parts of human eye and its functions
Parts of Human Eye & Their Functions:
The human eye is a ball about 2.5 cm in diameter. It consists of the following parts:
1) Sclerotic: Sclerotic is the outer coating of the eye which is white in colour, that protects the interior of the eye and provides the shape to the eye.
2) Cornea: The front part of sclerotic is transparent to light and is termed as cornea. The light coming from an object enters the eye through cornea.
3) Iris: Iris is just at the back of cornea. This controls the size of the pupil. It acts like a shutter of a photographic camer and allows the regulated amount of light to enter the eye.
4) Eye Lens: Eye lens is a double convex lens with the help of which image is formed at retina by refraction of light.
5) Ciliary Muscles: The eye lens is held by ciliary muscles. Ciliary muscles help the eye lens to change its focal length.
6) Pupil: At the centre of the iris there is a hole through which light falls on the lens, which is called pupil.
7) Aqueous humour : The space between cornea and eye lens is filled with a transparent fluid called aqueous humour.
8) Vitreous Humour: The space between eye lens and retina is filled with a jelly like transparent fluid called vitreous humour.
9) Retins : Retina serves the purpose of a screen in the eye, wherethe images of the objects are formed. Retina is at the back of the eye lens. Retins is made of light sensitive cells, which are connected to the optical nerve.
10) Optic Nerve: Optic nerve carries the information to brain.
11) Principal Axis
12) Blind Spot : The region of eye containing the optic nerve is not at all sensitive to light and is called blind spot. If the image of an object is formed in the blind spot, it is not visible.
13) Yellow Spot : The central part of retina lying on the optic axis of eye is most sensitive to light and is called yellow spot.
14) Eye Lids: Eye lids are provided to control the amount of light falling on the eye. They also protect the eye from dust particles etc.Hope it will be helpful... :)
The given figure shows the structure of the human eye.
The human eye is roughly spherical in shape with diameter of about 2.3 cm. It consists of a convex lens made up of living tissues. Hence, human lenses are living organs contrary to the simple optical lenses.
Thewhite of the eyeis known as thesclera. It is the tough, opaque tissue that protects the outer layer of the eye.Irisis the coloured part of the eye, and thepupilis the black,
The following table lists the main parts of the human eye and their respective functions.
Human eye part
Opens and closes in order to regulate and control the amount of light
Controls light level similar to the aperture of a camera
Protective outer coat
Thin membrane which provides 67% of the eyes focusing power
Helps to focus light into the retina
Covers the outer surface (visible part) of the eye
Provides power to the cornea
Provides the eye its form and shape
Captures the light rays focussed by the lens and sends impulses to the brain via optic nerve
Transmits electrical signals to the brain
Contracts and extends in order to change the lens shape for focusing.
Description and Functions
The cornea is the outer covering of the eye. This dome-shaped layer protects your eye from elements that could cause damage to the inner parts of the eye. There are several layers of the cornea, creating a tough layer that provides additional protection. These layers regenerate very quickly, helping the eye to eliminate damage more easily. The cornea also allows the eye to properly focus on light more effectively. Those who are having trouble focusing their eyes properly can have their corneas surgically reshaped to eliminate this problem.
The sclera is commonly referred to as the "whites" of the eye. This is a smooth, white layer on the outside, but the inside is brown and contains grooves that help the tendons of the eye attach properly. The sclera provides structure and safety for the inner workings of the eye, but is also flexible so that the eye can move to seek out objects as necessary.
The pupil appears as a black dot in the middle of the eye. This black area is actually a hole that takes in light so the eye can focus on the objects in front of it.
The iris is the area of the eye that contains the pigment which gives the eye its color. This area surrounds the pupil, and uses the dilator pupillae muscles to widen or close the pupil. This allows the eye to take in more or less light depending on how bright it is around you. If it is too bright, the iris will shrink the pupil so that they eye can focus more effectively.
These are layers of mucus which help keep the outside of the eye moist. If the eye dries out it can become itchy and painful. It can also become more susceptible to damage or infection. If the conjunctiva glands become infected the patient will develop "pink eye."
These glands are located on the outer corner of each eye. They produce tears which help moisten the eye when it becomes dry, and flush out particles which irritate the eye. As tears flush out potentially dangerous irritants, it becomes easier to focus properly.
The lens sits directly behind the pupil. This is a clear layer that focuses the light the pupil takes in. It is held in place by the ciliary muscles, which allow the lens to change shape depending on the amount of light that hits it so it can be properly focused.
The light focuses by the lens will be transmitted onto the retina. This is made of rods and cones arranged in layers, which will transmit light into chemicals and electrical pulses. The retina is located in the back of the eye, and is connected to the optic nerves that will transmit the images the eye sees to the brain so they can be interpreted. The back of the retina, known as the macula, will help interpret the details of the object the eye is working to interpret. The center of the macula, known as the fova will increase the detail of these images to a perceivable point.
Ciliary body is a ring-shaped tissue which holds and controls the movement of the eye lens, and thus, it helps to control the shape of the lens.
The choroid lies between the retina and the sclera, which provides blood supply to the eye. Just like any other portion of the body, the blood supply gives nutrition to the various parts of the eye.
The vitreous humor is the gel located in the back of the eye which helps it hold its shape. This gel takes in nutrients from the ciliary body, aqueous humor and the retinal vessels so the eye can remain healthy. When debris finds its way into the vitreous humor, it causes the eye to perceive "floaters," or spots that move across the vision area that cannot be attributed to objects in the environment.
The aqueous humor is a watery substance that fills the eye. It is split into two chambers. The anterior chamber is located in front of the iris, and the posterior chamber is directly behind it. These layers allow the eye to maintain its shape. This liquid is drained through the Schlemm canal so that any buildup in the eye can be removed. If the patient's aqueous humor is not draining properly, they can develop glaucoma.
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what is the function of extraocular muscle?
I don't know
how do the lutein and corotenoids help eye protection