The inner ear
In the inner ear (auris interna; labyrinth; inner ear) is the cochlea, where sound is converted into nerve impulses. Right next to it is the organ of balance (vestibular organ). In contrast to the middle ear, the inner ear is filled with fluids, the so-called peri- and endolymph.
Both fluids have different chemical compositions. The skull bone, in which the inner ear is located, is called petrous bone and gives an exact shape (bony labyrinth). To the bony labyrinth are also added the cochlea, in which the auditory organ lies, the atrium in the ear (vestibulum), the bony archways, in which the organ of equilibrium lies and the internal auditory canal (internal acoustic meatus) with the auditory and vestibular nerves (vestibulocochlear nerve, static acoustic nerve, 8th cranial nerve).
The cochlea and the organ of hearing (organ of Corti)The organ of hearing in the ear lies within the bony cochlea. The cochlea winds spirally around its own axis. It consists of three channels one above the other, the tympanic staircase (scala tympani), the cochlear duct (ductus cochlearis) and the atrial staircase (scala vestibuli).
Between the three ducts are thin skins (membranes) (Reissner’s membrane and basilar membrane), which can lead to hearing loss or tinnitus if injured (e.g. Meniere’s disease). The actual sensory organs for hearing are located in the cochlear canal in the ear, where mechanical waves are converted into nerve impulses. You can find more anatomical details in our topic: Inner earIn the event of inflammation (pharyngitis, rhinitis), the surrounding tissue in the nasopharynx can swell to such an extent that the ear trumpet in the ear becomes too narrow and can no longer perform its function as a pressure equalizer.
In the case of flu-like infections, a similar feeling of pressure can therefore develop. When swallowing, yawning or artificial air-pressing, as is taught to divers, the difference in pressure can usually be compensated for in healthy people. The organ of balance in the earThe human organ of balance registers two types of acceleration: Linear acceleration and angular acceleration.
We experience linear acceleration in the ear when we start a car, when we are pressed into the seat, or when we would fly up in a rocket. Angular acceleration means any change in the position of our head from the upright position. Two atrial sacs (utriculus and sacculus) in the ear are responsible for registering linear acceleration.
They are equipped with sensory cells that are bent during linear acceleration. When bent, they become excited and send signals to the brain, so that we become aware of the acceleration. The arcade system in the ear is available for the perception of angular acceleration.
Since we must perceive changes in our position in all three dimensions, we have three archways. They are filled with a liquid (endolymph). When the head is moved, this fluid stops due to its inertia and thereby bends a sensor (dome, cupula) in the semicircular canal.
The cupula is deflected against the head movement and registers a change in speed (= acceleration).The faster the head position is changed, the more the dome is deflected. Both sensor systems – sensory cells of the atrial sacs and the domes of the archways – are connected to a nerve (nervus vestibulocochlearis, 8th cranial nerve), which sends all information about changes in position to the brain. If the sensor system is damaged (e.g. in Beningning paroxysmal positioning vertigo (BPLS), benign positioning vertigo) or if the 8th cranial nerve (neuritis vestibularis) becomes inflamed, we feel dizzy. More information is also available at: Dizziness
