4. Ear, Eye, and Superficial Head Lecture
Trochlea
- A pulley-shaped cartilage that is attached to the dorsomedial wall of the orbit - Directs the course of the dorsal oblique muscle -6 & 6'
superficial gland of the third eyelid
- Accessory lacrimal gland (mucous and serous secretions) - Surrounds cartilage "stem" - Deep gland also in cattle and swine (4')
Choroid
- Black areas for light absorption - Tapetum lucidum (1)
ciliary body
- Ciliary mm. and ciliary ligaments control the shape of the lens (3)
Iris
- Circular and radial mm. regulate the size of the pupil
Orbit
- Composition: • Bones • Orbital ligament - Periorbita
Pupillary muscles
- Constrictor pupillae (circular) • Regulated by the oculomotor nerve (PSNS) - Dilator pupillae (linear, radial) • Regulated by the SNS (neuron processes from cranial cervical ganglion)
Aqueous humor
- Continuously produced and reabsorbed - Secreted by ciliary body epithelium (4) - Drained via the venous sinuses (6) of the sclera at the iridocorneal angle - Increased fluid results in increased intraocular pressure (glaucoma)
Tympanic bulla
- Divided in the cat
There are two curved (oblique) muscles of the globe
- Dorsal oblique (6) - Ventral oblique (5)
Muscles of the globe (eye)
- Dorsal rectus - Ventral rectus - Lateral rectus - Medial rectus - Dorsal oblique - Ventral oblique - Retractor bulbi
There are four straight (rectus) muscles of the globe
- Dorsal rectus (1) - Ventral rectus (3) - Lateral rectus (2) - Medial rectus (4)
Eyeball
- External features - Intraocular structures
Ocular adnexa
- Eyelids (palpebrae) - Conjunctiva - Lacrimal apparatus - Extraocular mm. - Nerves and blood vessels - Trochlea
Muscles of the eyelids (palpebrae)
- Levator palpebrae superioris - Orbicularis oculi - Retractor anguli oculi lateralis - Levator anguli oculi medialis
Palpebral conjunctiva
- Lines the internal surface of the palpebrae - Is continuous with the outer skin of the palpebrae (9) and with the bulbar conjunctiva at the fornix (12) - The third eyelid (21) is a fold of the inferior palpebral conjunctiva
Anterior compartment
- Located between the lens and cornea - Filled with aqueous humor - Divided by the iris (1) into two chambers: anterior chamber and posterior chamber
Posterior compartment
- Located between the lens and fundus - Contains the vitreous body
Auditory tube
- Opens distally into the nasopharynx = pharyngeal opening of the auditory tube
Bulbar conjunctiva
- Reflects onto the surface of the globe at the fornix - Continuous with the palpebral conjunctiva
Ciliary muscles
- Regulates shape of the lens - Contraction relaxes tension of the suspensory ligaments and the lens fattens (accommodation) - Regulated by the oculomotor nerve (PSNS)
auricular muscles: Considered in groups rather than independently
- Rostral Auricular Group - Caudal Auricular Group
Muscles that close the jaw
- Temporalis - Masseter - Medial pterygoid - Lateral pterygoid
nervous (inner) layer or pars nervosa retina
- divided into nine layers -The divisions of the retina can only be seen histologically!
the posterior pole of the eye
- internally, is referred to as the fundus
Bony promontory
- ventral expansion of the petrous temporal bone
Scutiform cartilage
-Acts like a sesamoid bone... attachment site for muscle tendons to allow for redirection of force for auricular muscles
External (outer) ear
-Auricle (pinna) -Ear canal -Vertical part -Horizontal part: external acoustic meatus
In addition to the auricular cartilage, there are two other cartilages affiliated with the ear
-Auricular cartilage -Annular cartilage: holds ear to skull element -Scutiform cartilage
Inner ear
-Housed in petrous part of temporal bone -Osseous labyrinth -Membranous labyrinth
Middle ear
-Housed in tympanic part of temporal bone -Tympanic membrane (ear drum): separates the external and middle ear -Tympanic bulla (tympanic cavity) -Auditory ossicles with associated muscles and ligaments -Communicates with the nasopharynx via the auditory tube
Terminology for the Regions and Planes of the Eye
-The terms anterior and posterior are used instead of rostral/caudal - The equatorial plane divides the anterior and posterior regions of the eye equally -the sagittal plane divides the eye into right and left halves -Horizontal planes divide the eye into dorsal and ventral parts
both eyelids (palpebrae)
-are lined by haired skin externally and mucous membrane internally -Medial and lateral palpebral ligaments anchor the commissure (Medial ligament is more developed)
Parasagittal planes
-are vertical planes off of the midline
left oculomotor nerve dysfunction
-dilated, unresponsive left pupil but normal menace responses bilaterally. Note the slight ptosis in the left eye (ptosis = drooping of the eyelid) -with complete GVE neuronal deficit and partial GSE neuronal deficit. About 6 months later generalized seizures occurred, and computed tomography imaging was performed
Coronal planes
-divide the anterior/posterior regions of the eye unequally
The auricle (convex and concave surfaces) is covered by?
-hairy skin which extends into the ear canal
Visible portion of the external ear
-has several regions that provide important surgical landmarks • Helix (outer margin of ear) • Scapha • Anthelix (adjacent to helix) • Tragus • Antitragus • Tragohelicineincisure • Intertragicincisure • Cutaneousmarginal pouch (ticks like it here)
The muscles of mastication
-impart movement of the temporomandibular joint -the digastricus m., along with gravity, opens the jaw - 4 muscles close the jaw
An infection in CSF can be seen?
