Photoreceptors = _________ ________ used to detect ____, _______, and movement
visual receptors, light, color
The lacrimal fluid prevents infection because it contains an antibacterial enzyme called ___________________
lysozyme
Relationship between sclera, cornea, and conjunctiva?
What is each external accessory structure?
Sclera= white portion of eyeball; covered by conjunctiva
Cornea= clear layer; part of fibrous tunic of eye; NOT covered by conjunctiva
Conjunctiva= possesses many blood vessels, nerve endings, and goblet cells which lubricate and moisten the eye
What is the lacrimal caruncle?
fleshy, red tissue where inferior and superior eyelids meet medially
contains sebaceous glands and ciliary glands
Purpose of the following external accessory structures?
Eyebrows
Eyelashes
Eyebrows- prevent sweat from dripping into open eyes
Eyelashes- prevent large objects from coming into contact with eye
Describe eyelids.
What glands they contain, what they're separated by, where they are united both laterally and medially?
Eyelids contain tarsal glands
Separated by central palpebral fissure
United at medial and lateral palpebral commissures
What are tarsal glands and where are they located?
located between cornea and eyebrows, near palpebral conjunctiva
secrete meibum to keep eyes moist
Describe the lacrimal apparatus and it's order of events.
1) Lacrimal fluid (tears) are produced in the lacrimal gland
2) Tears are dispersed across eye surface when we blink.
3) Tears enter the lacrimal puncta which help drain tears into the lacrimal canaliculi
4) From lacrimal canaliculi, tears collect in the
Which bones make up the bony orbit?
1) Frontal bone
2) Sphenoid bone
3) Zygomatic bone
4) Maxilla bone
5) Palatine bone
6) Lacrimal bone
7) Ethmoid bone
Which CN innervate which extrinsic eye muscles?
SO(4)LR(6)R(3)
Superior oblique- CN IV (Trochlear)
Lateral rectus- CN VI (Abducens)
Inferior oblique, inferior rectus, medial rectus, superior rectus, levator palpebrae- CN III (Occulomotor)
What are the three layers of the eye from external to internal?
1) Fibrous tunic
2) Vascular tunic
3) Neural tunic (Retina)
Purpose of orbital fat?
cushions posterior and lateral eye; provides support and protection
Describe the cavities of the eye including where they are located and what they contain.
Contains two cavities:
1) Posterior cavity (behind the lens to end of retina): contains permanent, static vitreous humor
2) Anterior cavity (in front of lens to cornea): contains circulating aqueous humor
- further divided into anterior and posterior cham
What is the name for the structure/ "edge of the retina" that separates the retina from the ciliary body?
ora serrata
Fibrous tunic composed of which two eye structures
AND
name of the area where the two structures meet?
sclera and cornea
limbus= corneal scleral junction
3 Purposes of the Sclera?
1) Protects structure of eye
2) Protects fluids inside the eye
3) Serves as an attachment site for extrinsic eye muscles
Purpose of the Cornea?
to refract light onto the lens (located behind pupil) which then refracts light and focuses it onto the retina
What are the 2 layers of the cornea? Describe where each gets its nutrients from.
Entire cornea is avascular SO
External epithelium- receives nutrients and O2 from lacrimal gland fluid
Internal epithelium- receives nutrients and gases from fluid in anterior chamber
What are the three regions of the vascular tunic of the eye?
Choroid, Ciliary body, Iris
Describe choroid:
a) what is it,
b) where is it located,
c) what kinds of vessels/cells live here?
a) region of the vascular tunic
b) located posterior to ciliary body
c) here, capillaries help nourish retina & melanocytes produce melanin to absorb extraneous light
Describe ciliary body:
a) what is it,
b) what are it's accessory structures and what do they do
c) where is it located
a) region of the vascular tunic
b) ciliary body contains
1. ciliary muscles (allow ciliary body to move away or towards the lens --> suspensory ligaments --> lens shape changes)
2. ciliary processes (contain capillaries that secrete aqueous humor to fill
Describe iris:
a) what is it,
b) what does it contain
c) what does it cause a division of
a) colored portion of the eye; most anterior region of the vascular tunic
b) contains two layers of pigment-forming cells and two groups of smooth muscle fibers (because it's surrounding pupil that needs to constrict based on how much light needs to be al
What gives color to the iris?
melanin + hemoglobin
What is the order of the structures of the vascular tunic from anterior --> posterior?
