When you think of the ears, the first thing that would usually come to mind would be those two protruding flaps that stick out from either side of the head!
As if that’s all there is to each ear.
But there’s whole hidden world that constitutes the complete ear. And whilst the inner workings are out of sight, the obscured parts of this wonderful piece of apparatus all combine to play an integral role in our ability to hear.
The external outer ear, known as the pinna, is only one element of a complex anatomical structure that enables us to hear all sorts of sounds. The rest of the hearing organ – the inaccessible components – comprise the middle and inner ear, the latter which is buried deep inside the temporal bone on either side of the skull. You can feel the temporal bone – it’s just behind the outer ear. Given that these structural components are so intricate, it is hardly surprising that studying the mechanics of hearing is so tricky.
Here’s how we actually hear
Firstly, sound waves are directed via the pinna through the outer ear channel (external auditory meatus). The waves then hit the eardrum (the tympanic membrane) causing it to vibrate.
Once beyond the eardrum, the sound travels into the middle ear which consists of a small air-filled chamber, home to the three smallest bones in the body, known as ossicles, comprising the malleus, the incus and the stapes. These bones tap against each other and transmit vibrations from the eardrum to the inner ear. Here they cause a pressure wave to propagate in the fluids of the cochlea, a spiral-shaped, fluid filled tube, divided lengthwise by the organ of Corti, the main vehicle of mechanical to neural transduction, which transmits information about the incoming sound to the brainstem.
From there, the signals are projected to the inferior colliculus in the midbrain tectum. The inferior colliculus integrates auditory input with limited input from other parts of the brain and is involved in subconscious reflexes, such as the auditory startle response.
In turn, the inferior colliculus projects to the medial geniculate nucleus where sound information is relayed to the primary auditory cortex in the temporal lobe. It is believed it is here that sound first becomes consciously experienced.
Finally, around the primary auditory cortex lies Wernickes area, the area involved in interpreting sounds that are necessary to understand spoken words.
And there you have it – truly a wonder to behold.
From now on, if you are ever asked by anyone how it is that we hear – you’ll be able to impress with a detailed answer. Alternatively, if the mechanics of hearing is taking a little longer to sink in (understandably), you can find more detailed information at https://www.macmillanihe.com/resources/sample-chapters/9780333993644_sample.pdf