The 9 parts and bones of the human ear (and their characteristics)

Hearing is made up of the psychophysiological processes that provide living beings with the ability to hear. Human beings are not the only ones who present this sense and, in fact, it should be noted that our hearing capacity is very limited. While our species can hear an auditory frequency of 20 kHz (20,000 hertz), a moth can perceive sound waves of 300 kHz, many magnitudes ahead.

Said quickly and simply, the pinna concentrates the waves that come from the middle, they travel by all auditory structures and cause the transformation of waves into information that travels to the brain. This key step is carried out by the hair cells, located in the organ of Corti. These bodies are permanent and if they are damaged they cannot be repaired, which is why special emphasis is placed on not subjecting our ears to excessively high sound levels.

The sense of hearing is truly interesting, not just in humans. Many mammals, for example, can orient the auditory pin thanks to their cranial muscles and receive information more quickly and accurately. In evolutionary terms, hearing a sound a second before can mean the difference between life and death. Based on these premises and many others,

Next we will tell you all about the 9 parts and bones of the human ear.

• We recommend you read: "The 17 parts of the heart (and their functions)"

What is the morphology of the ear?

The human ear is divided into three distinct sections: external, middle and internal. In addition to its physiological importance, this classification is essential in the clinical setting, since an external ear infection has nothing to do with a bone break in the inner ear. Next, we present the 9 parts and bones of the human ear according to their location. Do not miss it.

1. Outer ear

It is the outermost part of the ear, as its name suggests. In it are the auditory pinna and the external auditory canal.

1.1 Pinna

It is the only visible part of the ear and acts as a “bell” for capturing sound waves.. Interestingly, some scientists argue that certain sections of these structures can be considered vestigial. Despite the fact that we have muscles that could direct the pinna (as is the case with foxes, for example) towards the sound source, it is atrophied and does not seem to have any clear use.

1.2 External auditory canal

A conduit about 2.5 centimeters long and 0.7 square millimeters wide, which extends from the pinna to the eardrum. The external wall of this canal is directly associated with the temporomandibular joint. For this reason, during otitis tasks as seemingly simple as chewing or yawning are difficult.

2. Middle ear

An air-filled cavity of almost square shape, located in the petrous portion of the temporal bone. At the anatomical level, the middle ear is located in the upper part of the cerebellum, between the encephalic masses and the eardrum. We tell you each of its parts.

2.1 Eardrum

The eardrum is a semitransparent membrane, elastic and in the shape of a cone that communicates the auditory canal of the middle ear with the external ear, sealing the first cavity. Vibration of the tympanic membrane is the first step in the conversion of sound waves into nerve signals that the brain can interpret.

2.2 Tympanic cage

A cavity located behind the eardrum that communicates with the nostrils. It is divided into several walls: ceiling, floor, posterior section and anterior section, which includes the entrance to the Eustachian tube. It is lined by mucosa and a simple flat-type epithelial lamina in its posterior part, while the anterior is lined by a ciliated stratified columnar epithelium.

2.3 Ear bones

Perhaps the most important parts of the entire auditory section. These short and irregular bones form a chain located in the tympanic cavity of the middle ear, whose function is transmit the vibrations emitted by the tympanic membrane towards the inner ear, through the oval window (membrane that covers the entrance of the cochlea). We can cite the following generalities of these three bone structures:

• Hammer: It consists of a head, a neck, a manubrium and two processes. Through the incudomalleolar joint, it transmits vibrations from the eardrum to the incus.
• Anvil: With one body and two branches, this irregular bone connects to the hammer through the incudomalleolar joint and to the stapes through the incudostapedial joint.
• Stapes: it has a head, neck, two crosses (one front and one back) and a base. It connects with the anvil and the oval window, and its dysfunction causes otosclerosis.

In summary, these complex structures are responsible for transmitting tympanic vibrations to the Eustachian tube, the next step in the middle ear.

2.4 Eustachian tube

The Eustachian tube is the connecting highway between the middle ear, the back of the nose, and the nasopharynx (throat). Its main functionality is in maintain and equalize the air pressure inside the middle ear with that outside the middle ear. When the tube does not open during swallowing or yawning, pressure differences are generated and various pathologies appear at the otic and auditory level

3. Inner ear

The inner ear is the final part of the auditory system. It is divided into an anterior and a posterior labyrinth. We tell you its parts.

3.1 Cochlea

Formerly called a snail, the cochlea refers to a structure in the shape of a spirally wound tube located in the anterior portion of the inner ear. In turn, it is divided into three different sections: scala tympani, scala vestibuli, and cochlear duct. In any case, the most important thing about this structure is that within it is the organ of Corti, in charge of hearing itself.

Within this organ there are about 3,500 outer and 12,000 outer hair cells. These cells contain apical stereocilia that move with sound vibrations, generating an electrical potential in the cellular environment. This transduction mechanism allows the transformation of the sound wave into electrical impulses that can be analyzed by the brain.

3.2 Lobby

It is the region of the inner ear that is responsible for the perception of body movement, so it is historically (and medically) associated with maintaining balance in mammals. The vestibule contains hair cells, but in this case its function is to detect linear accelerations or decelerations that occur in any of the three planes of space. The otoliths (crystals) in this section, depending on their physiological position, can inform the hair cells of the position of the head and the movements that the living being is making in the space.

3.3 Semicircular canals

A complex structure formed by three very small tubes, whose purpose is also help maintain balance. They are oriented in the three axes of space and are responsible for detecting any angular acceleration movement in any of the physical planes.

When the vestibule or semicircular canals fail, the patient experiences a series of very marked balance problems. These manifest as dizziness, vertigo, unsteadiness, falls, vision changes, and disorientation. For all these reasons, inner ear failures are very obvious from a clinical point of view.

Resume

This time we have introduced you to the 9 parts of the ear, starting with the pinna and sound reception and ending with human balance. If we want you to keep a general idea, this is the following: the waves are received by the ear, the eardrum resonates and transmits the vibrations relevant throughout the bony chains and ultimately the hair cells of the organ of Corti transform this movement into nerve signals electrical.

In addition to hearing itself, auditory structures are also essential in other processes, such as maintaining balance and certain mechanical movements. located on the head (such as chewing). Without a doubt, this biological system is a true work of art from an evolutionary point of view.