Overview Of The Eye Flashcards
What’s the technical word for structure
Anatomy
What’s the technical name for function
Physiology
What is an eye
The organ of sight allowing for imaging of the surroundings
How is a pinhole eye formed
Photosensory cells are invaginated forming a chamber and there is only a small hole that lets light into the photoreceptors cells
How is an image formed in a pinhole eye
Very narrow beams of light from each point of an object form an inverted image on the wall of the chamber
What is the image like that’s produced by a pin hole eye
Either extremely dim or extremely blurred
Where are camera type eye found
Invertebrates and vertebrates
How is an image formed in a camera type eye
A pupil that limits light and focused incoming light onto a photosensitive surface
In a camera type eye, what shape is the lens formed
Spherical
How is the lens in a camera type eye formed in terrestrial Arthropods
Thickening of the exoskeleton cuticle
What is the image like that’s produced by a camera type eye
Bright picture with high optical quality
Where’s a concave mirror found
Clam pecten and a few ostracod crustaceans
What kind of image does a concave mirror eye produce
Bright but reasonably hazy picture
Opsin
The protein part of the visual pigment
When did eyes first appear
About 600 million years ago
Crystallins
Structural proteins of lenses
Cambrian explosion
Appearance and diversification of multicellular organisms
Trilobites
Arthropods that became extinct about 200 million years ago
How are Arthropods characterised
By the possession of segmented body with appendages on each segment.
They have a dorsal heart and a central nervous system
What is the hard exoskeleton of Arthropods made of
Chitin, a polysaccharide which provide physical protection + resistance to desiccation
What happens when an Arthropods moults
It sheds its covering - exoskeleton
What eyes do Arthropods have
Compound eyes
What eyes do vertebrates have
Simple eyes
An evolutionary history
The emergence of our species and our eyes through geological time
A developmental history
Unfolding within the lifetime of an individual
Conjunctiva
A vascular membrane covering the sclera over the anterior segment of the eyeball and the adjacent surface of the eyelids
What are the 3 layers of the human eye
Outer
Middle
Inner
What does the outer layer of the human eye consist of and it’s purpose
Sclera
Cornea
= protection
What does the middle layer of the human eye consist of
Uvea (choroid ciliary body iris)
=vascular, pigmented
What does the inner layer of the human eye consist of
Retina
=photoreceptive
Dioptric appears consists of ……..
Cornea, lens, aqueous humour, vitreous humour
Corneosclera
Shape of the eyeball, protective
What are the appearance of
Sclera
Cornea
White
Transparent
What is the sclera
The opaque, fibrous, protective layer of the eye containing collagen + elastic fibres
What’s the sclera like in children
Thinner and shoes some of the underlying pigment, appearing slightly blue
What’s the sclera like in the old
Fatty deposits on the sclera can make it appear slightly yellow
What does the sclera form
The posterior five sixths of the connective tissue coat of the globe, offering resistance to the internal + external forces
What’s the thickness of the sclera
1mm at the posterior pole
To
0.33mm just behind the rectus muscle insertions
The corneas function :
Provides a protective coating to the eye
Transparent - provides a clear windscreen
Is an optical lens - carries out 2/3 of focusing of visible light on retina
What is the middle coat of the eye
Uvea = vascular coat
Describe middle coat of the eye/ uvea
Darkly pigmented (melanin) - absorption of light Blood supply to the structures in the eye- nutrition, gas exchange, waste removal Other functions specific for the iris + ciliary body - accommodation response enabling to focus on objects at different distances
What does the anterior uvea consist of
Iris
Ciliary body
What does the posterior u ea consist of
Choroid
Iris
A muscular diaphragm controlling the amount of light entering the eye
Ciliary body
A muscular structure involved in adjusting the refractive power of the lens
Choroid
Layer of pigmented vascular tissue between the retina + sclera
What is the inner coat of the eye
Retina
Describe the inner coat of the eye - retina
Complex layer of nerve cells connected to the rest of the brain by optic nerve which goes through a canal in the bony orbit - the optic foramen
Lies between the vitreous humour + the choroid
It can function (respond to light int.) over 11 orders of magnitude of light intensity
What makes up the retina
Rods and cones
Describe rods
Responsible for vision at low light (scotopic vision)
Do not mediate colour vision
Have a low spatial acuity
Describe cones
Active at higher light levels (photopic vision) Capable of colour vision 3 types of cones -short wavelength sensitive cones -Middle wavelength sensitive cones -long wavelength sensitive cones
What are short/middle/long wavelengths aka
S-cone
M-cone
L-cone
What are the functions of the retina
To detect + sample the inverted image projected upon it
To carry out initial neural integration + processing
To transmit the info in a precisely ordered pattern to the higher visual centres in the brain (the cortex)
Visual pathways
From the retina via optic nerve signal goes to the brain
Eye movements
Ocular muscles execute eye movements
Space between glove + orbit filled with orbital fat
Nerve supply needed to convey impulses to the eye, extra ocular muscles, ciliary muscle and iris
Sensory impulses carried from the eye (cornea+retina)
