Ocular Anatomy Flashcards
Obj: Innervation of extraocular muscles
- Oculomotor (CN III)
- Trochlear (CN IV)
- Abducens (CN VI)
Obj: Purpose of tapetum
Allows for second stimulation of photoreceptors - increases low-light vision
Obj: Vascular patterns in the retina
- Holangiotic Vascular Pattern
- Merangotic Pattern
- Paurangiotic
- Anangiotic
What are the medical abbreviations for the eyes?
- OD - Oculus dexter
- Right eye
- OS - Oculus sinister
- Left eye
- OU - Oculi uterque
- Both eyes
What animals have an enclosed orbit?
- Cows, sheep, horses, goats, and primates
What type of orbit are seen in pigs & carnivores?
- Incomplete or Open
- Supraorbital ligament connects frontal and zygomatic bones
What structures can have effects on the Orbit?
- Bones - breaks, malunion
- Sinuses- frontal and maxillary
- Ramus of the Mandible
- Foramina
- Muscles of mastication - inflammation
- Teeth - upper 4th premolar - root abscess
What is the innervation of the Extraocular Muscles?
- Oculomotor (CN III)
- dorsal (superior) rectus
- Ventral (inferior) rectus
- medial rectus
- ventral (inferior) oblique muscles
- Trochlear (CN IV)
- Dorsal (superior) oblique muscles
- Abducens (CN VI)
- Retractor bulbi muscle
- lateral rectus
What do the rectus muscles of the eye do?
- Rotate globe in the direction of their name
- Dorsal (superior) rectus
- Ventral (inferior) rectus
- Medial rectus
- Lateral rectus
What are the functions of the Oblique muscles of the eye?
- Dorsal (superior) oblique muscle - intorsion of the globe
- Ventral (inferior) oblique muscle - extorsion of the globe
What are the components of the Eyelid?
- Skin
- Cilia
- Subcutaneous CT
Muscles - Meibomian glands
- Conjunctiva
What is the function of the Eyelids?
- Corneal protection
- Production, distribution, and drainage of tear film
What are the muscles of the Eyelid? innervation? Function?
- Levator palpebrae superioris muscle
- innervated by CN III
- Elevates upper eyelid
- Obicularis oculi Muscle
- Innervated by CN VII
- Blink
- Mueller’s muscle
- smooth muscle
- Sympathetic tone
- Widens palpebral fissure
- Elevates upper eyelid
- Depresses lower eyelid
- Horner’s syndrome loss of sympathetic innervation
What are the glands are part of the orbit?
- Orbital Lacrimal Gland
- ~60 - 70% of aqueous tear fluid
- Superior-temporal orbit
- Gland of the 3rd eyelid
- Base of 3rd eyelid
- ~30 - 40% of aqueous tear fluid
What is Conjunctiva?
- Mucus membrane
- Palpebral conjunctiva
- Lines inner surface of eyelids
- Bulbar conjunctiva
- Covers surface of globe
- Nictitans membrane
- Conjunctival fornices
- loose soft tissue where the bulbar and palpebral conjunctiva meet
What are the layers of the eye?
