Welcome to Zoology World

balindrakumar033@gmail.com   25/11/2017,Saturday

WELCOME TO ZOOLOGY WORLD

The science or study of animal life. Together with botany, the study of plant life, it forms the science of biology. Zoology is such a vast subject that most zoologists specialize or focus on the study of particular organisms or taxonomic groups. tion of animals.

Human
eye is the most important role play in vision

Human eye

Human eye have binocular vision.The eye can discriminate colour,appraise length,width and depth visually and form true inverted image.

Structure of eye

The eye are two in number and lodged in orbits(bony socket) of skull. The eye is a hollow ,spherical organ,about 2.5cm in diameter and about 6 to 8 gram in weight.It has two parts-

Protective devices

Eye has four protective devices.

Eye brows

Man has two eye 
brows which prevent the sweat and rain drop to in eye

The outwardly directed hair of the eyebrows carry the sweat and rain drops trickling down the forehead to the sides to prevent their falling into the eyes

Eye lids(Palpebrae)

 In man two eyelids are present,upper is movable.They are regularly closed 
at short  intervals to clean the cornea.This is called blinking.

In man two eyelids are present,upper is movable.They are regularly closed at short intervals to clean the cornea.This is called blinking. In frog out of two upper eyelid is immovable and lower eyelid is movable. Nictitating membrane is present in frog which protect eye in water . Movement of nictitating membrane tekes place by retractor bulbi.It becomes folded by levator bulbi.

A nonfunctional vestigeal nictitating membrane,called plica-semilunaris, occurs in human eyes. It remains permanently retracted at the inner angle of each eye.

Eye lashes

The eyelids bear at the free edge a row of stiff hair, the eye lashes. These check the entry of dust particles, tiny insects and rain drops into the eyes.

Eye lashes helps
to prevent dust partcles ,insect to come in eyes

Eye glands:-

a. Meibomian gland

Meibomian 
gland act as a lubricant

The eye-lids bear at the free edge a row of meibomian gland that is modified sebaceous gland.(Act as a lubricant).

Lacrimal gland or Tear gland

Lacrimal gland is tear 
gland which help in moisture of eyeball

It lies in the upper outer part of the orbit and secretes a slightly saline, watery fluid that contains a bacteriolytic enzyme name lysozyme.This secretion moistens the surface of the eyeball.The excess of this secretion passes through nasolacrimal duct.It is modified sweat gland.

Harderian gland

Some aquatic mammals(whale) possess harderain gland which lubricate nictitating membrane.It is also found in frog and birds.

Harderian gland
helps the lubrication of nictitating membrane of some aquatic mammals
d. Gland of zeis(zis)
gland of zeis

These are modified sebaceous gland,found at base of hair follicle of eye lashes,pour lubricating fluid in hair follicle.Infection of these glands is Sty.

Eye ball