The structure of the ear is as complicated as its function. The sound of rustling leaves, a ticking clock or birds singing is safe. The ear is adapted to much louder sounds, but too often contact with them can be dangerous to your he alth. Find out how the ear is built.
The structure of the earis really complicated. When we stand in front of the mirror, we see only a fragment of the organ responsible for the sound perception of the world. This part isauricle- this is where theouter earstarts. Behind him ismiddle ear , and furtherinner ear . When they are properly built, they work well and are able to cooperate with the cerebral cortex, which interprets what reaches it through the ears, we can say that we hear.
Outer ear: structure
The outer ear is the pinna and the outer ear canal. Hardly anyone is satisfied with the shape of the auricle, but we have little influence on it, because we inherit its appearance. It grows with us up to the age of 18. Its shape resembles an elongated, bent plate. It is made of flexible cartilage covered with skin, and if you look at the external auditory canal, you would notice that it is a few centimeters long and slightly twisted. It is for this reason that the ENT specialist must "straighten" the tube in order to look inside the ear, pulling the pinna up and back. The ear canal is covered with skin. Short, thick hair grows at the very beginning. The secretion of their sebaceous glands, mixed with exfoliated epithelium, forms earwax. When too much of it accumulates, it clogs the ear canal. Then we hear worse, sounds reach us as if through cotton wool. Remember not to remove the earwax yourself with cotton sticks, because we just push the plug inside. In addition, we can damage the eardrum that closes the external auditory canal. The only sensible method of removing earwax is to rinse the ear by an ENT specialist. The tympanic membrane is oval in shape, approx. 10 x 8.5 mm in size and approx. 100 microns thick. It is covered with epithelium from the outside and mucosa from the inside. It is tense, strong and can withstand a pressure of about 100 cm of mercury. When a sound (a wave of vibrating air) enters our ear, it hits the eardrum andmakes it vibrate.
Middle ear: structure
It starts right behind the eardrum. First, it is a small cavity that is lined with a mucosa and filled with air. Its side touches the so-called the mammary cavity. If we touch the skull behind the auricle with a finger, we feel a small mound. This is the mammary bone inside which this cavity is located. The ear perceives the acoustic waves of the air, but also the tremors of the skull bones. So you can also talk about the so-called bone conduction of sound. When a phoniatrist examines our hearing, incl. checks bone conduction by applying a special device to the mammary bone.
Vibrations of the eardrum are transmitted to the inner ear through a chain of three auditory ossicles, gracefully named hammer, anvil, and stapes, held in place by muscles and ligaments. First, the hammer, attached to the eardrum, receives and transmits vibrations to the anvil, and it - to the stapes. The latter delves into the so-called atrium window and sets in motion the fluid filling the atrium (the so-called endothelium).
As we already know, the tympanic cavity is filled with air. The Eustachian tube (the Eustachian tube) is used to equalize the pressure on both sides of the sealed eardrum. This longitudinal channel from the tympanic cavity runs in the temporal bone as far as the nasopharynx. When the throat and nose are inflamed, the mucosa swells and sometimes the eustachian tube closes. Then the pressure in the tympanic cavity is not equalized and we hear worse. This also happens, for example, during the landing of an airplane, when the air pressure in the cabin increases. Yawning or swallowing saliva may then help us, which causes the flexor muscle of the soft palate to contract, and this opens the pharyngeal opening of the Eustachian tube. The air flows through it into the tympanic cavity and equalizes the pressure with that in the aircraft cabin. And we hear well again. Sour candies are distributed on airplanes for a long time. They increase the secretion of saliva, which you have to swallow frequently, so they can prevent you from "deaf".
ImportantSound intensity is measured in decibels. Our ears are very sensitive to them. We perceive some sounds as pleasant, others may damage our hearing. What situations are safe for our ear, which are risky and which are dangerous?
- 20-60 decibels are safe sounds, e.g. rustling leaves, ticking clock, noise of a quiet street, ordinary conversation, birds singing,
- 75-100 decibels are risky sounds, e.g. buzz in a restaurant with music, noise of a loud street, the sound of a moving truck and a bus, a working lawn mower engine,
- 100-140 decibels ismenacing noise, e.g. motor whirr without a muffler, disco and rock concert sounds, working jackhammer, jet plane taking off.
Inner ear: structure
It consists of a vestibule, a cochlea and semicircular canals. The vestibule is located just behind the hearing aids. Three semicircular canals depart from it slightly upwards. They resemble hoops set in three different planes perpendicular to each other. The so-called The cochlea, responsible for receiving auditory stimuli, is a bone canal about 35 millimeters long, which resembles the shape of a vine snail shell. In it is a membranous cochlear duct filled with fluid (endothelium). In turn, the so-called a spiral organ with numerous sense cells. These are the endings of the eighth cranial nerve fibers. Sound vibrations transmitted through the eardrum and ossicles to the atrium window reach the endothelium of the cochlea duct through the fluids filling the atrium. Here, the sensory cells of the spiral organ convert them into electrical impulses. The impulses run along the eighth nerve to the temporal lobes of the brain. This is where they are analyzed by the cerebral cortex. The cerebral cortex, firstly, remembers individual impulses, and secondly, assigns specific meanings to them. This allows us to understand spoken words and distinguish the roar of a cow from a cello concert.
ImportantWhat's your hearing
- good to hear a whisper from 6 meters away,
- weak when you hear a whisper from 1-4 meters away,
- dull when you hear a whisper up to 1 meter away,
- you are at risk of becoming deaf when the person speaking to you has to bend close to your ear.
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