Human ear, organ of hearing and equilibrium that detects and analyzes sound by transduction (or the conversion of sound waves into electrochemical impulses) and maintains the sense of balance (equilibrium).
The human ear, like that of other mammals, contains sense organs that serve two quite different functions. That of hearing and that of postural equilibrium and coordination of head and eye movements. Anatomically, the ear has three distinguishable parts: the outer, middle, and inner ear. The outer ear consists of the visible portion called the auricle, or pinna, which projects from the side of the head, and the short external auditory canal, the inner end of which is closed by the tympanic membrane, commonly called the eardrum. The function of the outer ear is to collect sound waves and guide them to the tympanic membrane.
The middle ear is a narrow air-filled cavity in the temporal bone. It is spanned by a chain of three tiny bones—the malleus (hammer), incus (anvil), and stapes (stirrup), collectively called the auditory ossicles.
This ossicular chain conducts sound from the tympanic membrane to the inner ear, which has been known since the time of Galen (2nd century CE) as the labyrinth. It is a complicated system of fluid-filled passages and cavities located deep within the rock-hard petrous portion of the temporal bone. The inner ear consists of two functional units. The vestibular apparatus, consisting of the vestibule and semicircular canals. Which contains the sensory organs of postural equilibrium. And the snail-shell-like cochlea, which contains the sensory organ of hearing. These sensory organs are highly specialized endings of the eighth cranial nerve, also called the vestibulocochlear nerve. Read full article by by Pritish Kumar.
Ear Anatomy – Outer Ear
outer ear diagramThe outer ear comes in all types of shapes and sizes. This structure helps to give each of us our unique appearance. The medical term for the outer ear is the auricle or pinna.
The outer ear is made up of cartilage and skin. There are three different parts to the outer ear; the tragus, helix and the lobule.
The ear canal starts at the outer ear and ends at the ear drum. The canal is approximately an inch in length. The skin of the ear canal is very sensitive to pain and pressure. Under the skin the outer one third of the canal is cartilage and inner two thirds is bone.
The ear drum is about the size of a dime and is the same size in the new born baby as in the adult. The medical term for the ear drum is the tympanic membrane. The ear drum is a transparent gray membrane. Attached to the center part of the drum is the middle ear bone (the malleus).
Ear Anatomy – middle ear
The space inside the ear drum is called the middle ear. Three of the smallest bones of the body are found in the middle ear; they are called the malleus, the incus and the stapes. These bones are also known as the hammer, anvil and the stirrup. The medical term for all three bones together is the middle ear ossicles.
Ear Anatomy – Inner Ear
Next to the middle ear in the bone of the skull is a small compartment which contains the hearing and balance apparatus known as the inner ear. The inner ear has two main parts. The cochlea , which is the hearing portion, and the semicircular canals is the balance portion.
The cochlea is shaped like a snail and is divided into two chambers by a membrane. The chambers are full of fluid which vibrates when sound comes in and causes the small hairs which line the membrane to vibrate and send electrical impulses to the brain.
The semi-circular canals are also known as the labyrinthine. These little canals are lined up at right angles (90°) to each other. This allows the brain to know in which direction the head is moving. These semi-circular canals are filled with fluid and have some small calcium crystals embedded in the lining.
Coming from the inner ear and running to the brain is the eighth cranial nerve, the auditory nerve. This nerve carries both balance and hearing information to the brain. Along with the eighth cranial nerve runs the seventh cranial nerve. The seventh cranial nerve is also known as the facial nerve because it supplies nerve impulses to the muscles of the face.
How do you hear?
Hearing starts with the outer ear. When a sound is made outside the outer ear, the sound waves, or vibrations, travel down the external auditory canal and strike the eardrum (tympanic membrane). The eardrum vibrates. The vibrations are then passed to 3 tiny bones in the middle ear called the ossicles. The ossicles amplify the sound. They send the sound waves to the inner ear and into the fluid-filled hearing organ (cochlea).
Once the sound waves reach the inner ear, they are converted into electrical impulses. The auditory nerve sends these impulses to the brain. The brain then translates these electrical impulses as sound.