Sclera

 Thus clearer also known as the white of

the eye is the opaque fibrous protective

outer layer of the eye containing

collagen and elastic fiber in humans the

whole scarer is white contrasting with

the colored iris but in other mammals

the visible part of the sclera matches

the color of the iris so the white part

does not normally show in the

development of the embryo.

The scarer is

derived from the neural crest in

children it is thinner and shows some of

the underlying pigment appearing

slightly blue in the elderly fatty

deposits on the scarer can make it

appear slightly yellow the human eye is

relatively rare for having an iris that

is small enough for its position to be

plainly visible against the scarer this

makes.

It easier for one individual to

infer where another individual is

looking under cooperative eye hypothesis

suggests this has evolved as a method of

nonverbal communication structure the

scarer forms the posterior 5/6 of the

connective tissue coat of the globe it

is continuous with the dura mater and

the cornea and maintained the shape of

the globe our offering resistance to

internal and external forces and

provides an attachment for the extra

ocular muscle insertions the scarer is

perforated by many nerves and vessels

passing through the posterior scarole

foramen the hole that is formed by the

optic nerve at the optic disk the outer

two thirds of the sclera continues with

the dura mater V of the dural sheath of

the optic nerve the inner third joins

with some choroidal tissue to form a

plate across the optic nerve with

perforations through which the optic

fibers pass the thickness of the scarer

varies from 1 millimeter at the

posterior pole to 0.3 millimetres just

behind the rectus muscle insertions the

scarers blood vessels are mainly on the

surface along with the vessels of the

conjunctiva those in the episteme

a render the inflamed eye bright red in

many vertebrates the scarer is

reinforced with plates of cartilage a

bone together forming a circular

structure called the sclerotic ring in

primitive fish this ring consists of

four plates but the number is lower in

many living Bray fin fishes and much

higher in lobe-finned fishes various

reptiles and birds the ring has

disappeared in many groups including

living amphibians some reptiles and fish

and all mammals the eyes of all

non-human primates a dark with small

barely visible sclera histology the

collagen of the sclera is continuous

with the cornea from outer to inner most

the four layers of the scarer are a piss

clearer

stroma lamina fusca endothelium the

scarer is Oh peg due to the irregularity

of the type one collagen fibers as

opposed to the near uniformed thickness

and parallel arrangement of the corneal

collagen

moreover the cornea bears more

mucopolysaccharides

to embed the fibrous the cornea unlike

the sclera has five layers the middle

thickest layer is also called the stroma

the sclera like the cornea contains a

basal endothelium above which there is

the lamina fusca containing a high count

of pigment cells sometimes very small

grey blue spots can appear on the sclera

a harmless condition called scarole

melanocyte ptosis function human eyes

are somewhat distinctive in the animal

kingdom in that the sclera is very

plainly visible whenever the eye is open

this is not just due to the white color

of the human sclera which many other

species share but also to the fact that

the human iris is relatively small and

comprises a significantly smaller

portion of the exposed eye surface

compared to other animals it is

theorized that this adaptation evolved

because of our social nature as the

I became a useful communication tool in

addition to a sensory organ it is

believed that the conspicuous carer of

the human eye makes it easier for one

individual to infer where another

individual is looking increasing the

efficacy of this particular form of

nonverbal communication animal

researchers have also found that in the

course of the domestic.