The ear - anatomy, how it works and diseases

The ear is one of the human sensory organs. It picks up noises, tones and sounds and extends from the concha, which is visible on the outside, via the auditory canal, eardrum and ossicles to the cochlea, which has the sensory cells for perceiving sound.

Anatomy of the ear

The human ear (auricle) is used to pick up acoustic sound stimuli. It is made up of three anatomical regions. These are

• the outer ear (auris externa)
• the inner ear (auris interna)
• the middle ear (auris media)

The outer ear consists of the auricle (Auricula auris), the external auditory canal (Meatus acusticus externus) and the eardrum (Membrana tympani). The auricle also includes the earlobe.

© bilderzwerg / Fotolia

External auditory canal

The external auditory canal is a section of cartilage that transitions into a section of bone. It has a length of 3 to 3.5 centimetres and is approx. 0.5 centimetres wide. The skin of the ear canal contains sebaceous glands, sweat glands and hair follicles. The glands secrete earwax (cerumen). The yellowish, sticky secretion is responsible for cleaning the ear canal and ensures that no dust, dirt or water can enter the ear.

Middle ear

The middle ear is made up of a pneumatized cavity within the temporal bone called the tympanic cavity (cavum tympani). Structures such as the ossicles, nerves, blood vessels and the eardrum are also part of the middle ear. The eardrum is a membrane that separates the auditory canal from the middle ear. The eardrum has a thickness of 0.1 millimeters and a diameter of between 9 and 11 millimeters. Another component is the auditory tube.

Inner ear

The membranous labyrinth forms the inner ear. It is embedded in a bone cavity in the petrous pyramid. In the inner ear, a distinction is made between the vestibular organ and the cochlea. While the vestibular organ is responsible for the sense of balance, the cochlea forms the basis for the sense of hearing.

The labyrinth is filled with endolymph, a fluid rich in potassium. The most important structures of the labyrinth include thecochlear duct, the sacculus, theutriculus and the three semicircular canals.

Humans can hear through the ear, i.e. perceive noises and sounds. Hearing is an extremely complex process: sound waves pass through the pinna and the external auditory canal. At the end of this is the eardrum, which they cause to vibrate slightly when they hit it. The tiny auditory ossicles transmit these vibrations within the tympanic cavity to the membrane of the oval window at the beginning of the inner ear. A fluid stored there then transmits the movement to tiny hair cells, which convert it into nerve impulses. These impulses can then be transmitted to the brain.

The ear also contains the organ of balance, which works in a similar way. With the help of the organ of balance, people can keep their balance and stand upright even with their eyes closed.

Common ear diseases

The human ear can be affected by various diseases. For example, the pinna is very susceptible to infections caused by bacteria or fungi. As a result, there is a risk of ear infections (otitis externa), which occur frequently. Without medical treatment, there is a risk of the infection spreading to the bone.

Otitis externa

One of the most common ear diseases is otitis media, which is accompanied by symptoms such as earache. Doctors differentiate between acute and chronic otitis media. Sometimes the inflammation also spreads to the ossicles and destroys them.

Damage to the middle ear can also be caused by high sound pressure , such as an explosion. In medicine, this is referred to as a blast trauma.

Tinnitus

Tinnitus is another common ear condition. This involves noises in the ear such as buzzing, whistling, ringing or humming, which are only perceived by the person affected. There is no external cause for the noises. Possible triggers include sudden hearing loss, taking certain medications, stress or various illnesses. It is not uncommon for no cause at all to be found for the complaints.

Other ear diseases are:

• Hearing loss such as conductive hearing loss or sensorineural hearing loss
• Otosclerosis (stiffening of the auditory ossicles)
• hyperacusis, in which those affected suffer from hypersensitivity to noise
• Injuries to the eardrum caused by external force

© Vladimir Voronin / Fotolia

Diagnosis of ear diseases

The diagnosis of ear diseases depends on the cause. If hearing loss is suspected, the ear specialist will carry out a hearing test to determine its extent. In the case of a middle ear infection, an otoscope (ear mirror) is used for an examination. This allows reddening of the eardrum to be detected.

Ear hygiene and prevention

When cleaning the ear, it is advisable not to use cotton buds. The use of cotton buds promotes the formation of an ear plug, which impairs hearing. They can also damage the sensitive eardrum.

What is harmful to the ears?

Constant noise, such as loud music in discos, at concerts or through headphones, is particularly harmful to the ears. But constant noise at work also impairs hearing.

Be careful with ear jewelry and piercings

Caution is also advised when wearing ear jewelry or piercings. There is a risk that the fashionable outfit or pierced ear holes could trigger inflammation or allergic reactions.