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00:00hi kids today we will learn about one of our sense organs that is our eyes so
00:09let's start eyes eyes a very important sense organ that gives us vision we can
00:18see in bright as well as dim light but we cannot see when there is no light at
00:26all we use our eyes in almost everything we do from reading writing eating
00:36drinking dancing watching playing and many more now let's learn internal as
00:46well as external parts of the human eye the human eye is a delicate organ that
00:54is protected by the hard bony socket in the skull it is a ball-shaped organ but
01:05we see only a small part of it and that we call as our eye but actually it is a
01:14ball shape now let's first see the visible part of our eyes eyebrows this
01:23is not a part of I but it keeps the moisture sweat rain from running down a
01:30person's forehead straight into the eye eyelids these are our eyelids it is a
01:39thin fold of skin on the eyes that helps to open and shut the eyes and also
01:47protects the eyes from the dust and other particles it also spreads tears
01:55and other secretions in the eye to keep the eyes moist the reflex action of
02:04blinking protects the eyes from anything that suddenly comes closer to the eyes
02:13eyelashes these are our eyelashes these are hairs that grow on the edges of the
02:21eyelids eyelashes to protect the eyes from any dust or foreign particles iris
02:34is a round colored part of the eye pupil an even smaller round portion inside the
02:44iris is called pupil this white part that we see is called sclera so these
02:54are the external parts that we see now let's learn the internal structure of
03:00the eye our eye is a spherical structure it has a bulging part in the
03:10center of its front side and it's called cornea cornea is thin shiny transparent
03:19convex cover over the round color part of the eye I repeat cornea is a thin
03:29transparent convex cover over the round colored part of the eye light enters the
03:40eye through this cornea iris iris is the round colored membrane just behind the
03:50cornea it's the iris that imparts color to the eye it can be gray it can be
04:00brown it can be black it can be blue which has a small circular opening in
04:07the middle and it's called pupil pupil it is a dark center in the middle of the
04:15iris pupil is a small circular opening in the center of the iris it's the pupil
04:26that regulates the amount of light entering the eye it changes its size to
04:34regulate the amount of light entering the eye when there is bright source of
04:42light iris makes a pupil contract so that less amount of light enters the eye
04:50and when the source of the light is very dim iris makes a pupil expand or dilate
04:59so that more amount of light enters the eye now which part of the eye is called
05:06eye lens the lens is convex in shape and is made up of transparent jelly like
05:15material that focuses light into the retina in a healthy eye the lens changes
05:24its shape to adjust for close or distant vision but as we age the lens tends to
05:34get hardened and its adjusting power is limited ring-shaped ciliary muscle
05:42surrounds this lens and the ciliary muscle contract or relax to adjust the
05:50shape of the lens according to the visual need wall of the eye excluding
05:58the area of cornea is made up of three different layers the outermost layer is
06:05called sclera it is tough protective sheet white in color and is known as
06:13white of the eye middle layer is called choroid it is a vascular layer the
06:23innermost and third layer is called retina it is on this layer on which the
06:31image is formed it is light sensitive and like the screen of a camera retina is
06:40made up of two types of receptor cells rod cells and cone cells rod cells are
06:52sensitive to dim light that is they work in dim light and they don't provide us
06:59colored vision so in case of dim light we are not able to see anything in color
07:06we see everything gray or black and white when it's dim light next are the
07:16cone cells cone cells are sensitive to bright light and they provide us colored
07:23vision so we see everything colorful in bright light so remember in dim light
07:34rod cells work and when it's bright light cone cells work cone cells provide
07:42us colored vision vitreous vitreous is the clear jelly-like material that fills
07:51the hollow center of the eye that is between the lens and the retina aqueous
08:00aqueous is also a liquid that fills between the cornea and the lens now next
08:09part that we will learn is optic nerve optic nerve is a nerve that transmit the
08:18image from the eye to the brain and it's the brain that will interpret the message
08:25and we will be able to see any object so kids today we have learned the internal
08:34as well as external parts of the eye we will learn about the working of the eye
08:40in our next assignment now you may go ahead and take a quiz to learn more