Ear Flashcards
Why is a rash seen on the concha of the ear when the ganglion of facial nerve is affected by Herpes Zoster infection?
Some fibers of the facial nerve travel with the auricular branch of the vagus nerve as it goes to supply sensation to concha
Enumerate cutaneous innervation of auricle.
Lateral surface
(upper 2/3rd –> Auriculotemporal nerve)
(concha –> Auricular branch of vagus nerve )
(lower 1/3rd/ear lobule –> Great auricular nerve
Nerve roots of great auricular nerve
C2 - C3 ventral rami
type of cartilage of the external acoustic meatus
elastic cartilage
Boundaries of external auditory meatus
tympanic plate forms anterior, inferior, and posteroinferior boundaries
Squamous part of temporal bone forms its posterosuperior boundary
Glands that secrete ear wax
Ceruminous glands
Location of constrictions of External auditory meatus
One is found at junction between its bony and cartilaginous parts
The other gives EAM its narrowest point and is found 6 mm lateral to tympanic membrane
External auditory meatus sensory innervation
Anterior wall and superior wall innervated by auriculotemporal nerve
Posterior wall and floor innervated by auricular branch of vagus
Effects of syringing external auditory meatus to remove ear wax
Stimulates auricular branch of vagus nerve = cough reflex, vomiting, and cardiac arrest
Clinical relevance of cymba conchae’s relation to suprameatal triangle
It lies at the level of suprameatal triangle so used as a landmark to make a hole to drain pus in mastoid antrum.
In adults, the hole is made to be 12 mm long, while in infants it’s made to be 2 mm long.
Boundaries of suprameatal triangle
Superior: posterior root of zygomatic arch
Anterior: posterior border of external acoustic meatus
Posterior: line joining the two
Angle tympanic membrane lies in relation to floor of EAM
55 degrees
Anatomical parts of tympanic membrane as seen on medial surface
Upper Pars Flaccida (lacks fibrous tissue, bounded by anteiror and posterior malleolar folds which are folds of the superior aspect of tympanic membrane)
Lower Pars Tensa (has fibrous tissue, the umbo, and its margins thicken to form annulus tympanicus)
True or false: The tympanic cavity resembles a biconvex disc
False: It resembles a biconcave disc
Contents of tympanic cavity
- Air
- Posterior auricular artery (from external carotid) and Anterior tympanic artery (from maxillary artery )
- chorda tympani nerve and tympanic plexus
- Tensor tympani and Stapedius
Lymphatic drainage of tympanic cavity
Parotid nodes
Upper deep cervical nodes
Tympanic plexus formed by
- inferior caroticotympanic nerve
- superior caroticotympanic nerve
( both from sympathetic plexus around internal carotid artery) - Glossopharyngeal nerve tympanic branch
Arterial supply of middle ear cavity
- From external carotid
- Occipital
- Ascending pharyngeal - From internal carotid –> Caroticotympanic artery
- From Maxillary artery
- Middle meningeal artery
- Anterior tympanic
- Deep auricular
Complications of Suppurative Otitis Media
This is infection of middle ear that usually occurs through auditory tube
1. Labyrinthitis: medial wall is eroded affected semicircular canals; leads to vertigo and vomiting
- Meningitis: infection spreads to roof (tegmen tympani) and brain in danger of being affected
- Mastoiditis: infection spreads to mastoid air cells via aditus to mastoid antrum
- Sigmoid sinus thrombosis; when infection spreads to floor (jugular wall) of tympanic cavity, can cause thrombosis of internal jugular vein
- Facial palsy: when infection erodes wall of facial canal on posterior and medial wall
Internal ear is found in which bone?
Petrous part temporal bone
Describe features on lateral wall of vestibule
Has the oval window covered by annular ligament and foot of stapes
Enumerate features on medial wall of vestibule
Posterosuperiorly:
- Utricle
- Fenestrations for upper division of vestibular nerve
Anteroinferiorly
- Saccule
- Fenestrations for lower division of vestibular nerve
The modiolus via its spiral laminae divides the cochlear canal into
Upper Scala vestibuli
Lower Scala tympani
Membranes extending from the spiral lamina of modiulus
Vestibular membrane superiorly
Basilar membrane inferiorly
