Anatomy of Eye/Adnexa
Lacrimal caruncle
"Lump" in the lacrimal lake Make bear fine hairs in large animals
Range of mammal electromagnetic energy picked up by vision
400-700 nm
Lacrimal lake
Accumulation of tear fluid near medial canthus
Describe directional terms for eye
Anterior (rostral) Posterior (caudal) Superior (dorsal) Inferior (ventral)
Injury to pterygopalatine fossa can cause damage to what CNS
CNII (optic) CNs in orbital fissure (Occulomotor, Trochlear, Ophthalmic, Abducens) CNs is rostral alar foramen (V2/Maxillary)
What is the levator palpebrae superioris innervated by
CNIII (Occulomotor)
The palpebral nn is a terminal branch of what CN? What mm does it supply?
CNVII/Facial Supplies orbicularis oculi
Compare carnivores vs herbivores placement/appearance of bony orbits in skull
Carnivores: orbit more rostral (more binocular/less peripheral vision). Incomplete orbit (completed by orbital ligament) Herbivores: orbit more lateral (less binocular/more peripheral). Complete orbit
Describe structure/location of the nictitating membrane
Cartilage (often T-shaped) supported by connective tissue that is anchored in the medial canthus (Carried across anterior globe like a windshield wiper)
Name for eyelashes
Cilia
Purpose of duct system
Conducts tears from medial canthus into vestibule for evaporation there
The nictitating membrane is held in retraction by ___? Describe innervation. Clinical significance?
Contraction of the orbitalis (smooth/involuntary) muscle which is under sympathetic control This sympathetic control is lost/disrupted during Horner's Syndrome cases, which is why we see protrusion of 3rd eyelid
Do cats have cilia
Controversial/generally accepted that they have tiny eyelids hidden in rest of fur
Pupillary constrictor vs dilator: which is parasympathetic s sympathetically innervated
Dilator: sympathetic Constrictor: parasympathetic
Compare dog vs horse vs ruminant cilia
Dogs: only upper cilia Horses/ruminants: upper and lower cilia
CNIII simultaneously contracting the L.P.S along with what other mm ensure that when globe (eye) rotates upward, upper eyelid is also raised
Dorsal rectus mm
In the lacrimal apparatus, describe path/direction of tears after they exit the eye
Exit of tears is through medial canthus to nasal vestibule via nasolacrimal duct system Tears generally flow dorsolateral to ventromedial
Primary artery supplying eye? This is a branch of what vessel? Path?
External ophthalmic artery (branch of maxillary artery passing through rostral alar foramen)
Name for eyelids
Eyelids = palebrae (singular is palpebrum) Superior and inferior palpebrum (eyelids)
The nasolacrimal duct: Is fusion of __ Purpose? Empties into __
Fusion of the 2 lacrimal canaliculi Provides evaporative space Empties into nasal vestibule
What spp has a more prominent supraorbital fossa/depression? Clinical significance?
Horses Moves up and down when horses chew/one of last fat structures to degrade in starvation/cachexia
Know location/structures in pterygopalatine fossa
Houses globe and adnexa and multiple foramina (orbital fissure, alar foramen, etc)
Purpose of medial/lateral palpebral ligaments
Ligaments anchor eyelids medially and laterally so they close in horizontal line when orbicularis oculi mm contract
What is the name for the edges/corners of eyes where the 2 lids meet
Medial and lateral canthus (plural is canthi)
Both (dorsal and ventral) of the extraoccular oblique mms start at the __ and after taking their oblique courses, the insert ___
Medially in pterygopalatine fossa Both insert at the respective (dorsal or ventral) lateral aspect of the globe
Describe motion of the nictitating membrane
Motion over eye is passive/slides over globe when eye is retracted into orbit (closed)
Describe the levator palpebrae superioris (L.P.S)
Narrow strip of mm running longitudinally (vert) into upper eyelid (contraction raises the upper lid)
The 2 lacrimal caniculi fuse to form the __ In some cases, __ is present at the fusion site
Nasolacrimal duct; Enlargement called the lacrimal sac
The nasolacrimal duct ends at the __
Nasolacrimal orifice
Name for 3rd eyelid
Nictitating membrane/membrana nictitans
List eye motor nns
Occulomotor Trochlear Abducens Palpebral
List the extra ocular mms innervated by each CN: Occulomotor Trochlear Abducens
Occulomotor: dorsal, ventral, medial rectus, ventral oblique, pupillary sphincter Trochlear: dorsal oblique Abducens: lateral rectus and retractor bulbi
What is the lacrimal puncta/punctum? Spp variation?
One tiny duct opening at medial most margin of superior and inferior lid (Pigs only have superior)
Muscle that closes eyelids/sphincter? Muscle that opens upper eyelid?
Orbicularis oculi Levator palpebrae superioris
Describe position of lacrimal gland? How are tears distributed?
Positioned dorsolaterally within orbit Blinking distributes secretion/tears across globe ventromedially towards medial canthus
What eye structures are parasympathetically innervated
Pupillary constrictor Ciliary body (acts on lens) (Occulomotor innervation)
What eye structures are sympathetically innervated
Pupillary dilator Orbitalis mm (smooth mm keeps globe anteriorly placed in orbit/affected in Horner's syndrome)
Describe shape/path of the retractor bulbi. Isolated action?
Radiates out as cone surrounding Optic nn and attaches to posterior globe in circle Contraction retracts globe deeper into orbit and protrudes 3rd eyelid
Purpose of the dorsal rectus mm by itself
Rotates eye upward
List the tear-producing glands within the lacrimal apparatus
Scattered/small accessory glands within eyelids (hard to see/identify) Gland(s) of the 3rd eyelid Lacrimal gland
What is the interpalpebral fissure (or palpebral fissure)
Space between 2 eyelids when eye is at least partially open
Regarding the Supraorbital fossa: Describe location It is an extension of ___ What structure extends into this space
Space dorsal and caudal to orbit Extension of retrobulbar fat bad Coronoid process of mandible extends in this space
Describe the optic nn/CNII regarding: Purpose? Provided with what covering?
Special sensory to light-sensitive cells of retina (rods/cones) Provided with meninges covering at level of optic papilla/disc to brain (optic nn is a direct outgrowth of brain)
What is adnexa of the eye?
Structures associated with movement, protection and support of the eye (eyelids, conjunctival sac, lacrimal glands etc. NOT eye and optic nn)
What is the bulbar surface
Surface of nictitating membrane on side of globe (inner) Contained lymphoid (lymphatic) tissue
Components of the lacrimal apparatus
Tear-producing glands Duct system
Describe the ventral/inferior oblique mm regarding: Its tendon inserts on what directional side of the globe Isolated action
Tendon passes laterally to insert on ventrolateral globe; Rotates dorsal side of globe laterally
What is the lacrimal canaliculi
Tiny ducts (one from each superior and inferior punctum) leading medially from each punctum
Describe the dorsal/superior oblique mm regarding: It turns around the ___ Its tendon inserts on what directional side of the globe Isolated action
Trochlea (U-shaped cartilage on dorsomedial orbit); Dorsolateral; Rotates dorsal part of globe medially
Sensory innervation to upper vs lower eyelid
Upper eyelid: ophthalmic/V1 Lower eyelid: maxillary/V2