LESSON 18

Tympanic Membrane: Structure and Landmarks

Name: Tympanic Membrane: Structure and Landmarks
Uploaded: 2026-11-04T00:29:22+03:00
Duration: 10 min 23 s
Description: We describe the position of the tympanic membrane, or eardrum, its pars tensa and pars flaccida, and its three-layer structure. We learn the otoscopic landmarks, such as the umbo, the manubrium of the malleus and the cone of light, and why they matter clinically.

Year 1
Fall semester
Anatomy I
Ear anatomy
Duration: 10:23

We describe the position of the tympanic membrane, or eardrum, its pars tensa and pars flaccida, and its three-layer structure. We learn the otoscopic landmarks, such as the umbo, the manubrium of the malleus and the cone of light, and why they matter clinically.

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Hello, and welcome to the AIHEAR Audiology Academy.
In this lesson, we meet the thin boundary between the outer and middle ear: the tympanic membrane, or eardrum.
We will learn its parts, its three-layer structure and the landmarks we see through the otoscope.
At the inner end of the ear canal, a thin membrane separates the outer ear from the middle ear.
This structure is the tympanic membrane.
Its outer surface faces the ear canal, and its inner surface faces the air-filled middle ear cavity.
The membrane does not stand upright; it sits at an angle of about fifty five degrees to the floor of the ear canal.
In newborns, the membrane lies more horizontally, which makes otoscopic examination harder in babies.
The first ossicle, the malleus, is firmly attached to the inner surface of the membrane.
Thanks to this connection, the vibration of the membrane is passed directly to the ossicular chain.
The tympanic membrane is a slightly oval membrane about eight to ten millimeters in diameter.
It is only about zero point one millimeters thick.
It is not flat but a shallow cone drawn in at the center, with the tip of the cone pointing toward the middle ear.
This cone shape helps the membrane transmit vibration more efficiently.
Through the otoscope, a healthy membrane looks pearly gray and translucent.
Because it is translucent, middle ear structures behind the membrane can sometimes be seen.
The tympanic membrane has two parts; most of it is the pars tensa, the tense part.
The pars tensa makes up most of the membrane and is the main vibrating surface that transmits sound.
The small part at the top is the pars flaccida, the slack part.
The pars flaccida is also known as Shrapnell's membrane, after the anatomist who described it.
The border between the two parts is formed by the malleolar folds, which run forward and back from the lateral process of the malleus.
The pars flaccida is slacker because the fibers in its middle layer do not form an organized structure.
The edge of the pars tensa thickens into a fibrocartilaginous ring called the annulus.
The annulus sits in the tympanic sulcus of the temporal bone and holds the membrane in place.
At the top, this groove and ring are interrupted; this gap is called the notch of Rivinus.
The pars flaccida attaches directly to bone right at this notch, without a ring.
This structural difference is one reason the two parts behave differently in disease.
Although it is very thin, the tympanic membrane is made of three layers.
The outer layer is stratified squamous epithelium, continuous with the skin of the ear canal.
The middle layer is the fibrous layer, also called the lamina propria, with radial and circular collagen fibers.
These fibers give the membrane both tension and strength; in the pars flaccida, however, they are not organized.
The inner layer is continuous with the mucosa that lines the middle ear cavity.
Embryologically, the three layers come from three different germ layers: ectoderm, mesoderm and endoderm.
The outer layer has an interesting feature: its epithelial cells migrate from the umbo toward the edges.
This migration continues along the ear canal and carries debris outward, so the ear canal cleans itself.
This migration also plays an important part in the natural outward movement of earwax.
Thanks to the same ability to renew, small traumatic perforations can often close on their own.
But the middle layer may not fully regenerate in the healed area, which stays thinner and is described as an atrophic area.
When we look through the otoscope, we see some fixed landmarks on the membrane.
The most obvious is the handle of the malleus, running up and forward from the center; it is called the manubrium of the malleus.
The lower tip of the manubrium is the umbo, the most drawn-in point of the membrane.
At the upper end of the manubrium, there is a small white bump; this is the lateral process of the malleus.
The area just above the lateral process is the pars flaccida.
A bright reflection also spreads down and forward from the umbo; this is the cone of light, or light reflex.
To describe the membrane, we divide it into four quadrants.
A line along the manubrium and a second line through the umbo at right angles to it divide the membrane into four quadrants.
The cone of light normally lies in the anteroinferior quadrant.
If the membrane is thin, the long process of the incus and the stapes region may be seen in the posterosuperior quadrant.
Using quadrant names when recording findings communicates the location clearly.
For example, a perforation can be described as a small central perforation in the posteroinferior quadrant.
When we assess the membrane on otoscopy, we first look at its color and translucency.
Then we look at its position: is the membrane retracted, or is it bulging outward?
Next we check its integrity: is there a perforation or scar tissue?
The appearance of the manubrium and the lateral process also gives clues.
In a retracted membrane these structures look more prominent, and in a bulging membrane they look faint.
Finally, we look for a fluid level or air bubbles behind the membrane.
A practical tip for otoscopy: the cone of light is seen at five o'clock in the right ear and seven o'clock in the left ear.
This helps you find the anteroinferior quadrant quickly and confirm which ear you are looking at.
However, an absent cone of light does not by itself indicate disease; the shape of the ear canal can also affect it.
Always assess this finding together with the color, position and mobility of the membrane.
The main job of the tympanic membrane is to turn sound waves in the air into mechanical vibration.
When the membrane vibrates, the malleus attached to it moves too, and the vibration passes into the ossicular chain.
The vibrating area of the membrane is much larger than the stapes footplate; this area ratio raises the pressure reaching the inner ear.
The effective vibrating area of the membrane is about fifty five square millimeters, and the footplate about three.
This ratio is the largest part of the impedance matching mechanism of the middle ear.
The membrane also separates the middle ear from the outside and forms a barrier against infection.
An intact membrane also reduces sound reaching the round window directly, so the two windows are not stimulated at once.
The different structure of the two parts also leads to different clinical pictures.
Perforations in the pars tensa are mostly of the central type.
In a central perforation, membrane tissue remains around the hole and the annulus is preserved.
Because the pars flaccida is slacker, it can collapse inward with negative middle ear pressure and form a retraction pocket.
Skin debris collecting in these pockets can turn into a cholesteatoma, a mass that can erode bone.
That is why the pars flaccida region is examined with special care during otoscopy.
We can measure the mobility of the membrane and the middle ear with tympanometry.
In this test, air pressure in the ear canal is varied while we track how easily the middle ear system accepts sound.
With a normal membrane and middle ear, we see a type A curve with its peak near zero.
If the membrane is perforated or the middle ear is full of fluid, the curve flattens; this is called type B.
With a perforation, the telltale clue is a larger than usual volume, because the device also measures the middle ear space.
We will cover tympanometry in detail in later lessons.
The large tense part of the tympanic membrane is the pars tensa, and the small slack part at the top is the pars flaccida.
The membrane has three layers: epidermal on the outside, fibrous in the middle and mucosal on the inside.
On otoscopy, the umbo, the manubrium of the malleus, the lateral process and the cone of light are the key landmarks.
The cone of light is in the anteroinferior quadrant, at five o'clock in the right ear and seven o'clock in the left ear.
Test yourself: In which quadrant of the tympanic membrane is the cone of light normally seen?
The correct answer is B, the anteroinferior quadrant. The cone of light spreads down and forward from the umbo.
In the next lesson, we will explore the middle ear cavity behind the membrane, its walls and its neighbors.
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Prerequisites

LESSON 17 Outer ear anatomy