- Fibrous tunic
- Cornea
- Sclera
- Vascular Tunic
- Anterior uvea
- Iris
- Ciliary body
- Posterior uvea
- Choriod
- Anterior uvea
- Neural tunic
- Retina
What are the layers of the Cornea
- Epithelium
- Stroma
- Descemet’s membrane
- Endothelium
describe the cornea
- Richly innervated
- sensory nerves
- pain receptors from long ciliary nerve
- ophthalmic division of CN V)
- Superficial cornea more innervated with pain receptors
- Varies with age, species, skull shape, systemic disease
- Optical clarity
- No pigment or blood vessels
- Non-myelinated nerve fibers
- Relatively dehydrated
- Arrangement of collagen fibrils
- Thickness: <1mm
- Varies by species and location
- Central cornea thinnest
- Peripheral cornea thickest
Describe the corneal epithelium
- Nonkeratinized stratified squamous epithelium
- 25-40 um in dogs, cats
- 2 - 4x thicker in horses, cattle
- Lipophilic
- Barrier to drugs
Describe the Descemet’s membrane
- BM of corneal endothelium
- Lipophilic
- does not retain fluorescein
Describe the endothelium of the cornea
- Single layer of flattened cells
- Poor regenerative ability
- Na+/K+ ATPase pump removes fluid from stroma
- Cornea relatively dehydrated
- 75 - 85% water
Describe the structure of the Sclera
- Limbus
- corneoscleral junction
- variably pigmented
- Lamina cribosa
- optic nerve passes through sclera
- Thickness varies considerably
- thinnest near equator (0.12mm dog)
What are the structures of the Uveal Tract
- Anterior uvea
- Iris
- Ciliary body
- Posterior Uvea
- Choroid
- tapetum
- Choroid
What are the muscles of the iris?
- Iris sphincter muscle (pink)
- Iris dilator muscle (purple)
- smooth muscle - mammals
- striated muscle - birds/reptiles
What type of innervation does the iris have?
- Parasympathetic
- Sympathetis
What is the Ciliary Body?
- Pars plicata
- production of aqueous humor by nonpigmented ciliary body epithelium
- Pars plana
- Zonules
- attach ciliary body process to the equator of the lens
- Ciliary body muscle
- Accommodation
What is the Conventional outflow pathway of Aqueous Humor?
- Ciliary body epithelium
- Posterior chamber
- Pupil
- Anterior chamber
- Iridocorneal angle
- Vortex veins
- Systemic circulation
What is the unconventional outflow pathway of Aqueous Humor Outflow?
- Uveoscleropathway
- Iris Stroma
- Ciliary body stroma
- Supraciliary-suprachoroidal space
- Sclera
- Systemic circulation
What is the Posterior Uvea composed of?
- Choroid
- Comprised primarily of blood vessels
- Choriocapillaris
- Main source of nutrition for outer layers of retina
- Tapetum
- Large vessel layer
What is the tapetum lucidum?
- Reflective layer in the inner choroid
- located in the Dorsal Fundus
- Allows second stimulation of photoreceptors
What animals do NOT have a tapetum lucidum?
- Humans
- red kangaroo
- squirrels
- llamas / alpacas
- pigs
What is the Retina made up of? what does it do?
- Rods and cones
- Rods = dim light
- shapes and motion
- Cones = daylight
- color vision
- visual acuity
- Rods = dim light
- Area centralis - area of high cone density in domestic animals
- Fovea-primates - cone-rich area in some birds/reptiles
- Potential space between Retinal Pigment Epithelium and Photoreceptors
- Retinal detachments
- Retina is firmly attached
- optic nerve head
- Ora ciliaris retinae
name this vascular pattern
Holangiotic Vascular Pattern
Name this vascular pattern
Merangiotic Pattern
name this vascular pattern
Paurangiotic Vascular Pattern
Name this vascular pattern?
Anangiotic Vascular pattern
What are the structures of the Lens
- Lens capsule
- Canine anterior lens capsule 50-70 um
- Canine posterior lens capsule 2-4 um
- Anterior epithelium
- Lens fibers
- Equator
- Nucleus
- Cortex
What is Vitreous Humor?
- Occupies up to ⅔ volume of the globe
- Transparent, jelly-like material
- ~99% water, collagen, hyaluronic acid
- Functions:
- Transmit light
- Maintain the normal retinal position
What is the Optic Nerve
- Retinal ganglion cell axons leave nerve fiber layer and form the optic nerve
- Pass through the optic chiasm
- Nerves cross over (Decussation)
What is the Optic Nerve
- Retinal ganglion cell axons leave nerve fiber layer and form the optic nerve
- Pass through the optic chiasm
- Nerves cross over (Decussation)
