Anatomy – The Eye

light bending
refraction

ability to focus for close vision (under 20 ft)
accommodation

normal vision
emmetropia

inability to focus well on close objects; farsightedness
hyperopia

reflex constriction of pupils when they are exposed to bright light
photopupillary reflex

clouding of the lens, resulting in loss of sight
cataract

nearsightedness
myopia

blurred vision, resulting from unequal curvatures of the lens or cornea
astigmatism

condition of increasing pressure in the eye, resulting from blocked drainage of aqueous humor
glaucoma

medial movement of the eyes during focusing on close objects
convergence

reflex constriction of the pupils when viewing close objects
accommodation pupillary reflex

inability to see well in the dark; often a result of vitamin A deficiency
night blindness

extrinsic
Attached to the eyes are the ____ muscles that allow us to direct our eyes toward a moving object.

eyelids
The anterior aspect of each eye is protected by the ____, which have eyelashes projecting from their edges.

tarsal glands
Closely associated with the lashes are oil-secreting glands called ____ that help to lubricate the eyes.

ciliary zonule
ligament that attaches the lens to the ciliary body.

aqueous humor
Fluid in the anterior segment that provides nutrients to the lens & cornea.

sclera
The “white” of the eye.

optic disk
Area of retina that lacks photoreceptors.

tarsal glands
oil glands along the edges of the eyelids that lubricate the eye

ciliary body
Contains muscle that controls the shape of the lens.

choroid
Nutritive (vascular) layer of the eye.

canal of schlemm
Drains the aqueous humor of the eye.

Retina
Contains rods & cones; allows us to see color.

vitreous humor
Gel-like substance that helps to reinforce the eyeball.

iris & ciliary body
The anterior part of the choroid forms these two structures

fovea centralis
area of acute or discriminatory vision.

cornea
Most anterior part of the sclera-your “window on the world”

iris
Pigmented “diaphragm” of the eye.

I. Fibrous or Outer Tunic:
2. Vascular or Middle Tunic:
3. Nervous Tunic- Retina:
Three layers of the eye

The eye converts light energy into electrical nerve impulses(photoreceptors) that is in turn interpreted by the brain ( occipital lobe) as sight.
what is the function of the eye?

“photons”
Light is radiated in waves called _________

400- 700nm
Our receptors are stimulated by light wavelengths
in the visible spectrum…what area of the wavelength

Eyelashes. Eyebrows. Eyelids.
Lacrimal Ducts
what are the accessory structures of the eye?

anterior
posterior
what are the Two Cavities of the eye?

1. Anterior- filled with aqueous humor that is
produced by the choroid plexuses and drained
by the Canal ofSclemm: in front of lens.
2. Posterior- filled with a jelly-like vitreous humor
that is formed in the embryonic stage; behind
lens.
describe the two cavities of the eye…

1. Extrisinsic- outside, voluntary, move
the eyeball
2. Intrinsic-inside,involuntary .

Iris=opens and closes pupil regulating size

Ciliary muscles= controls shape of
lens to accommodate for near/far
focusing

describe the eye muscles

I. Photoreceptorlaver- generatesaction
potential; made of rods and cones
2. Bipolar laver- transmits impulse
3. Ganglion cells- relays message to optic
nerve and then to occipital lobe
Three layers of the retina

Detect photons
What do the rods and cones do?

RODS: . Found around periphery ( 120 million) . Light and dark discrimination. Dim light vision Shape and movement
describe the rods

cones
neurons in the retina that are responsible for color vision

Concentrated in small depression called the
“fovea” in macula utea at center of retina . Bright light vision . Color vision . Sharpness of image
give more detail about cones

1. Cornea and lens must refract light to retina
2. Accomodation of the lens- to adjust for near
and far focus ( ciliary muscles & suspensory
ligaments)
Near- thick lens ( muscle contracts)
Far- thin lens ( muscle relaxes)
3. Constriction of Pupil- light control
4. Convergence of two eyeballs to focus on an
object by extrinsic muscles
Before light can reach the rods and cones of the
retina, four things must occur:

I. Light enters the pupil
2. Image formed on the retina
3. Rods and Cones get excited and generate action potential
Rhodopsin undergoes structural change
This triggers a chain of enzymatic reactions
Enzymatic reactions cause changes in the permeability of the neuron membrane causing it to go from polarized to depolarized
4. Imbalance of the ions produces a “signal” in the bipolar
cells
5. Excitatory signal transmits to ganglion cells
6. Ganglion cells transmit impulse through optic nerves
7. Impulses meet at optic chiasma
8. Impulse sent to occipital lobe for interpretation
Physiology of sight

cornea, aqueous humor, lens, vitreous humor
refractory media of the eye

optic nerve
optic chiasma
optic tract
optic radiation
Name in sequence the neural elements of the visual pathway, beginning with the retina and ending with the optic cortex.

Retina–________–________–__________

Synapsein thalamus –__________–Optic cortex

Comea- transparent (fibrous tissue)
Sclera- White portion ( dense fibrous tissue)
Canal ofSchlemm- drainage of humor
found in the outer fibrous tunic layer of the eye

Choroid- brown pigment
Ciliary body- muscle that controls lens shape; aqueous humor
Iris
Pupil
found in the Vascular or Middle Tunic

inner layer of the eye containing the retina functioning in image formation
found in the Inner or Nervous Tunic

inner tunic
the retina is the ___ ___ of the eye

detached retina
separation of the retina from the choroid layer of the eye

sharpness or clearness of vision in one or both eyes
visual acuity

Orbit
Is a cone-shaped cavity in the front of the skull that contains the eyeball.

photopigment
A chemical in the photoreceptors that changes its form in response to light, producing an electrical change that signals to the nervous system that light is present.

opsin
A protein component of photopigment

rhodopsin
the light-sensitive pigment of the cells in the retina; it contains vitamin A.

