Friday, March 07, 2008/12:03 AM
structure of the human eye
hello people(:
Our human eye is the sense organ that gives us our vision. In humans, each eyeball lies in a hollow in the skull known as the orbit and is attached to the skull by rectus muscles. It comprises of three layers, namely the sclera, choroid and retina, all of which have many structures. However, I will first cover on the structures at the front of the eye, which are structures found at the sclera.
Sclera
- It is a tough, white, protective tissue.
- It helps to maintain the shape of the eyeball.
- Muscles which move the eyeball are attached to the sclera.
Cornea
- It is a tough but clear structure.
- It refracts light rays into the eye.
Conjunctiva
Caruncle
Eyelids
Our human eye is the sense organ that gives us our vision. In humans, each eyeball lies in a hollow in the skull known as the orbit and is attached to the skull by rectus muscles. It comprises of three layers, namely the sclera, choroid and retina, all of which have many structures. However, I will first cover on the structures at the front of the eye, which are structures found at the sclera.
Sclera
- It is a tough, white, protective tissue.
- It helps to maintain the shape of the eyeball.
- Muscles which move the eyeball are attached to the sclera.
Cornea
- It is a tough but clear structure.
- It refracts light rays into the eye.
Conjunctiva
- It is a mucous membrane which secretes mucus, therefore keeping the front of the eyeball moist.
Iris
Iris
- It is a circular sheet of muscles which contain a pigment which gives the eye its colour. It has two sets of involuntary muscles in the iris, the circular muscles and radial muscles, which control the amount of light entering the eye.
Pupil
Pupil
- It is a round opening at the centre of the iris.
- It allows light to enter the eye.
Caruncle
- It is a small, red portion at the corner of the eye that contains modified sebaceous and sweat glands.
Eyelids
- They protect the cornea from mechanical damage.
- They can be partly closed so as to prevent excessive light from entering the eye and damaging the light-sensitive tissues inside. This is known as squinting.
- Blinking spreads tears over the cornea and conjunctiva and wipes dust particles off the cornea.
Eyelashes
- They can be partly closed so as to prevent excessive light from entering the eye and damaging the light-sensitive tissues inside. This is known as squinting.
- Blinking spreads tears over the cornea and conjunctiva and wipes dust particles off the cornea.
Eyelashes
- They shield the eye from dust particles.
Tear gland
Tear gland
- It secretes tears which wash away dust particles, keep the cornea moist for atmospheric oxygen to dissolve and lubricate the conjunctiva, thus reducing friction when the eyelids move.
Jia Qian (5) (: