Understanding, Parts - Eyes and Functions

A. UNDERSTANDING EYES

The eye is one of the tools of the human senses that functions as a sense of sight. The eye is a complex sense tool. If we mention Eyes, then in our minds what appears is an eyeball, but actually not only the eyeball plays a role so that we can see, eyelashes, eyebrows, and eyelids also play an important role in supporting vision. Eyes are people whose work is related to light (dark light), color, and objects seen.

B. PARTS OF EYES AND ITS FUNCTIONS

Broadly speaking, the eye has 2 main parts, namely the inside of the eyeball, and the outside of the eyeball.

1. Outer Eye

As I explained earlier, friend, the eye as a sensory tool of vision is not only the eyeball but also the outer part of the eyeball whose function is no less important, namely:

Eyebrows, are the parts that are above the eyelids that are composed of hair - hair, eyebrows function to protect the eyes from water and dirt that want to enter the eyes. For example, the eyes can be protected from perspiration from the eyebrows.

Eyelid, is the part that covers part of the eye, and serves to protect and cleanse the eyes. The eyelids can close and open. The eyelid has a reflex to blink if something happens, for example when the intensity of light received by the eyeball suddenly increases.

Eyelashes, which are parts of the tip of the eyelid which also consist of hair - fine hair. Eyelashes serve to protect the eyes from dirt and also to filter the intensity of light that enters the eye. On the lashes there is a gland called the meibow gland which functions to produce fat to prevent the two eyelids from sticking when flashing.

2. Inside of the eye

a. Eyeball Wall

The eyeball is composed of 3 walls that have a dominant role in carrying out their functions as a means of seeing. The three parts are:

Sklera, is the outer part of the eye wall, this part is white opaque and is hard because it is composed of connective tissue with strong fibers. Skelara serves to wrap and protect the eyeball from damage.

Cornea, at the front of the scera there is a clear part that looks convex, this part is called the cornea. The cornea serves to protect the lens of the eye and pass on the light that enters the eye. The cornea is always moistened with tears, has no blood vessels and is translucent.

Koroid, is part of the wall of the middle layer of the eye that serves as a supplier of oxygen and nutrients to other parts, especially for the retina. In Koroid there are many blood vessels because it is easy to transfer oxygen. Choroid is generally blackish brown or black. The dark color of the choroid functions so that light is not reflected (reflected). The front part of the choroid which is cut off will form the iris (the rainbow membrane), in the middle of the iris there is a hole called the pupil.

Retina, is the inner wall of the eye that serves to capture the shadow of an object because it has cells that are sensitive to light. Retina is a part that has a light receptor consisting of nerve cells, namely:

Stem Cells (Basilus),

is a cell that is sensitive to light is not strong (more important at night or in the dark)

Cone Cells (Conus),

is a cell that is sensitive to strong light intensity (more active during the day or in bright conditions)

The back of the retina has neither stem cells nor cones, therefore it is called a blind spot, and if the shadow of an object falls at that point then we cannot see. Whereas the part of the eye that has many cone cells is called the yellow dot, this part is the most sensitive part to light, when the shadow of an object falls on the yellow dot, then humans are able to see clearly.

b. Iris

Iris is the part that gives color to the eyes, maybe a friend has ever seen someone whose color is brown, black, blue or green? Now the iris has the role to give color to the human eyeball. In the Iris there are color pingmen, therefore the iris is often called the rainbow membrane, the iris is located on the front of the eyeball. The iris can shrink and expand, the iris serves to regulate the movement of the pupil according to the intensity of the incoming light.

c. Pupil

The pupil is the part of the hole in the middle of the iris that serves to regulate the amount of light entering the eye. The pupil will widen when a little light enters the eye (in a darker state), and will shrink when a lot of light enters the eye (in the increasingly brighter state). The process of enlarging and shrinking pupils is useful so that the incoming light is not excessive and not too little so that we can still see well.

d. Lens

The lens is a soft and transparent part that is located behind the iris. The lens serves to collect and focus the light so that the shadow of the object falls in the right place. The lens has an ability called accommodation power, namely the ability to thicken / thin out or bulge / flatten the lens according to the distance of the object being seen. The lens is bound by the lens holder's muscle, this muscle that functions in the ability of Lens Accommodation Power. If the lens will be more convex when you see objects that are close and increasingly flattened when you see objects that are far away.

e. Lakrima gland (tear gland)

Lakrima gland is a part of the eye that functions to produce tears that will wet the cornea, protect the eyes from germs, keep the eyes and inner eyelids soft and healthy.

f. Optic nerve

The optic nerve is the part that serves to provide visual information that is received and forwarded to the brain.

g. Blind Point

Blind point is the part that serves to continue and deflect the nerve file to the brain. At the blind spot there are no cells that are sensitive to light stimulation. Therefore if the shadow of an object falls in this part, then we cannot see.