Iris --> Ciliary body --> Choroid
Describe difference between sphincter pupillae muscle and dilator pupillae muscles.
Sphincter pupillae m.- resembles concentric circles, contracts when stimulated by high light level --> constricts pupils, controlled by PSNS
Dilator pupillae m.- resembles a radial pattern, contracts when stimulated by low light level --> dilates pupils,
Name the two regions of the retina.
1) Pigmented Layer
2) Neural Layer (Internal to Pigmented Layer)
Describe the pigmented layer of the retina.
internally attached to choroid;
provides vitamin A for photoreceptors;
if it wasn't for this layer, light would bounce back/scatter to outside the retina instead of being absorbed
Describe the neural layer of the retina.
internal to pigmented layer of retina;
receives light and converts it into nerve signals;
composed of 3 sub layers: (superficial to deep) photoreceptors, bipolar cells, ganglionic cells
*horizontal cells ("horizontally") separate the photoreceptor cells f
Describe the ora serrata.
Boundary between photosensitive and nonphotosensitive parts of the retina (nonphotosensitive part is anterior-- covers ciliary body and posterior side of iris)
Describe what happens with the neural layer of the retina as light enters in this region.
Light passes through ganglion --> amacrine --> bipolar --> horizontal --> photoreceptor cells
Once light hits the photoreceptor cells, they become activated and a nerve signal is sent in the opposite direction of the light.
Photoreceptors create a graded
Axons of ganglion cells gather together to form a "_________" at the _______ _______ which becomes the ______ _______.
carpet,
optic disc,
optic nerve
What is the optic disc?
a blind spot lacking photoreceptors
Horizontal and amacrine cells _________ ___________ to the retinal layers.
provide assistance
Only _______________ and ______________ cells can produce AP, other cells produce graded potential.
amacrine, ganglion (of retina)
Name 3 components (NOT REGIONS) of the retina.
1) Optic disc
2) Macula lutea
3) Peripheral retina
Describe the optic disc.
1) component of retina
2) contains no photoreceptors = blind spot
3) where ganglion axons exit to form optic nerve to take signal to brain
Describe the macula lutea.
1) component of retina
2) lateral to optic disc
3) contains fovea centralis
Describe the fovea centralis.
1) central pit of the macula lutea
2) highest [ ] of cones exist here; very few rods
3) area of sharpest vision of retina
Describe the peripheral retina.
1) component of the retina
2) contains mainly rods
3) functions most effectively in low light
4) remainder of retina that isn't macula lutea or optic disc
What is the purpose of the lens and what types of cell does it possess?
lens changes shape to FOCUS and REFRACT light onto the retina
cells of the lens are filled with crystallin protein
Which structures perform refraction and which structures perform focusing of light?
Refraction structures = cornea, lens
Focusing structures = ciliary muscles, lens
How does the lens change shape in far vision (20 or more feet away)?
When ciliary m. are RELAXED, ciliary body moves away, pulling suspensory ligaments, causing tension on suspensory ligaments, causing lens to become flat
There is a ______ on the outer lens where suspensory ligaments attach on to connect the _________ _______ to the lens.
capsule, ciliary body
How does the lens change shape in near vision (closer than 20 feet) (during ACCOMMODATION)?
When ciliary m. are CONTRACTED, ciliary body moves towards lens, releasing tension from suspensory ligaments, causing lens to become more spherical
Describe production, circulation, and drainage of aqueous humor.
Purpose?
gelatinous or watery?
Blood capillaries in ciliary processes produce aqueous humor.
Aqueous humor flows from posterior chamber, through pupil to anterior cavity, and remainder is reabsorbed by the sclera venous sinus.
purpose= nourish and oxygenate lens and inner cornea
watery
Where does vitreous humor come from and what space does it occupy?
Purpose?
gelatinous or watery?
permanent vitreous humor produced originally in embryonic development
vitreous humor fills up entire posterior cavity
purpose= to put pressure on retina to keep it against the back of the eye
gelatinous
What is the scleral venous sinus?
opening near the limbus where aqueous humor is reabsorbed into
How does glaucoma occur?
When there isn't enough drainage of aqueous humor by the scleral venous sinus --> accumulation and tension of aqueous humor
Difference between Emmetropia, Hypermetropia, Myopia- Eyeball Shape?
