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Question
Draw a well labelled diagram of eye.
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Solution
The adult human eyeball is spherical in shape. The wall of the eyeball is composed of three layers- sclera, choroid and retina.Sclera: It is the external layer composed of dense connective tissue. The anterior part of this layer is called cornea.Choroid: It is the middle layer, bluish in colour and contains many blood vessels. Its posterior two third region is thin while anterior region is thick to form ciliary body. Pigmented and opaque part of ciliary body is known as iris. Anterior part consists of crystalline transparent lens. Aperture surrounded by the iris in front of the lens is pupil.Retina: It is the inner layer and consists of three sub layers- ganglional cells, bipolar cells and photoreceptor cells. The innermost ganglionic cells give rise to optic nerve fibre that forms optic nerve in each eye and is connected with the brain. Photoreceptor cells are of two types- rods and cones. They contain light sensitive proteins called photo pigments. (i) Rod cells- Contain the rhodopsin pigment that are highly sensitive to dim light. They are responsible for scotopic vision. (ii) Cone cells- Contain the iodopsin pigment that are highly sensitive to high intensity light. They are responsible for photopic vision.Optic nerves leave the eye from the median posterior poll of the eye ball. Photoreceptors are absent in this region and hence is called the blind spot. Lateral to the blind spot, a yellowish pigmented spot called macula lutea is present which contains a central pit called fovea. It is the region of greatest visual acuity. The space between the cornea and lens is called aqueous chamber and is filled with aqueous humor. The space between the lens and retina is called vitreous chamber and is filled with vitreous humor.
The adult human eyeball is spherical in shape. The wall of the eyeball is composed of three layers- sclera, choroid and retina.
Sclera: It is the external layer composed of dense connective tissue. The anterior part of this layer is called cornea.
Choroid: It is the middle layer, bluish in colour and contains many blood vessels. Its posterior two third region is thin while anterior region is thick to form ciliary body. Pigmented and opaque part of ciliary body is known as iris. Anterior part consists of crystalline transparent lens. Aperture surrounded by the iris in front of the lens is pupil.
Retina: It is the inner layer and consists of three sub layers- ganglional cells, bipolar cells and photoreceptor cells. The innermost ganglionic cells give rise to optic nerve fibre that forms optic nerve in each eye and is connected with the brain. Photoreceptor cells are of two types- rods and cones. They contain light sensitive proteins called photo pigments. (i) Rod cells- Contain the rhodopsin pigment that are highly sensitive to dim light. They are responsible for scotopic vision. (ii) Cone cells- Contain the iodopsin pigment that are highly sensitive to high intensity light. They are responsible for photopic vision.
Optic nerves leave the eye from the median posterior poll of the eye ball. Photoreceptors are absent in this region and hence is called the blind spot. Lateral to the blind spot, a yellowish pigmented spot called macula lutea is present which contains a central pit called fovea. It is the region of greatest visual acuity. The space between the cornea and lens is called aqueous chamber and is filled with aqueous humor. The space between the lens and retina is called vitreous chamber and is filled with vitreous humor.
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