exam 4 - vision

layers of the eye (tunics)

fibrous tunic (outer layer)

vascular tunic (middle layer)

retina (inner layer)

fibrous tunics sub layers

sclera and cornea

slcera

fibrous tunic layer

The white, tough part of the eye;

it provides protection and maintains the shape of the eye.

cornea

The clear, dome-shaped front part;

it focuses light entering the eye

provides a protective barrier

vascular tunic layers

choroid layer

cilary body

iris

choroid

vascular tunic layer

A layer with blood vessels;

supplies oxygen and nutrients to eye tissues

ciliary body

Contains muscles that control the shape of the lens

produces aqueous humor

iris

The colored part of the eye;

controls the size of the pupil

regulate the amount of light entering

what does retina contain

contains photoreceptors (rods and cones) that detect light and send visual information to the brain via optic nerve

2 main cavities of eye filled with fluid

aqueous and vitreous humors.

anterior cavity

front of lens

aqueous humor

A clear, watery fluid produced by the ciliary body;

it nourishes the cornea and lens

helps maintain intraocular pressure

aqueous humor is divided into 2 chambers

anterior chamber

posterior chamber.

anterior chamber

Between the cornea and the iris

posterior chamber

Between the iris and the lens.

vitreous humor

A clear, gel-like substance;

it helps maintain the eye’s shape

keeps the retina in place by pressing it against the choroid.

lens structure

A transparent, flexible structure located directly behind the iris.

lens function

It focuses light on the retina by changing shape, a process known as
accommodation.

how does ciliary body aid in lens accomodation

• Thicker for nearby objects.
• Thinner for distant objects.

conjunctiva

A thin, transparent membrane covering the white part of the eye (sclera) and inner surface of the eyelids.

It provides lubrication and protection

steps in order of tear flow/ lacrimal flow

tear production

spreading across eye

tear drainage

into nasal cavity

main flow of tears

Lacrimal gland → spreads across eye → puncta → canaliculi → lacrimal sac → nasolacrimal duct → nasal cavity

tear production process

Tears are produced by the lacrimal gland, located above the outer
corner of each eye.

tears Spreading Across the Eye process

Each time you blink, tears spread across the surface of your
eye, keeping it moist, washing away dust, and protecting against infection

tear drainage process

Tears then drain into small openings (called puncta/punctum) located in the inner corner of each eyelid.

tears into Nasal Cavity process

From the puncta, tears travel through small canals (called
canaliculi) to a sac in the inner corner of the eye (the lacrimal sac). They then drain down through the nasolacrimal duct into the nasal cavity.

retina note

The retina has a somewhat

counterintuitive structure — it is "inverted", meaning that light must pass through several layers
of neural cells before reaching the photoreceptors that actually detect it

layers of light pass through

front to back

1.Ganglion cell layer
2. Bipolar cell layer
3. Photoreceptor layer (rods and cones – the deepest layer)

thalamus

a relay center in the brain that helps direct sensory
information to the appropriate brain areas

rods

Primarily responsible for vision in low light (night vision).
• Detect black, white, and shades of gray – they do not perceive color.
• Excellent at detecting motion in dim lighting.
• High sensitivity to light, allowing vision in dimly lit environments.
• Poor at detecting fine detail because they are mostly used in peripheral vision

cones

Responsible for color vision and fine detail.
• Work best in bright light.
• Allow us to see in sharp focus and distinguish colors (red, green, and blue).
• Low sensitivity to light, meaning they do not function well in low light.
• Essential for activities that require detailed vision, like reading and identifying colors

who are the first to respond to light

photoreceptors are the first to respond to light, initiating the visual
process

optic nerve (cranial nerve II)

transmits the visual information out of the eye.