The curves of the Pinna (the outside of the ear, what we can see) direct sound waves into the Ear Canal. They rumble against the Ear Drum (Tympanic Membrane), which sends vibrations through three tiny bones called Ossicles, that transmit to the Cochlea. The Cochlea is able to detect pressure sensations and convert them to electrical impulses, which get carried by Nerves to the Brain, which finally interprets the sound.
The Pinna and Ear Canal comprise the “External Ear,” which terminates at the Ear Drum (Tympanic Membrane). On the other side of the Ear Drum, the three Ossicles sit in a tiny space called the “Middle Ear“. The “Inner Ear” begins at the Labyrinth and Cochlea; the former, a.k.a. Vestibular System, controls our balance. When clinicians examine your ear with the common instrument called an “otoscope,” we can see from the External Ear up to the Ear Drum. Changes in the Ear Drum can give us information about what’s happening in the Middle Ear. We can’t tell anything at all about the Inner Ear by looking.
Other structures are noted in the Figure:
- The Eustachian Tube runs from the Middle Ear to the back of our Nasal Passage. It serves to maintain a normal air pressure within the Middle Ear.
- The Labyrinth, sitting next to the Cochlea in the Inner Ear, helps maintain balance. It’s filled with fluid and tiny nerve endings, transmitting constant signals to the Brain every time our head moves or tilts.
- The Mastoid Bone is the name for the part of the skull where the Ear is located.
Various conditions can affect the ear. Infections in the ear canal (external ear) are called Otitis Externa; in the middle ear they’re called Otitis Media (this is the kind young children commonly get). The ear canal can get clogged with wax (Ceruminosis), causing ear pain / discomfort, and/or hearing loss (other things that can plug up the canal include cotton from Q-tips, and insects). Eustachian Tube Dysfunction can cause ear pain and hearing changes due to increased middle ear pressure, but that’s usually more of a discomfort than ear infection pain is. It occurs when nasal problems block it where it connects with the nose (not shown in the diagram), such conditions of the nose include allergies (Allergic Rhinitis), the Common Cold, Nasal Polyps, or Sinusitis (most people who complain about their “sinuses acting up” really have Allergic Rhinitis). Rare infections of the mastoid bone are called Mastoiditis.
A variety of inner ear diseases can cause vertigo (room spinning) if they involve the labyrinth or its nerve (see our topic Dizziness). Diseases which affect the cochlea or its nerve cause Hearing Loss or ringing in the ear (tinnitus). This kind is called “Sensorineural Hearing Loss”, since it involves nerve signals. “Conductive Hearing Loss” comes from diseases of the middle ear (infections, tumors) or the ear canal (infections, wax, tumors), which impede air conduction