Download Anatomy of the Ear

By
Dr. Baseem N. Abdulhadi
ENT Specialist
CABMS (ENT), FIBMS (ENT)
Sensory supply of the auricle
Arterial supply of the auricle:
1) Anterior auricular branches
from the superficial temporal
artery.
2) Posterior auricular artery from
the external carotid artery .
3) Branch from the occipital
artery.
The External auditor y canal
The external auditory canal:
• It does not follow a straight course.
• It passes upward in an anterior
direction, then turns slightly
posteriorly still passing upward, and
finally turns again in an anterior
direction with a slight descent.
• On otoscopic examination: gentle
traction of the auricle superiorly,
posteriorly and slightly laterally is
needed to straighten the external
auditory canal.
Clinical correlates:
Otitis externa is an inflammation of the external ear,
usually from moisture in the canal leading to bacterial
or fungal infection (swimmer’s ear) or to an infected
hair follicle (boil). The condition can be painful
because of tightness of the skin lining the canal that is
abundantly innervated.
Increased pain from traction on the auricle or opening
the jaw helps distinguish otitis externa from otitis
media.
Right tympanic membrane
The middle ear (tympanic cavity):
It is an air-filled, mucous membrane-lined cavity in
the temporal bone between the tympanic membrane
laterally and the lateral wall of the inner ear medially.
It consists of two parts:
1. The tympanic cavity proper: immediately adjacent
to the tympanic membrane.
2. The epitympanic recess: superiorly.
Boundaries (Walls) of the middle ear:
The middle ear has 6 walls:
1. Roof (tegmental wall).
2. Floor (jugular wall).
3. Lateral wall (membranous wall).
4. Medial wall (labrynthine wall).
5. Posterior wall (mastoid wall).
6. Anterior wall (carotid wall).
Contents of the middle ear:
1) Auditory ossicles (malleus, incus, and stapes).
2) Stapedius and tensor tympani muscles.
3) Chorda tympani nerve, a branch of CN VII.
4) Tympanic plexus nerves.
Movements of the auditory ossicles
Paralysis of the stapedius muscle:
In patients with facial nerve paralsy, paralysis of
the stapedius muscle is associated with excessive
acuteness of hearing called hyperacusis; this
condition results from uninhibited movements of
the stapes
Clinical correlates:
Ear pain (otalgia) may be referred from the nasal cavity and
paranasal sinuses via the trigeminal nerve, from the
pharynx and larynx via the glosspharyngeal and vagus
nerves, and from the cervical spine via spinal nerves.
Otalgia may be associated with nausea and vomiting, a
response mediated through the vagus nerve and its
innervation of the upper gastrointestinal tract.
The inner ear:
1) The bony labyrinth.
a. Bony cochlea.
b. Vestibule.
Filled with perilymph
c. Three semicircular canals.
2) The membranous labyrinth.
a. Cochlear duct.
b. Utricle and saccule.
c. Three semicircular ducts.
Filled with endolymph
The cochlea: cross section
Clinical correlates:
Otosclerosis is a condition of abnormal bone formation
around the stapes and the oval window, limiting the
movement of the stapes and thus resulting in progressive
conduction deafness.
Conductive deafness is hearing impairment caused by a defect
of a sound-conducting apparatus such as the auditory meatus,
eardrum, or ossicles.
Neural or sensorineural deafness is hearing impairment
because of a lesion of the auditory nerve or the central afferent
neural pathway.
Meniere Syndrome
(endolymphatic hydrops):
It is related to excess
endolymph production or
blockage of the
endolymphatic duct.
Characterized by:
1. Tinnitus.
2. Hearing loss.
3. Vertigo.
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