This document discusses diseases of the external ear that can affect hearing. It begins with the anatomy and physiology of the external ear, including the pinna, external auditory canal, and tympanic membrane. It then examines various diseases of the external ear like congenital disorders (anotia, microtia, atresia), infections (furuncle), impacted earwax, foreign bodies, exostoses, and otitis externa. These conditions can lead to conductive hearing loss by obstructing sound transmission through the external ear to the middle ear and eardrum. Early diagnosis and treatment of external ear diseases are important to prevent permanent hearing impairment.

1. DISEASES OF EXTERNAL EAR
AND ITS EFFECT ON
HEARING
Dr Abrar Asif
M.B.B.S
M.PHIL PUBLIC HEALTH
MS SLP
DLO

2. outline
ANATOMY OF EXTERNAL
EAR
PHYSIOLOGY OF HEARING DISEASES OF EXTERNAL
EAR AFFECTING HEARING

3. Anatomy of External ear
◦ The external ear consist of three parts
1. Auricle or pinna
2. External acoustic canal
3. Tympanic membrane

4. Anatomy and physiology of Auricle(pinna)
◦ Made up of framework of yellow elastic cartilage
◦ Projects from lateral side of the head( size, shape and angle varies)
◦ Several elevations and depressions
◦ The only visible part of the ear with its special helical shape.
◦ It is the first part of the outer ear’s anatomy that reacts to sound. The pinna’s function is to act as a kind of funnel which assists
in directing the sound further into the ear. Without this funnel the sound waves would take a more direct route into the
auditory canal. This would be both difficult and wasteful, as much of the sound would be lost, making it harder to hear and
understand the sounds.
◦ The pinna is essential due to the difference in pressure inside and outside the ear. The resistance of the air is higher inside the
ear than outside because the air inside the ear is compressed and thus under greater pressure.

5. ◦ In order for the sound waves to enter the ear in the
best possible way the resistance must not be too
high.
◦ This is where the pinna helps by overcoming the
difference in pressure inside and outside the ear.
◦ The pinna functions as a kind of intermediate link
which makes the transition smoother and less brutal
allowing more sound to pass into the auditory canal
(meatus).

6. Anatomy and physiology of External acoustic
(auditory) canal
◦ Extends from the bottom of the concha to the tympanic membrane
◦ Measures about 24mm along its posterior wall
◦ Divided into two parts
1. Cartilaginous (outer 8mm of the canal)
2. Bony (inner 16mm of the canal)
◦ Outer part is directed upward , backward and medially
◦ Inner part directed downward , forward and medially
◦ Isthmus :
The narrowest part of the ear canal (isthmus) is located near the junction of the cartilaginous and bony canals

7. ◦ Once the sound waves have passed the pinna, they move
two to three centimeters into the auditory canal before
hitting the eardrum, also known as the tympanic
membrane.
◦ The external auditory canal’s function is to transmit sound
from the pinna to the eardrum

8. Anatomy and physiology of tympanic membrane
◦ Partition between external acoustic canal and middle ear
◦ Obliquely set & its posteriosuperior part is more lateral than anterioinferior part.
◦ 9-10mm tall ,8-9mm wide & 0.1mm thick
◦ Divided into two parts
1. Pars tensa (most part of T.M periphery form ring known as annulus tympanicus )
2. Pars flaccida (sharpnell’s membrane)
◦ The eardrum is an extremely sensitive part of the outer ear anatomy. Pressure from sound
waves makes the eardrum vibrate
◦ The vibrations are then transferred to the tiny bones in the middle ear
◦ external auditory canal also functions as a natural hearing aid which automatically amplifies
low and less penetrating sounds of the human voice. In this way the ear compensates for
some of the weaknesses of the human voice, and makes it easier to hear and understand
ordinary conversation

9. Physiology of hearing
◦ In order for a sound to be transmitted to the central nervous system, the energy of the sound undergoes three transformations.
◦ First, the air vibrations are converted to vibrations of the tympanic membrane and ossicles of the middle ear. These in turn
become vibrations in the fluid within the cochlea. Finally, the fluid vibrations set up traveling waves along the basilar membrane
that stimulate the hair cells of the organ of Corti. These cells convert the sound vibrations to nerve impulses in the fibers of the
cochlear nerve, which transmits them to the brainstem, from which they are relayed, after extensive processing, to the primary
auditory area of the cerebral cortex, the ultimate Centre of the brain for hearing. Only when the nerve impulses reach this area
does the listener become aware of the sound.
◦ The human ear is most sensitive to and most easily detects frequencies of 1,000 to 4,000 hertz, but at least for normal young
ears the entire audible range of sounds extends from about 20 to 20,000 hertz

10. Diseases of external ear affecting hearing
◦ Disorders of the outer ear compromise a range of ear problems that exist or are
occurring in the external part of your ear, the pinna, the ear canal, and the eardrum
(tympanic membrane) that can lead to conductive hearing loss.
◦ Congenital disorders
◦ Anotia :
◦ complete absence of pinna and lobule i.e sound waves do not travel well through the ear and
sound is not conducted efficiently from the outer ear canal to the eardrum thus leading to
conductive hearing loss

11. ◦ Microtia :
◦ occurs in approximately one in 10,000–20,000 live births as a result of the aberrant development of the first and second branchial arches. its a congenital
deformity where in the pinna is either small, abnormally shaped, or absent. It can occur in just one side or on both sides.
◦ Leads to conductive and mixed hearing loss
◦ Atresia:
◦ is a malformation of the external ear canal. It is usually on just one side and it can be a complete or partial closure. The extent of the closure directly affects
that person’s conductive hearing loss

12. ◦ Diseases of external auditory canal
◦ Fruncle: A Furuncle is a painful infection of a hair follicle located in the ear canal. It is usually caused by staphylococcus aureus bacteria.
Hearing loss may occur when a furuncle completely occludes the ear canal leading to conductive hearing loss
◦ Impacted wax:
An accumulation of wax in the ear canal which can affect the flow of sound to the tympanic membrane. A little bit of wax is good for
the ear canal as it provides lubrication and protects the ear from bacteria and insects. Excessive cerumen can cause problems with hearing and
balance.
◦ Foreign body occlusion:
Foreign bodies can be inorganic or organic such as beans or beads, cotton tips, and even insects. It can cause trauma to the ear canal,
the tympanic membrane and even the middle ear. Leads to conductive hearing loss
wax
Foreign
body
Foreign
body and
wax

13. ◦ Exostoses:
Exostoses are benign, bony growths covered by skin. These are often seen in those who have been repeatedly exposed to cold water
(i.e. swimmers).
exostosis can completely block the ear canal causing conductive hearing los
◦ Keratosis obturans
is an obscure entity characterized by accumulation of desquamated keratinous material in the bony portion of the external auditory
canal.
Patients with this condition typically present with severe otalgia, conductive hearing loss, and global widening of the external
auditory canal.

14. ◦ Otitis externa :
is a condition that causes inflammation (redness and swelling) of the external ear canal.