EAR Flashcards
What are the three divisions of the ear
The outer, middle and inner ear
What are the two parts of the outer ear
The auricle and the external auditory meatus
What are the parts of the auricle
Helix, antihelix, concha, tragus, antitragus and lobule
What makes up the external auditory meatus
Cartilage 2/3, and bony part 1/3
What is the innervation of the external ear
Superior lateral- lesser occipital
Inferior lateral- greater auricular nerve
Medial- auriculotemporal branch of V3
Also vagus and facial innervation
Middle ear boundaries
Tympanic membrane, concha
Four parts of temporal bone
Squamous, mastoid, petrous and tympanic
What part of the temporal bone holds the middle and inner ear
Petrous part of temporal bone
What are the six walls of the middle ear
The lateral/ tympanic wall, the medial/ labyrinthine wall, the anterior wall, the posterior/mastoid wall, the floor/ jugular wall and the roof/ tegmental wall
Describe the mastoid area
Posterior to the epitympanic recess is the auditus to the mastoid antrum (mastoid part of temporal bone). Has air filled spaces called mastoid cells. The mucous membrane lining the mastoid antrum is continuous with the mucous membrane throughout middle ear.
Describe mastoiditis
Infection within mastoid area- can spread from middle ear infection. If the cranial vault is breached bacteria may enter cranial cavity and menegitis ensues.
What nerve should be avoided when draining pus from mastoiditis
Facial nerve
Describe the tympanic plexus
Gives off tympanic branches that supply mucosa of inner ear and petrosal nerve which give off parasympathetic supply to parotid gland. Branches from CIX
What enters the middle ear through the posterior wall
Pyramidal eminance for tendon of stapedius
corda tympani nerve
What enters/exits the ear through the anterior wall
The tensor tympani muscle
Pharyngotympanic tube (links nasopharynx to middle ear)
Corda tympani nerve exits, branches of carotid plexus enters.
What does the lateral wall consist of
The tympanic membrane and the epitympanic recess
What are features of the medial wall of the middle ear
The tympanic plexus on promontory. Oval and round window, lesser petrosal. Also prominence of facial nerve canal, and prominence of lateral semicircular canal
What is the innervation of the middle ear
The tympanic plexus, C9-10-7, sympathetic.
What is the arterial supply of the middle ear
External carotid and its branches.
What is venous drainage of the middle ear
Pterygoid plexus, superior petrosal sinus
Describe the chorda tympani nerve
A branch of the facial nerve carrying taste sensation… travels through the middle ear.
What are the parts of the tympani membrane
Pars flaccid, The lateral process of the malleus, the handle of malleus, the umbo. The posterior and anterior malleolar folds and the cone of light
What may you see in a middle ear infection of child
Prominent lateral process and umbo due to not being able to equalise pressure with blocked eustachian tube to nasopharynx.
Where does lesser petrosal nerve exit skull
Foramen ovale
What does the semicircular canal have within it
A structure that determines motion?
Where does chorda tympani nerve enter the middle ear
Mastoid/posterior wall
Three bony structures of middle ear
Stapes, malleus, incus
Innervation of the middle ear
9, 10, 7 and sympathetic.
What is the marker on the ear used for the surface anatomy of the parotid duct
Tragus
What give superficial sensation to the external ear
Auriculotemporal, lesser occipital (C2), greater auricular and some vagus and facial
What part of the temporal bone is the middle and inner ear located
Middle cranial fossa, petrous part
What separates middle ear from the middle cranial fossa
Tegman tympani, thin layer of bone that divides the middle ear from the roof.
What sits inferior to the middle ear
Jugular vein
What nerve enters the floor of the middle ear
Tympanic nerve branch of 9
What forms the lateral wall of the middle ear
The tympanic membrane
What nerve runs along the deep surface at the top of the tympanic membrane
Chorda tympani (7), provides taste to anterior 2/3 tongue
Name all the anatomy of the tympanic membrane
Cone of light, umbo, handle of malleus, lateral process of the malleus
What are prominent in middle ear infections
Umbo (tip of malleus), lateral process of malleus
What structures form the medial wall
Promontory, tympanic plexus (tympanic branch of 9, lesser petrosal, branch from internal carotid plexus , round and oval windows,
Which foramina of the skull does the lesser petrosal exit
Foramen ovale
Describe the course of the lesser petrosal
Branch of glossopharyngeal from tympanic plexus. Enters skull via the lesser petrosal hiatus, travels across middle cranial fossa exits skull at foramen ovale, travels through infratemporal fossa and hitchickes to auriculotemporal nerve (v3) to supply PS to parotid gland
Structures on the anterior wall
Eustachian tube, lesser petrosal, branch of external carotid, tensor tympani
Where does mastoiditis occur
In the mastoid air cells, enters via posterior/ mastoid wall.
What wall does chorda tympani enter the middle ear
Posterior wall
What is the blood supply to the middle ear and external aucoustic meatus
Branches of external carotid
