Welcome to Zoology World

balindrakumar033@gmail.com   22/06/2018,Friday


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 eyeball

Eyeball is made up of 3 coats or tunic.

Eye is made of three layer

1. Sclerotic layer(Fibrous tunica)

sclerotic layer

Outer most and opaque,fibrous and non-vascular layer easily seen as white of the eye.It is a coat of desne connective tissue made up of collagen fibres and firbroblastic .Sclera covers entire eyeball except cornea, gives shape to eyeball.Sclera in frog is cartilaginous.

a. Cornea

Cornea is transparent layer

In the centre,sclerotic layer it merges with the transparent round window called cornea.


The cornea and exposed part of sclera are covered externally by a thin, transparent membrane the conjunctiva.

Conjunctiva is thin transparent membrane

2. Choroid layer( Vascular tunica)

choroid layer(Vascular tunica)

Choroid also known as uvea middle.It is vascular layer which supplies nutrients to the eye.It is distinguished into part choroid,cilliary body and iris.

a. Choroid

It is highly vascular posterior portion of vascular tunica.The choroid occurs in the main part of eyeball adhered to the sclerotic. (The pigment is reddish in rabbit and black,brown or bluish in man).

b. Ciliary body

Ciliary body is vascular
pigment muscles of eye

Ciliary body is vascular and pigmented like choroid,made up of ciliary processes and ciliary muscles(only circular type).The ciliary body is hidden by iris. The ciliary body helps in accommodation by altering the focus of eye from object or the shape of lens near or far vision.


Ciliary body is vascular
pigment muscles of eye

Beyond the ciliary body, the vascular tunic sharply turns inwards,forming a circular ,shelf-like diaphragm called iris.The colour of the iris is responsible for colour of eye eg.brown,black,blue or green.In albinos,iris is deficient of pigment.

What is Lens