Ear Anatomy Flashcards
What are the three parts of the ear
external, middle, inner ear
What are the 2 parts of the External Ear?
Pinna/Auricle and External Acoustic Meatus/ear canal
What are the 3 cartilages of the external ear?
Auricular cartilage, Annular cartilage, Scutiform cartilage
Describe the auricular cartilage
Large cartilage of the pinna and external acoustic meatus
Flat distal part- Pinna
Tubular proximal part- External acoustic meatus
Describe the annular cartilage
Small tubular cartilage
Joins auricular cartilage to osseous external acoustic meatus
Describe the scutiform cartilage
Boot shaped cartilage
Located on dorsum of head rostromedial to ear - imbedded in auricular muscles, fascilitates movement
Serves as attachment site of muscles of the ear
Describe the pinna
also called the auricle
Flat distal portion of auricular cartilage covered with haired skin
Highly mobile
Convex caudal surface (medial, caudal)
Concave rostral surface (anterior, lateral)
Funnels sound waves to ear canal
What is the scapha
The large flat inner concave surface of the pinna
Distal to the anthelix
What is the concha
Funnel shaped region of pinna
Proximal to the anthelix
Surrounds the ‘conchal cavity’
What is the helix
Free margin of the pinna
Lateral border of helix and medial border of helix
join at apex of the pinna
Lateral border contains ‘marginal cutaneous sac’
Medial border continued rostrally as crura
What is the tragus
Projection of cartilage along rostral border of concha
Large, quadrangular
Lateral to crura of medial border of helix
What are the incisures
Intertragic incisure -between antitragus and tragus
Pretragic incisure -between medial helix and tragus
What are the four groups of muscles of the pinna
Rostral Dorsal Caudal Ventral
Describe the muscles of the pinna and innervation
Intrinsic and Extrinsic mm
Innervated by CN VII, the facial n
Arranged in layers overtop a fat pad
Scutiform cartilage serves as an attachment for many mm
Describe blood supply to the pinna
External carotid to
Caudal Auricular -> Medial, intermediate, lateral auricular
or to rostral auricular
Branches or auricular aa pass through openings in the auricular cartilage to pass from caudal to rostral
Clin sig of Ear vasculature
The pinna is highly vascularized and can bleed profusely!
in pigs and ox can use ear veins for venipuncture
intermediate auricular v in ox
lateral auricular vein in pig
Describe aural hematomas
Hematoma between auricular cartilage and skin due to ruptured auricular blood vessels
Caused by trauma to the ear
*Self trauma secondary to ear infections
Treatment is drainage and eliminating dead space Untreated ears fibrose and cause disfigurement
What nerves innervate the concave surface of pinna
Facial n - Internal auricular brr of auriculopalpebral n
Vagus n - Auricular br
What nerves innervate the convex surface of the pinna
Mandibular br of Trigeminal n
C2 spinal n - Great auricular n, Great occipital n
Name the two parts of the external acoustic meatus based on tissue type
Cartilaginous part-
Tubular auricular, cartilage Annular cartilage
Osseous part-
Wall of ‘external acoustic meatus’ in tympanic part of temporal bone
Name the two parts of the external acoustic meatus based on orientation.
Vertical part- Tubular auricular cartilage
Horizontal part-Tubular auricular cartilage, Annular cartilage, Bony external acoustic meatus
What lines the ear canal
Lined internally with skin containing glands- Sebaceous glands, Ceruminous glands
How to view Ear canal
Place otoscope in intertragic incisure
Pull pinna laterally and ventrally to straighten canal from L shape
Sensory innervation to skin of ear canal
Facial n - cartilaginous portion
Vagus n - cartilaginous portion
Mandibular n - osseous portion, tympanic membrane
Describe a lateral ear canal resection
Exposes ear canal for improved ventilation (don’t for cases of otitis external, aids in self-cleaning of ear wax that occurs with chewing/movement)
Lateral wall incised at - pretragic incisure and intertragic incisure
External skin edge sutured to skin edge of ear canal
Wha structures need to be considered with lateral ear canal resection
Structures adjacent to the vertical ear canal:
Parotid salivary gland
Brr of the facial n deep to parotid gland: Dorsal buccal br, Ventral buccal br of CN VII, Auriculopalpebral n
Auriculotemporal n
Brr of caudal auricular a
Tributaries to caudal auricular v
List components of the middle ear
Tympanic membrane
Ear ossicles
Tympanic cavity
Auditory tube
(Vestibular window, Cochlear window)
Describe the tympanic membrane
Located at medial extent of osseous ear canal
Separates external ear from middle ear
Concave from external view
Oval in shape
Thin semitransparent membrane- fibrous connective tissue lined with epithelium
What’s visible otoscopically of the tympanic membrane?
Two regions of membrane: pars flaccida dorsally pars tensa ventrally
Attachment of malleus on inner surface of membrane “stria mallearis”
The malleus curves ventrally and points rostrally
Describe the ear ossicles
3 small bones of the middle ear -malleus, incus, stapes
Transmit vibrations from the tympanic membrane to the inner ear
tympanic cavity:
Space bound by the ____ laterally and the _____ medially
Ear ossicles extend across the dorsal tympanic cavity from_____ to ______
______ for the auditory tube located ______
Branches of the ______ and ________, and _________ neurons pass within the tympanic cavity
tympanic bulla
petrous temporal bone
tympanic membrane
vestibular window
Ostium
rostroventrally
facial
glossopharyngeal nerves
post ganglionic sympathetic
Tympanic cavity species differences
Tympanic cavity is partially divided by the septum bullae
More prominent and notable in the cat
clinical importance of nerves traveling in tympanic cavity
Can be affected by otitis media interna
Ear infection can cause horner’s syndrome
Auditory tube:
Tube connecting ____ to ______
Allows for _______ between the ______ and the atmosphere
The ________ houses the auditory tube
-extends from ____ aspect of the _____ to open on the _____ skull
tympanic cavity
nasopharynx
equalization of pressure
tympanic bulla
musculotubular canal
rostral
tympanic bulla
ventral
Describe the internal ear purpose and location
Organ for hearing and balance
Located within the petrous part of the temporal bone
What are the two labyrinths of the internal ear and what do they contain
Osseous labyrinth:
Cochlea, Vestibule, Semicircular canals
Membranous labyrinth:
Cochlear duct, Sacculus, Utriculus, Semicircular ducts
What are the fluid components of the internal ear
Endolymph (fills membranous part)
Perilymph (fills osseous part)
Nerves to internal ear
CN 8, CN 7
Where does the vestibulocochlear nerve divide into the cochlear and vestibular part
At the osseous labyrinth
What does the cochlear nerve innervate and purpose
innervates the cochlear ducts for hearing
What does the vestibular nerve innervate and purpose
innervates the sacculus, utriculus, and semicircular ducts for balance
Where does CN 8 vestibulocochlear n travel
Travels from brainstem through internal acoustic meatus into petrous part of the temporal bone
