Vision Anatomy Part 2 (2) Flashcards
hat is the ciliary body?
Anteriorly, the choroid becomes the ciliary body, a thickened ring of tissue that encircles the lens
(trampoline) and has 3 parts
What are the 3 parts of the ciliary body?
Ciliary muscles, ciliary processes and ciliary zonules
What is the ciliary muscle?
Make up most of ciliary body
Smooth muscle bundles that control lens shape
What do the ciliary processes do?
Secrete the fluid that fills the cavity of the anterior segment of the eyeball
What are the ciliary zonules?
They extend from the ciliary processes to the lens
Halo of fine fibers that encircle the circumference of the lens and helps hold it in upright position
What is the iris?
Colored part of eye
Most anterior portion of the vascular layers
Lies between cornea and lens, and is continuous with the ciliary body posteriorly
What does the pupil do?
Allows light to enter the eye
What 2 smooth muscle layers make up the iris?
Sphincter pupillae and dilator papillae
The sphincter pupillae is…
Parasympathetic
The dialtor pupillae is…
Sympathetic
Our pupils often dilate when we see something that…
appeals us
when we feel fear
during problem solving
Our pupils often constrict when we are…
Bored
viewing something that is unpleasant
What is the sensory tunic (retina)?
The innermost layer of the eyeball (delicate)
What are the 2 layers the sensory tunic (retina) made up of?
Pigmented and neural (not fused together)
Which layer of the retina plays a direct role in vision?
Neural layer
What does the pigmented layer of the retina do?
Absorbs excess light and prevents it from scattering
What 3 cells make up the neural layer of the retina?
Photoreceptors, bipolar cells and ganglion cells
What two cells make up photoreceptors?
Rods and cones
What are rod cells?
They are our dim-light and peripheral vision receptors
There are __________ rod cells and far more _________ to light than cones
numerous, sensitive
How many rod cells attach to a bipolar cell?
Many
How many cone cells attach to a bipolar cell?
1
What do cone cells do?
They are our vision receptors for bright light and provide high-resolution color vision
All photoreceptors synapse with…
bipolar cells
All bipolar cells synapse with…
ganglion cells
Which cells send the action potential?
Ganglion
What is the fundus?
Posterior wall of the eye
What is the optic disc?
Where the nerve exits the eye
Is a weak spot in the fundus (posterior wall) because it is not reinforced by the sclera
The blind spot
What is the macula lutea?
Lateral to the blind spot in the eye
Allows light to pass almost directly to the photoreceptors, greatly enhancing the ability to resolve detail
What is the fovea?
The pit in the center of the macula lutea
The fovea contains only…
cones
The macula lutea contains mostly _____ and from the edge of the macula toward the retina periphery, ____ ________ declines gradually
cones
cone density
(move away from macula lutea means more rods, less cones)
The lens is divided into what 2 segments?
Anterior segment and posterior segment
The posterior segment is filled with what fluid?
Vitreous humor
The vitreous humor transmits…
light
The vitreous humor supports…
the posterior surface of the lens and holds the neural layer of the retina firmly against the pigmented layer
The vitreous humor contributes to…
intraocular pressure, helping counteract the pulling force of the extrinsic eye muscles
What are the 2 anterior segment divisions?
Anterior chamber and posterior chamber
Where is the anterior chamber?
Between the cornea and the iris
Where is the posterior chamber?
Between the iris and the lens
What is the entire anterior segment filled with?
Aqueous humor
What is aqueous humor?
A clear fluid similar in composition to blood plasma
Does vitreous humor form and drain continuously?
No
Does aqueous humor form and drain continuously?
Yes
Where does aqueous humor drain from?
Scleral venous sinus
What does aqueous humor do?
Supplies nutrients and oxygen to the lens and cornea
What is a cataract?
A clouding of the lens that causes the world to appear distorted (seeing through a foggy glass)
How are cataracts formed?
Age-related hardening and thickening of the lens
Heavy smoking
Frequent exposure to sunlight
