EarSupervised by: Dr Amal Abo El-Monsef

Objectives:

By the end of this lecture the student will be able to:

1. List the function of the ear

2. Recognize & describe the different parts of the ear

3. Draw a simple illustrative diagram for the ear

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):

It is formed of:

1. Bony labyrinth.

2. 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 مجيد حميد االله عبد حميد

علي قطب رشاد السعيد دعاء يعقوب داود وليم داود دينا

الجعيدي الرازق عبد الرافع عبد دينا عيسى لطفى رافت رامى

الشرقاوي محمد احمد محمد رانيا------------------- Opened discussion session.