The incus, in turn, articulates with the stapes. The middle ear consists of a space with three small bones called the malleus, incus, and stapes, the Latin names that roughly translate to “hammer,” “anvil,” and “stirrup.” The malleus is attached to the tympanic membrane and articulates with the incus. The auricle, ear canal, and tympanic membrane are referred to as the external ear. At the end of the ear canal is the tympanic membrane, commonly referred to as the eardrum, that vibrates after it is struck by sound waves. The C-shaped curves of the auricle direct sound waves toward the ear canal. The large, fleshy structure on the lateral aspect of the head is known as the auricle. See Figure 8.15 for an image of the anatomy of the ear. Hearing is the transduction of sound waves into a neural signal by the structures of the ear. These nerve cells of the retina leave the eye and enter the brain via the optic nerve (cranial nerve II). The cones are sensitive to different wavelengths of light and provide color vision. ![]() Two types of photoreceptors within the retina are the rods and the cones. The innermost layer of the eye is the retina that contains the nervous tissue and specialized cells called photoreceptors for the initial processing of visual stimuli. ![]() The cornea can be reshaped by surgical procedures such as LASIK. The cornea, with the anterior chamber and lens, refracts light and contributes to vision. The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. The iris constricts the pupil in response to bright light and dilates the pupil in response to dim light. The iris is a smooth muscle that opens and closes the pupil, the hole at the center of the eye that allows light to enter. ![]() The conjunctiva extends over the white areas of the eye called the sclera, connecting the eyelids to the eyeball. The inner surface of each lid is a thin membrane known as the conjunctiva. The eyelids, with lashes at their leading edges, help to protect the eye from abrasions by blocking particles that may land on the surface of the eye. See Figure 8.1 for an illustration of the eye. The eyes are located within either orbit in the skull. Our sense of vision occurs due to transduction of light stimuli received through the eyes.
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