Download External ear

Objectives:

By the end of this lecture the student will
be able to:
List the function of the ear
2. Recognize & describe the different
parts of the ear
3. Draw a simple illustrative diagram for
the ear
1.
Ear

The ear is the organ of hearing. It contains
the organ of equilibrium (vestibular
apparatus).
It consists of 3 parts:
1. External ear.
2. Middle ear (tympanic cavity).
3. Internal ear (labyrinth).

External ear:

It includes:
I. Auricle (ear pinna):
It is formed of elastic
cartilage covered on both
side by skin.
It projects from the side of
the head.
Its function is to collect the
sound waves into the
external acoustic meatus.
II. The external acoustic
meatus:
This is the canal between the
auricle and the tympanic
membrane.
The lateral third is
cartilaginous while its medial
two-thirds are bony.
This meatus has S-shaped
curve.
Tympanic membrane:
- It separates the external ear from the middle ear.
- When examined by autoscope or direct light the
anteroinferior part of the membrane appears bright,
forming what is called cone of light.
- The membrane is formed by 3 layers:
1- Outer layer: Formed by skin.
2- Middle layer: Formed of fibrous tissue containing
the bundle of malleus and chorda tympani nerve
(branch from the facial nerve).
3- Inner layer: Formed of mucous membrane. A
branch of vagus nerve supplies the outer surface of
the membrane, while the inner surface is supplied
by the glossopharyngeal nerve.
Middle ear (tympanic cavity):

It is a small cavity in the temporal bone in
the skull. It lies medial (inner aspect) to the
tympanic membrane and lateral to the
inner ear.

It is connected to the nasopharynx by the
auditory tube, so it contains air. It contains
small mobile bones called ear ossicles,
which transmit the sound vibrations from
the tympanic membrane to the inner ear.
Applied anatomy:

In tonsilities and following tonsillectomy, there
is referred pain in the middle ear due to the
fact that the glossopharyngeal nerve supplies
both the oropharynx and the middle ear.
Internal ear (labyrinth):

1.
2.
It is formed of:
Bony labyrinth.
Membranous labyrinth.
Possible questions:
Mentiom the composition of the ear.
 Describe the tympanic membrane.

‫‪Assignment:‬‬
‫‪Students will asked to draw a simple‬‬
‫‪illustrative diagram for the ear‬‬
‫‪ ‬حميد عبد االله حميد مجيد‬
‫‪ ‬دعاء السعيد رشاد قطب علي‬
‫‪ ‬دينا داود وليم داود يعقوب‬
‫‪ ‬دينا عبد الرافع عبد الرازق الجعيدي‬
‫‪ ‬رامى رافت لطفى عيسى‬
‫‪ ‬رانيا محمد احمد محمد الشرقاوي‬
‫‪------------------- Opened discussion session.‬‬
‫‪‬‬