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