C) lateral rectus
Which of the following extrinsic eye muscles is responsible for rotating the eye laterally?
A) inferior rectus
B) inferior oblique
C) lateral rectus
D) medial rectus
E) superior rectus

C) retina
Which of the following is part of the inner tunic of the eye?
A) lateral rectus muscle
B) iris
C) retina
D) sclera
E) conjunctiva

E) all of the above
The fibrous tunic of the eye
A) consists of the sclera and the cornea.
B) provides mechanical support and some protection for the eye.
C) serves as a point of attachment for extrinsic eye muscles.
D) A and C only
E) all of the above

D) A and B only
The lacrimal glands
A) are located in pockets in the frontal bones.
B) produce most of the volume of tears.
C) produce a slightly acidic secretion that contains lysozyme.
D) A and B only
E) all of the above

B) cornea.
The transparent portion of the eye is the
A) conjunctiva.
B) cornea.
C) iris.
D) pupil.
E) canthus.

C) iris.
The pigmented portion of the eye is the
A) conjunctiva.
B) cornea.
C) iris.
D) pupil.
E) canthus.

A) anterior chamber.
The space between the iris and the cornea is the
A) anterior chamber.
B) posterior chamber.
C) pupil.
D) aqueous humor.
E) vitreous body.

C) changing shape.
The lens focuses light on the photoreceptor cells by
A) moving up and down.
B) moving in and out.
C) changing shape.
D) opening and closing.
E) dilating and constricting.

C) ciliary muscles.
The shape of the lens is controlled by the
A) pupillary constrictor muscles.
B) pupillary dilator muscles.
C) ciliary muscles.
D) suspensory ligaments.
E) aqueous body.

B) control the shape of the lens.
The ciliary muscle helps to
A) control the amount of light reaching the retina.
B) control the shape of the lens.
C) control the production of aqueous humor.
D) move the eyeball.
E) both A and B

A) cause contraction of the pupillary constrictor muscles
A sudden flash of bright light would
A) cause contraction of the pupillary constrictor muscles.
B) cause contraction of the pupillary dilator muscles.
C) cause relaxation of the ciliary body.
D) cause relaxation of the ciliary ligaments.
E) increase the size of the iris.

A) rounded.
When viewing an object close to you, your lens should be more
A) rounded.
B) flattened.
C) convex.
D) lateral.
E) medial.

B) filled with aqueous humor.
The anterior cavity is
A) hollow.
B) filled with aqueous humor.
C) filled by the vitreous body.
D) filled with perilymph.
E) filled with endolymph.

E) clarity of vision.
Visual acuity is also known as
A) nearsightedness.
B) farsightedness.
C) myopia.
D) astigmatism.
E) clarity of vision.

A) a cataract.
Loss of lens transparency is referred to as
A) a cataract.
B) glaucoma.
C) myopia.
D) accommodation.
E) corneal scarring.

D) emmetropia.
Normal eye focusing is termed
A) hyperopia.
B) myopia.
C) presbyopia.
D) emmetropia.
E) refraction.

C) the optic nerve attaches to the retina.
A blind spot in the retina occurs where
A) the fovea is located.
B) ganglion cells synapse with bipolar cells.
C) the optic nerve attaches to the retina.
D) rod cells are clustered to form the macula.
E) amacrine cells are located.

B) ciliary muscles relax.
The lens of the eye thickens when the
A) conjunctiva contracts.
B) ciliary muscles relax.
C) ciliary muscles contract.
D) ciliary processes contract.
E) suspensory ligaments pull on the lens.

C) lens.
Treatment of a cataract usually involves removal of the
A) cornea.
B) iris.
C) lens.
D) sclera.
E) vitreous humor.

A) vitamin A.
Night blindness can be treated by administering
A) vitamin A.
B) vitamin D.
C) vitamin E.
D) vitamin K.
E) vitamin C.

B) red, blue, and green.
There are three different types of cones, each one sensitive to a different color wavelength of light. These cones are designated
A) red, yellow, and blue.
B) red, blue, and green.
C) red, green, and yellow.
D) yellow, green, and blue.
E) red, yellow, and indigo.

D) white.
When all three cone populations are stimulated, one sees
A) red.
B) blue.
C) green.
D) white.
E) black.

A) rods.
Rhodopsin is found in
A) rods.
B) cones.
C) visual pigments.
D) sodium pumps.
E) neurotransmitters.

choroid coat
posterior five-sixths of middle (vascular) tunic

sclera
white part of outer (fibrous) tunic

cornea
transparent anterior portion of outer tunic

conjuctiva
inner lining of eyelid

lacrimal glands
secretes tears

vitreous humor
fills posterior cavity of eye

optic disk
area where optic nerve meets eye

iris
smooth muscle that controls light entering the eye

aqueous humor
fills anterior and posterior chambers of the anterior cavity of the eye

retina
contains visual receptors called rods and cones

suspensory ligament
connects lens to the ciliary body

ciliary muscles
causes lens to change shape

cornea…aqueous humor..pupil of iris…lens…vitreous humor…retina
list the structures and fluids through which light passes as it travels from the cornea to the retina

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