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The ear, the hearing organ that is present only in vertebrates, is responsible for the sense of balance and for receiving sound waves, first converted into mechanical vibrations and then into nerve impulses. The most complex structure of the ear, consisting of three parts: the inner ear, the middle ear, and the outer ear, occurs only in mammals.
Structure and functions of the outer ear
The outer ear is made of the pinna and the external auditory canal, separated from the middle ear by the eardrum. The auricle itself is made of cartilage surrounded by cartilage, subcutaneous tissue and skin. It grows up to the age of eighteen, and its shape is inherited.
The different parts of the auricle are:
- heel,
- shuttle,
- dyke,
- concha shell,
- triangular bottom,
- scrap,
- counter-section,
- the lobe of the auricle, which is the only part that is devoid of cartilage.
The turbinate is responsible for collecting sounds from the environment that are passed on to the external auditory canal.
The external ear canal consists of a skin-covered medial bone part and a lateral cartilage part. It is about 3-4 centimeters long, it is bent in the shape of the letter S. At the beginning of the ear canal there are short hairs, the discharge from their sebaceous glands creates earwax, which in too much can lead to clogging of the canal (earwax prevents debris into the ear canal). The ear canal allows the flow of acoustic stimuli to the tympanic membrane – an oval, tense surface with dimensions of approx. 10 x 8,5 mm and a thickness of approx. 100 microns, covered on the outside with epithelium and on the inside with a mucosa.
If the tube becomes clogged, you should not remove the earwax with cotton buds, as this will only push the earwax deeper. In addition, this way we can also damage the eardrum that closes the external auditory canal. In the event of clogging of the conduit, i.e. the formation of the so-called plug, go to the laryngologist for the ear rinsing procedure, or use preparations for this available in pharmacies.
See also: Clogged ear – causes, foreign body in the ear. How to unclog your ear?
Structure and functions of the middle ear
The middle ear is responsible for amplifying the sound waves and bringing them to the inner ear through the oval window. The beginning of the middle ear is a small, air-filled eardrum located just behind the eardrum.
There are three auditory bones in the cavity: a hammer, an anvil and a stirrupwhose task is to strengthen and transmit vibrations of the eardrum to the inner ear (this is possible due to the fact that the surface of the hammer connecting with the membrane is larger than the surface of the stapes, creating a strengthening gear; the eardrum tensioner also plays a huge role, which, when loosening, reduces vibrations too strong sounds and the stapes muscles have an analogous role and they protect us against too loud sound).
The hammer on one side connects to the eardrum and on the other side connects to the anvil, the anvil in turn connects to the stapes. The stapes are connected by a membrane-covered oval window that leads to the vestibule of the inner ear and facilitates the transmission of vibrations to the inside of the cochlea.
Another important element of the middle ear is the Eustachian tube, also known as the Eustachian tube. It is a 35 mm long longitudinal canal that acts as a pressure equalizer on both sides of the eardrum. The trumpet connects the middle ear with the throat, therefore, when the throat and nose are inflamed, the middle ear can also become inflamed and the pharyngeal part of the proboscis closes, which means that during the disease we can hear worse (the pressure in the tympanic cavity is not equalized).
A similar problem occurs when landing an airplane, when the air pressure in the cabin increases. In this situation, yawning or swallowing saliva may help, resulting in a contraction of the flexor muscle of the soft palate, which in turn opens the pharyngeal opening of the Eustachian tube. Through the outlet, air enters the tympanic cavity, which equalizes the pressure with that in the aircraft cabin. Interestingly, candies are distributed on airplanes to protect passengers from such situations because they increase the saliva secretion, which must be swallowed frequently.
Find out more: Clogged ear and tinnitus – what is the cause?
Structure and functions of the inner ear
The inner ear, apart from receiving mechanical vibrations and transforming them into nerve impulses, is also an important element of the sense of balance. Just behind the auditory bones of the middle ear is a fluid-filled vestibule leading to the oval window. Three semicircular canals depart from the atrium, constituting the membranous labyrinth, which inform the organism about the position of the body in space.
Movement of the head causes the fluid and jelly substance to be displaced, which stimulates the sensory cells and transmits nerve impulses for balance to the brain. The right organ of hearing connects to the base of the semicircular canals – the cochlea (the name comes from its appearance, because it resembles a snail shell), a coiled bone canal with a length of approx. 35 millimeters filled with a fluid in which crystals of phosphate or calcium carbonate (otolites) are suspended .
In the center, there are two membranes (the basal membrane and the Reisner membrane, also known as the vestibular membrane) dividing the cochlea into three chambers: the atrium staircase, the cochlea, and the eardrum. The middle staircase of the cochlea contains the Corti organ, which is responsible for the formation of the appropriate nerve impulses. Damage to Corti’s organ would cause complete deafness.
The function of the cochlea is to perceive the vibrations of the liquid and to stimulate nerve impulses, which are transmitted to the hearing center via the auditory nerve. The impulses via the auditory nerve are transmitted to the temporal lobes, where it is analyzed, remembered and assigned specific meanings to individual impulses through the cerebral cortex.
Also check:
- Otitis in a child – causes, symptoms and treatment
- Otitis externa – treatment, symptoms and causes
- Auricle injuries
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