Two purposes are served by the blinking of the eyelids. One is to keep it from drying out and the other is to cleanse it and keep it fee from dust and other harmful substances.
Lubricants are secreted from 20 to 30 sebaceous oil producing glands lined around our eyes. When we blink the opening and closing lubricate the eyeball by the secreted lubricants and thus protect the eye from drying. The blinking is done so rapidly that it does not impair our vision.
The cleansing is done by the tears that are secreted by the tear glands. The tears wash away the dust and other harmful material that may have accumulated on the surface of the eyeball.
The snake does not have any eyelids and as such cannot blink. But it has a hard scale over its eyes to protect them form harm.
The camel has long eyelashes also so as to protect it from sand from sandstorms.
No comments:
Post a Comment