Ear Lecture Flashcards
What is the Auricle?
Single piece of elastic cartilage covered with skin with hair, sweat, and sebaceous glands
What is the role of the auricle?
To funnel the sound waves into the external acoustic meatus
Where does the auricle get its blood supply from?
Posterior auricular artery & Superficial temporal artery
What is the nerve supply for the auricle
Great auricular & auriculotemporal
What are the lymph nodes that drain the auricle?
Superficial parotid nodes, retroauricular nodes, deep cervical nodes, superficial cervical nodes
What is the make up of the external acoustic meatus?
Lateral 1/3 is cartilaginous and the medial 2/3 is bony
Where does the EAM get its blood supply?
Posterior auricular artery, Deep auricular of maxillary artery, Superficial auricular artery
Where vein does the EAM drain into?
External jugular vein, Maxillary vein, Pterygoid plexus
What nerves supply the EAM?
Auricular branch of auriculotemporal nerve V3, Facial nerve via tympanic plexus, Auricular branch of vagus
Where is the lypmhatic drainage for the EAM?
Mastoid tip area, Pre-auricular nodes, Upper deep cervical
What is the role of the tympanic Membrane
To seperate the external ear from the middle ear.
explain the make up of the TM?
Externally it is covered by thin fibrous membrane in internally with mucous membrane.
Where does the TM get its blood supply from?
Deep auricular artery of maxillary artery, Stylomastoid arteries of posterior auricular, Tympanic arteries of maxillary
What veins do the TM drain into?
External jugular vein, Transverse sinus, Veins of dura matter, Venous plexus of auditory tube
Where does the TM get its nerve supply from?
Auriculotemporal nerve V3, CN VII, IX, X
What are the contents of the tympanic cavity?
Auditory ossicles, two muscles, chorda tympani nerve, tympanic plexus of nerves
What are the boundaries that make up the Tympanic cavity?
Roof: Tegmental wall Floor: Jugular wall Lateral: Membranous wall Posterior: Mastoid wall Anterior: Carotid wall
What is significant about the jugular wall?
It is the point where the internal carotid artery and internal jugular vein diverge
What are the contents of the lateral wall of the tympanic cavity?
Fenestra vestibuli or oval window- base of staples fixed by annular ligament & fenestra cochlea or round window
What are the contents of the posterior wall of the tympanic cavity?
Aditus to the mastoid antrum- from epitympanic recess
pyramidal eminence and stapedius muscle
aperture for chorda tympani
What are the contents of the anterior wall of the tympanic cavity?
Tensor tympani muscle, auditory tube
Explain the make up of the auditory tube.
Anterior 2/3- cartilaginous; Posterior 1/3- bony
Where is the auditory tube the widest and what is found in relation to this opening?
Widest at pharyngeal end- opens opposite the nasal meatus with tubal tonsil near the opening
Opening into tympanic cavity is below processes cochleaformis
Where does the Auditory tube get its blood supply from?
- Ascending pharyngeal from external carotid
- Middle meningeal from maxillary
- Artery of the pterygoid canal from maxillary
What vein does the auditory tube drain into?
Pterygoid plexus
What nerve supplies the auditory tube?
nerves from the from tympanic plexus and pterygopalatine ganglion
Where would you find the auditory ossicle?
From the TM to the fenestra vestibuli
What is the role of the auditory ossicle?
To amplify the force of the sound wave and decrease the amplitude.
Explain the malleus.
o Head in epitympanic recess- articulates with head of incus
o Handle- embedded in tympanic membrane and attachment of the tensor tympani muscle
o Neck- crossed medially by the chorda tympani muscle
Where would you find the incus?
Body is in the epitympanic recess and articulated with the head of malleus.
The lenticular process at the tip of the long process- articulates with stapes
Where would you find the stapes?
o Head- laterally articulates with lenticular process of incus
o Base- fits into fenestra vestibuli
Where is the origin of the tensor tympani muscle?
Superior surface of cartilaginous auditory tube, greater wing of sphenoid, and petrous part of temporal bone
What innervated the tensor tympani muscle?
Mandibular nerve through fibers passing through otic ganglion
Where does the tensor tympani muscle insert?
Handle of malleus.
What is the action of the tensor tympani muscle?
pulls malleus medially, tensing tympanic membrane and damping vibration-reduces perceived amplitude of sound
Where is the origin of the stapedius muscle?
The pyramidal eminence.
Where doe the stapedius muscle insert?
Neck of stapes
What nerve innervates the stapedius muscle?
Facial Nerve
What is the action of the stapedius muscle?
Dampens vibrations passed to the cochlea via oval window
What are the 4 things that make up the bony labyrinth?
Cochlea, Bony labyrinth, Vestibule, Semicircular canals
What is contained in the bony labrinth?
It contains fluids called perilymph which is similar to ECF
What is found in the vestible?
A camber containing the saccule and utricle
What does the vestibule communicate with?
It communicates with the posterior cranial fossa through aqueduct of vestibule
What is the semicircular canals made up of?
3 canals and 5 openings to the vestibule. The anterior and posterior canal share the same opening which is the lateral canal. Each of the canals are at right angles to each other. It forms 2/3 of a sphere and is dilated at one end which is called the ampulla.
Where is the membranous labyrinth found?
It follows the course of the bony labyrinth and is suspended by CT. It also contains a fluid called endolymph.
What is the role of the semicircular duct?
It communicates with the utricle at the 5 openings.
What is the role of the utricle?
It communicates with the saccule through the utriculosaccular duct and this is where the endolymphatic duct emerges.
What is the role of the saccule?
To communicate with the cochlear duct through the ductus reuniens.
What makes up the cochlear ducts?
It has an organ of corti and is enclosed by basilar and vestibular membranes.
What is the role of the macula in the utricle and saccule?
They are static receptors that help for the position of the head.
What is the role of the crista ampullaris
They are the motion receptors in the semicircular ducts.
What is the modiolus in the cochlea?
Where the cochlea turns around the central body core.
Where would you find the basal spiral?
a Promontory on the medial wall of the tympanic cavity
What is the apex of the cochlea?
The capula
What is the osseous spiral?
A shelf of bones that spirals up the sides of the modiolus.
What is the base of the spiral canal?
The modiolus which is pierced by several calans through its long axis.
What is found in the spiral canal?
Spiral ganglia which sends peripheral branches to the organ of corti on the top of the basil membrane
Where is the basilar membrane found?
attached centrally to the osseous spiral lamina and peripherally to the sides of the cochlea by spiral ligaments.
What are the two regions the cochlear duct are seperated into?
Scala vestibuli – opens into the vestibule and scala tympani at helicotrema.
Scala tympani – opens into tympanic cavity at fenestra cochlea and communicated with the subarachnoid space through cochlear aqueduct.
