Special Senses (final)

Ocular

Relating to the eye

Aural

Relating to the ear

Tapetum Lucidum

Reflects light in the eye

Anterior Chamber

Chamber between the cornea and iris, contains aqueous humor (watery)

Posterior Chamber

Chamber between the iris and lens, contains aqueous humor (watery)

Vitreous Chamber

Chamber between the lens and retina, contains vitreous humor (gelatinous)

Aqueous Humor

Produced at ciliary body and exits at the iridocorneal angle

Cornea

Anterior third of the fibrous tunic surrounding the eye; transparent due to avascularity (nutrition from tear film and aqueous humor), dehydration, and parallel collagen organization

Corneal Epithelium

Epithelial cells forming the outer layer of the cornea

Corneal Stroma

Composed of parallel collagen fibers

Descemet's Membrane

Cell-free membrane

Corneal Endothelium

Maintains water balance in the stroma

Corneal Edema

Fluid in the cornea with a blue appearance

Corneal Scarring

White scar tissue in the cornea

Neovascularization

Red linear blood vessels form in the cornea

Corneal Pigmentation

Brown/black melanin pigment in the cornea

Keratitis

Inflammation of the cornea that appears yellow or creamy

Mineral Deposits

Calcium deposits in the cornea that appears white and crystalline

Corneal Erosion

Partial thickness loss of epithelium

Corneal Ulceration

Full thickness loss of epithelium and some stromal loss; presents with corneal edema, neovascularization, and green exposed stroma on Fluorescein stain; caused by trauma, exposure, infection, or keratoconjunctivitis sicca

Descemetocele

Full thickness loss through the stroma, leaving only Descemet's membrane intact

Corneal Perforation

Full thickness loss of the cornea with exposure of the anterior chamber

Keratoconjunctivitis Sicca

Dry eye, decreased production of tear film common in dogs, diagnosed with Schirmer Tear Test; can lead to corneal ulceration (acute) or epidermalization (chronic)

Infectious Bovine Keratoconjunctivitis

Pink eye, caused by Moraxella spp. bacteria; highly contagious and appears with intense inflammatory cell infiltrates

Uveal Tract

Vascular and pigmented tunic of the eye; iris, ciliary body, and choroid

Uveitis

Inflammation of the uveal tract; neutrophils and macrophages settle in eye chambers while lymphocytes and plasma cells remain in tissues near vessels

Hypopion

Neutrophils settle in anterior chamber, seen in uveitis

Retina

Light-sensitive layer at the back of the eye; transduces visible light into neural impulses to be transmitted to the visual cortex of the brain

Neurosensory Retina

8 layers of neurons and axons + 1 layer of photoreceptors

Retinal Pigment Epithelium

Outermost layer of the retina

Rods

High sensitivity, low acuity, no color

Cones

Low sensitivity, high acuity, color

Retinal Detachment

Separation of neurosensory retina from RPE; can be partial (localized) or complete (retina billows into vitreous); shows exudate in space under detached retina and tombstoning on necropsy (must differentiate from artifact)

Glaucoma

Elevated intraocular pressure due to blockage of aqueous fluid outflow at the iridocorneal angle (production is normal); can cause retinal atrophy and cupping of the optic nerve

Ear

Transduces sound waves into the brain and manages the vestibular system

External Ear

Pinna, external auditory meatus, and ceruminous glands (produce ear wax)

Middle Ear

Tympanic membrane (eardrum responding to sound waves), tympanic cavity, tympanic bulla (ventral), and auditory ossicles (3 bone chain)

Inner Ear

Cochlea and vestibular system (semicircular canals)

Cochlea

Membranous and bony labyrinths that transform mechanical deflection of fluid waves into neurologic impulses

Otitis

Inflammation of the ear

Otitis Externa

Bacteria and fungi enter via extension from the environment and can spread to middle/inner ear; predisposed by external ear moisture; chronic infection causes itch and thickening of epidermis

Otitis Media

Pathogens enter via extension through tympanic membrane or ascension of auditory tube; can cause (or result from) tympanic membrane rupture; causes lysis/erosion of surrounding bone and facial nerve paralysis

Otitis Interna

Pathogens enter via extension from middle ear; associated with neurologic deficits