Every child knows that our ears are responsible for hearing; however, balance and spatial awareness are also other important tasks of the inner ear. We explain how the middle ear and inner ear are structured, what their functions are and what diseases can occur.
What exactly belongs to the middle and inner ear, where exactly are they located?
The inside of the ear begins after 3 to 4 centimeters of ear canal with the eardrum, which separates the outside world from the inside of the ear. This connective tissue membrane measures one centimeter in diameter – behind it lies the air-filled area of the middle ear: the tympanic cavity.
The middle ear
The lenticular tympanic cavity can be thought of as a very small cube with an edge length of about 9.3 millimeters – one “side” is the eardrum, a smaller one is opposite and consists of an oval and a round window, behind which the inner ear is hidden. Between the eardrum and the oval window is a chain of ossicles, namely the malleus, incus and stapes. Three other lateral surfaces consist of bone covered with mucosa. The last side is the opening of the eustachian tube, the
Tuba auditiva. It is a 3.5 centimeter long duct lined with mucosa and connects the middle ear and nasopharynx. This connection opens only when swallowing, yawning or opening the mouth wide – which is important to create equal air pressure between the middle ear and the outside air. Otherwise, the eardrum bulges painfully inward or outward. As the name middle ear suggests, this is located between the outer and inner ear.
The inner ear
The inner ear is located in the middle of the petrous bone, a thick skull bone, and consists of specially shaped bony cavities, the bulbous vestibule, the spiral cochlea, and the three annular semicircular canals (ductus semicirculares) in which the cells and structures of the inner ear are embedded.
The cochlea and arcuate ducts have a common starting point, the atrium of the inner ear. From there, it continues straight to the cochlea, and above the atrium are the three arcuate ducts, which point in all three directions of space, and the sensory cells of the saccule and utriculus.
The bony cochlea is pea-sized, about 3 centimeters long, and has two and a half convolutions. It is filled with fluid and contains a tubular cell structure (organ of Corti) that converts sound waves into nerve signals. The sacculus and utriculus are located in the atrium. They register when our body moves up and down or back and forth. In the three arcades, on the other hand, any rotational movement is sensed and reported to the brain.