-in the eye
plica semilunaris (third eyelid)
-is a concave fold of palpebral conjunctiva that protrudes from the medial angle of the eye -supported by a T- shaped cartilage -superficial gland of the third eyelid
conjunctiva
-is a continuous mucous membrane that lines the inner palpebrae and part of the globe • Palpebral conjunctiva (10) • Bulbar conjunctiva (11)
optic nerve
-neuron processes of the ganglion cells of the retina converge to form it -begins at the optic disk, where these axonal processes exit the caudal aspect of the globe of the eye -blind spot
Blepharitis
-periocular alopecia and erythema associated with allergic dermatitis. -the thick ocular exudate is caused by keratoconjunctivitis sicca (KCS) and the prolapsed third eyelid (cherry eye).
The optic retina has two layers:
-pigmented (outer) layer or stratum pigmentosum (retinal layer 1) -nervous (inner) layer or pars nervosa retina
Modified hairy skin with glands (modified sweat glands)
-produce cerumen is found within the ear canal. *Ceruminous gland adenomas (can be cancerous in cats) *Otitis externa and dermatologic disease
blind spot
-retinal vessels also enter and leave here -Seen in fundic exam (or back of the eye or posterior part)
Retractor bulbi mm
-retract the eyeball deep into the orbit - Protective mechanism - Surrounds the optic nerve (8)
lacrimal glands
-secretions keep the surface of the eye moist and clean, and provide nourishment to the eye flow of secretion: -secretes serous fluid into the superior conjunctival sac -secretion flows over cornea (blinking) -Lacrimal lake -Passes through puncta and into lacrimal canaliculi (1, 5) -Lacrimal sac -Drains into nasolacrimal duct (3) -Dissipated via convection in nasal cavity
The extensive movement of the auricle is permitted by the?
-the attachment of a complex group of auricular muscles -Controlled movement of the auricle
annular cartilage connects the cartilagenous meatus of the horizontal canal with?
-the bony external acoustic meatus
The shape of the pinna is dependent upon ?
-the composition of the fibroelastic auricular cartilage . • The collagen/elastin composition varies among species and breeds
cat & Pupillary constriction picture
-the constricted right pupil. Pupillary constriction = PSNS -so this results from loss of counteracting SNS innervation (pupillary dilation = SNS).
The orbit protects? and serves as an attachment for?
-the eye and adnexa -serves as an attachment site for extrinsic muscles
retinal detachment
-the separation between the visual or optical part and the non-visual part
The vascular tunic (a.k.a., uvea) is comprised of three regions
1. Choroid (14) 2. Ciliary body (4) 3. Iris (7) -Continuous with the pia- arachnoid layers of the CNS
The fibrous tunic is comprised of two regions?
1. Cornea (transparent anterior 1⁄4) 2.Sclera (opaque posterior 3⁄4) -Continuous with the dural layer of the CNS
The internal tunic, or retina, which can be divided into two regions
1. Visual or optical part, covers the choroid (1) 2. Non-visual part, covers ciliary body and iris -can't be grossly distinguished
three ear types
1. non-erect or lop-eared 2. erect or v-haped 3. semi-erect or lobated
Compartments and Chambers of the Eye
Anterior compartment posterior compartment
Thelazia californiensis
Dog eyeworm
Pathologies/Disorders of the Ear and Eye
Pathologies/Disorders of the Ear and Eye
the external ear is necessary for?
Sound collection and sound localization
Superficial Muscles of the Head & Muscles of Mastication
Superficial Muscles of the Head & Muscles of Mastication
inner vs. outer layer of the optic cup
inner: process light outer: pigmented
The size and shape of the pinna determines which?
sound frequencies are collected optimally and also may reduce noise
The middle ear is located in the air-filled tympanic cavity of the temporal bone
• Auditory tube • Tympanic bulla • Bony promontory • Ossicles (malleus, incus, stapes)
Intrinsic Muscles of the Eye
• Ciliary muscles • Pupillary muscles
vitreous body
• Helps to maintain the shape of the eye • Maintains necessary intraocular pressure to prevent retinal detachment - Established during development -degeneration (liquefaction) of the vitreous body may predispose to retinal detachment
Superficial Structures
• Lips (superior and inferior) • Nose • Philtrum • Whiskers • Cheeks (buccae)
Regions of the Eye (Overview)
• Orbit • Eyeball • Ocular adnexa
Muscles of Facial Expresion
• Platysma • Orbicularis oris • Orbicularis oculi • Buccinator • Levator nasolabialis • Auricular muscles
The external ear is supported by the auricular cartilage
• Proximal end of this cartilage = vertical and horizontal ear canals • Distal end of this cartilage = pinna
bony orbit
• Several bones contribute to the orbital margin • The bony orbit is complete in the horse, ox, and goat • The bony orbit is incomplete in the dog ( completed orbital ligament) and cat
Three divisions of the ear allow for the transformation of sound pressure waves into electrical energy
• The external ear captures sound (longitudinal) waves and transmits this energy to the middle ear via the tympanic membrane • The ossicles of the middle ear convert these pressure waves into mechanical energy • Vibrations at the oval window by the stapes produces pressure waves within the perilymph of the inner ear • Movement of the perilymph displaces the tectorial and basement membranes, stimulating firing of electrical impulses by cochlear neurons.
There are three tunics of the eye
• Tunica externa (fibrous tunic) • Tunica media (vascular tunic, choroid) • Tunica interna (retina)
Ocular Adnexa
• accessory srutcutres - Protection (palpebrae, third eyelid, conjunctiva, retrobulbar fat) - Movement (extrinsic ocular muscles) - Tear production (lacrimal gland/apparatus, gland of third eyelid) - Blood supply and innervation • Trochlea