Elementary structure and function of eye and ear

Introduction

The human eye and ear are the most vital organs of the human body. A person cannot see the natural beauty of the environment without the eye and can’t listen to the voice of the beautiful creatures on the earth without ears. So, in the elementary structure and function of the eye and ear, we will study the basic structure of the human eye and the ear. 

Elementary structure and function of eye and ear definition

In the human body, there are five sensory organs: the eyes, nose, ear, skin and tongue. Human eyes and ears have bilateral symmetry and are located on both sides of the human face. The human eye and ear have the most significant role in life. We cannot see the beauty of nature like mountains, rivers, forests, sky, sun, etc. without the eye and we cannot hear the voice of nature like the melodious sound of birds, the sound of rain, the voice of other persons, etc. No one can explain this beautiful feeling to anyone. We can say that sound and sight are the 2 most glamorous senses we possess. It is quite necessary to study the structure and function of the human eye and ear.

Structure of Human Eye

We have learned that objects are visible because of the light reflected from their surfaces. These reflected lights enter our eyes, and we see that object. The human eye is spherical. The outermost layer of the eye is the cornea; it is white in color and transparent, allowing light to pass through it. The cornea refracts or bends the light when it passes through it. It acts as a tough front wall of the eye and protects the interior part of the eye from accidents.

Behind the cornea, there is a dark, muscular structure called Iris. It determines the color of the eye. There is a small opening in the center of the Iris for the light to enter; it is known as the pupil. The Iris actually acts as a shutter of a camera. It controls the amount of light entering the eye by enlarging or shrinking and thereby adjusting the size of the pupil.

For example, when we directly focus on the light from the torch in the human eye, the Iris shrinks. This is because the intensity of light is too much for the eyes to bear. The shrinking Iris stops the unwanted light from entering through the pupil.

Alternatively, when we are in a dark room, it expands, allowing more light to enter through the pupil.

The light which enters through the pupil passes through the convex lens, which is present behind the pupil. A convex lens has a converging property, thicker at the center than the edges. It focuses all the light at a single point.

The area where the image is formed is known as the retina; it contains lots of nerve cells that sense the light. The nerve cells are of two kinds: cones sensitive to bright light and rods sensitive to dim light.

The message is then sent to the brain through the optic nerve.

 Mechanism of vision-WORKING OF EYES

 Light rays emitted by any object enter the eye. A small, real and inverted image of an object is formed at the retina. Sensory cells of the retina are sensitized and the optic nerve carries this impulse to the brain. At this time the animal is able to see the object.

 Cornea, aqueous humor and biconvex lens completely refract the light rays coming from the object. As a result of this an inverted image is formed at the retina. Just like the diaphragm of a camera, the iris of the eye decreases or increases the diameter of the pupil according to light. Iris expands to decrease the pupil in high intensity of light so a small amount of light touches the retina.

Defects in Human eyes

Like other parts of the human body, our eyes are also affected by some diseases. The disease is mentioned below:-

• Nearsightedness or Myopia: It is the condition in which a human cannot see the far object clearly but can easily see the nearby thing.
• Long Sightedness or Hypermetropia: It is the condition in which a human cannot see the nearby object clearly but can easily see the farby thing.
• Presbyopia: It is a combination of both myopia and hypermetropia. In this condition, a person cannot see the nearby and far objects. It generally happens in old age.
• Cataract: It is the condition when clouding in the lens takes place. A small surgery can cure it.

Structure of Human Ear

The human ear is the organ whose primary function is to hear a sound and detect and analyze the noise. In some mammals like human beings, it is also used for the sense of balance.

The compression in the air results in the sound in our brain. The compression in the air has to be converted into an electrical signal for our brain to detect.

The human ear is made up of three components: the outer ear, middle ear and inner ear.

• The outer ear has a fitnah or ear canal or auditory canal.
• The middle ear has an eardrum and the three ossicles named hammer, anvil and stirrup, which means anchor, Milius and strippers.
• The inner ear includes semicircular canals connected to the cochlea and the auditory system.

 Mechanism of hearing

The compression in the air reaches the outer ear called the pina, which directs the sound to travel through the ear canal to reach the eardrum or tympanic membrane. Due to this comparison, the membrane starts vibrating. This steel membrane vibrates and relaxes depending on the compression amplitude in the air. The vibration then passed to the three bone-in the ears connected to the eardrum hammer, anvil, and stirrup and then amplified twenty times than actual vibration after the amplification of the ear bone. This vibration through the oval ear is called the cochlea. The electric signals from the cochlea are sent to the brain through the auditory nerves. Then the brain reads the electric impulses and detects them as a sound.

Conclusion

In the above chapter, we have studied the Elementary structure and function of the eye and ear examples. We all are well aware that our five senses are the most wonderful gift given to us by god. These five things consist of the ear, skin, tongue, ear and nose. We have studied the mechanism of the seeking thing by eyes and the mechanism of hearing by ears. This is one of the most important topics from the examination point of view.