Auditory Anatomy

Here we provide a functional description of the human auditory system. In this lab, we focus primarily on the peripheral auditory system, or the portion of the auditory system other than the auditory tissue of the spine and brain.

The human auditory periphery may be divided into three regions:

1. the outer ear, involving the externally visible portion of the auditory system along the ear canal,
2. the middle ear, which transmits sound vibration from the end of the ear canal to the cochlea, and
3. the inner ear, whose primary organ is the cochlea, responsible for transmitting sound information to the nervous system.

Sound enters the auditory system via the outer ear, a diagram of which is shown in Figure 1. The pinna and the concha comprise the externally visible portion of the outer ear, and serve to focus incoming sound waves on the entrance of the ear canal. Upon traveling through the ear canal, these waves then cause the ear drum to vibrate. Next, the middle ear is responsible for transforming ear drum vibration into a similar vibration on the oval window, which is connected to the cochlea. This transformation is performed by an intricate arrangement of three tiny bones, or ossicles: the malleus (or hammer), the incus (or anvil), and the stapes (or stirrup, see Figure 2). Finally, vibration of the oval window causes a wave to travel along the fluid of the cochlea, the function of which is discussed in the following sections.

Figure 1: Diagram of the outer ear (re-printed with permission from [2]).

Figure 2: Diagram of the middle ear (re-printed with permission from [2]).