteries are found within the choroid?
Ciliary arteries
Which veins are found within the choroid?
Vorticose veins
What is the tapetum lucidum?
Reflective membrane which reflects light back through the retina, increasing the chances of photons stimulating the photoreceptors in the retina to enhance visual sensitivity under low-light conditions
Which species does not have a tapetum lucidum?
Pigs
What are the two divisions of the neural tunic (retina)?
Pars optica retinae
Pars ceca retinae
What is the difference between the pars optica retinae and the pars ceca retinae?
Pars optica retinae is the portion of the neural tunic (retina) which has photoreceptors cells and is involved in light detection however the pars ceca retinae has no photoreceptor cells
What is the optic disc?
The point of entry of cranial nerve II (optic nerve) into the neural tunic (retina)
What are the four adnexal structures of the eye?
Orbit
Extraocular muscles
Palpabrae (eyelids)
Lacrimal apparatus
Which three bones of the skull make up the orbit?
Frontal bone
Lacrimal bone
Zygomatic bone
What are the four rectus extraocular muscles?
Dorsal rectus muscle
Ventral rectus muscle
Medial rectus muscle
Lateral rectus muscle
What are the two oblique extraocular muscles?
Dorsal oblique muscle
Ventral oblique muscle
What is the function of the dorsal oblique muscle?
Rotation of the eye downwards and outwards
What is the function of the ventral oblique muscle?
Rotation of the eye upwards and inwards
Which extraocular muscle can retract the eyeball into the orbit?
Retractor bulbi muscle
What are the two true eyelids?
Upper palpabrae
Lower palpabrae
Where do the upper and lower palpabrae meet?
Commissures
What is the name of the space between the upper and lower palpabrae?
Palpabral fissure
What are the three layers of the palpabrae (eyelids)?
Skin
Musculofibrous layer
Conjunctiva
What are the two skeletal muscles in the musculofibrous layer of the palpabrae (eyelids)?
Obicularis oculi muscle
Levator palpabrae superiosus muscle
What is the fibrous plate within the musculofibrous layer of the palpabrae (eyelids)
Tarsal plate
What is the function of the tarsal glands surrounding the tarsal plate?
Production of the lipid layer of the lacrimal fluid (tears)
What is the name of the space between the palpabrae (eyelids) and the eyeball?
Conjunctival sac
What is the name of the lacrimal gland associated with the third eyelid?
Gland of the third eyelid
What is ‘cherry eye’?
Prolapse of the gland of the third eyelid
What is the function of the lacrimal apparatus?
Production of lacrimal fluid (tears)
What are the two functions of lacrimal fluid (tears)?
Protection of the cornea
Nutrient provision to the cornea
What are the three main glands which make up the lacrimal apparatus?
Lacrimal gland
Gland of the third eyelid
Tarsal glands
Describe the drainage root for lacrimal fluid (tears)?
Lacrimal fluid is drained into slits adjacent to the lacrimal caruncle (tear duct) known as puncta lacrimalia which drain into the lacrimal sac followed by the nasolacrimal duct and into the nasal vestibule
What are the three layers of the lacrimal fluid (tears)?
Lipid layer
Mucin layer
Aqueous layer
What produces the mucin layer of lacrimal fluid (tears)?
Conjunctival goblet cells
What is the main artery supplying the eye?
External ophthalmic artery
Which six cranial nerves innervate the eye?
Cranial nerves II to VII
