Human Ear

The human ear is a detailed and complex sensory organ that assists with hearing and balance. It consists of three regions: the outer ear, the middle ear, and the inner ear. Each region works in unison to efficiently collect, amplify, and convert collected sound waves into a nerve signal that the brain can understand. From the human eardrum to the tiny bones in the human ear, each part has a vital function. Understanding the anatomy of the ear will help us to understand how the ear works and how the actual anatomy itself supports balance and hearing.

This guide will help you understand the complete nature of the structural anatomy of the ear and the function of the ear as a whole in a simple process. 

1.0Human Ear Anatomy: Structural Breakdown

External Ear

• Auricle (Pinna):
  An elongated, curved plate of flexible cartilage covered by skin. It has a funnel shape that channels sound waves into the ear canal. This is the visible part in most human ear diagrams.
• External Auditory Meatus:
  The auditory canal is a slightly curved, cartilage and bony canal lined with stratified epithelium, complete with wax-producing glands that trap dust and debris.
• Tympanic Membrane (Eardrum):
  The tympanic membrane, or eardrum, is a thin membrane that vibrates when sound waves hit it. It transfers these vibrations to the middle ear.

Middle Ear

• Tympanic Cavity:
  An air-filled space located behind the eardrum and separated from the inner ear by a bony wall.
• Eustachian Tube:
  A 4 cm long tube connecting the tympanic cavity to the nasopharynx helps equalise pressure on either side of the tympanic membrane. 
• Ear Ossicles:
  The ossicles are three tiny bones: Malleus (hammer), Incus (anvil), and Stapes (stirrup), that amplify the vibrations sent by the tympanic membrane and send them to the inner ear. They are the smallest bones in the human body.

Internal Ear

• Bony Labyrinth:
  The cavity of the temporal bone is a complex structure. It consists of the vestibule, three semicircular canals, and the cochlea. The cavity is filled with perilymph fluid.
• Membranous Labyrinth:
  A fluid-filled system inside the bony labyrinth, containing the cochlear duct, saccule, utricle, and semicircular ducts.  It contains sensory receptors for hearing and balance.

2.0How Does the Human Ear Work?

• Step 1: Sound Wave Collection
  Sound waves in the environment are captured by the auricle (pinna). Its curved, funnel-shaped structure makes it possible to focus and direct these waves into the external auditory canal. 
• Step 2: Eardrum Vibration
  Travelling through the external auditory canal, the sound waves hit the tympanic membrane (eardrum) and cause it to vibrate. The strength and speed of the eardrum's movement depend on the intensity and frequency of the sound.
• Step 3: Amplification by Ossicles
  When sound waves hit the eardrum and create vibrations, they are passed to the three small bones in the human ear by the eardrum: the Malleus, Incus, and Stapes. These three small bones greatly amplify the vibrations.
• Step 4: Conversion in the Cochlea
  Finally, the stapes takes these vibrations and transmits them to the cochlea, which is filled with fluid. Within the cochlear fluid are hair cells that detect movement in the fluid and convert the vibrations into electrical signals.
• Step 5: Signal Transmission
  These electrical signals are transmitted by the auditory nerve to the brain, which interprets them into sounds.

3.0Human Ear: Functions

A. Hearing

B. Balance