Emmetropia- normal shape
Hypermetropia- short eyeball
Myopia- long eyeball
Difference between Emmetropia, Hyperopia, Myopia- Light Rays on Retina
Emmetropia- parallel light rays focused on retina
Hyperopia- only convergent rays from distant points brought to focus = FAR SIGHTED
Myopia- only nearby rays close to eye brought to focus = NEAR SIGHTED
Difference between Emmetropia, Hyperopia, Myopia- Corrected With
Emmetropia- normal vision, no correction needed
Hyperopia- farsightedness only, eyes are too short, convex lens needed for correction
Myopia- nearsightedness only, eyes are too long, concave lens needed for correction
What is presbyopia? Astigmatism?
age-related change in vision;
unequal focusing + unequal curvatures in one or more refractive surfaces
Clinical View: Detached Retina: what is this?
occurs when outer pigmented and inner neural layers separate;
increased risk if diabetics and nearsighted individuals;
results in nutrient deprivation;
symptoms= "floaters"/"curtain" in affected eye, flashes of light, decreased vision
Clinical View: Macular Degeneration: what is this?
physical deterioration of macula lutea;
leading cause of blindness in developed countries;
loss of visual acuity in center of visual field;
diminished color perception and "floaters
Rods vs. Cones:
#?
Respond to?
Color?
Rods: more numerous, respond to dim light/night vision, no
Cones: less numerous, respond to bright light, yes
Rods vs. Cones:
Primary Location?
Sharpness of Vision?
Other?
Rods: peripheral retina, no
Cones: fovea centralis, yes, subdivided into blue, green, and red (NOT YELLOW) cones
Rods vs. Cones:
Relationship with Bipolar and Ganglion Cells?
Result ^ = ?
Rods: any rods converge onto fewer bipolar cells which converge onto few ganglion cells; result = sensitivity to dim light but blurry image
Cones: have one-to-one relationship with bipolar and ganglion cells; result = sharp image but only in bright light
What is the difference between visual field and visual acuity and resolving power?
Visual field= entire area observed when eye focused on single point
Visual acuity= clearness of vision
Resolving power= ability to form separate/distinct images of close objects
Describe the concept of refraction and the focusing of light.
Light rays are refracted when they pass between media of different densities
Is the cornea more important than the lens? Explain why or why not.
Cornea is not more important than the lens. However, refraction occurs first here and is the greatest when rays pass into the cornea.
Then, refraction at a smaller resolving power occurs at lens
Photoreceptors extend into the ___________ ___________ of retina and are composed of hundreds of _________ ___________ sacs.
They are _________ replaced.
pigmented layer,
flattened membraneous,
continously
Opsin is a ___________ found in __________ and each photoreceptor has ____________ ospin type(s).
protein, photopigments,
only one
Photopigments contain retinal which is a ____________ _________ formed from ________ _____.
light-absorbing, molecule,
Vitamin A
What is the difference between rhodopsin and photopsin?
Rhodopsin= found in rods and involved in the transduction of DIM light
Photopsin= specific opsin associated with one of the three colors of cones
Color blindness is a ______________ ____________ condition more common in males. It indicates the absence of deficit in one type of _______ ________.
_________ and ________ are most commonly affected.
Are there others that are also affected?
X-linked recessive,
cone cell,
Red, green
Other colors are also affected but not as much as red and green
Define phototransduction
process by which photoreceptors are activated
Optic nerve formed from __________ __________ axons; they project from each eye, converge at the _________ _______.
_________ axons cross to opposite side of the brain.
_________ axons remain on the same side of the brain.
(*same concept as the diagram fr
Converging ganglionic,
optic chiasm
Medial, lateral
Optic tracts extend ___________ from the optic chiasm and are composites of _________ from _________ eye(s).
laterally, axons, both
Pathway of Vision:
1)Light rays enter eye --> cornea refracts rays to lens
2) Pupil...
3) Lens...
4) Rays are focused to an inverted image on a specific part of the retina
5) Lens...
6) Photoreceptors hyperpolarize in presence of light and stop inhibiting
2) Pupil constricts or dilates to regulate amount of light.
3) Light rays are further refracted by the lens
4) Rays focus an inverted image on specific part of retina
5) Lens flattens to view faraway objects
7) Bipolar cells release neurotransmitter --> N
What is the iris known as when compared with the analogy of a camera?
the diaphragm as it controls pupil size
What is the palpebral conjunctiva?
The part of the conjunctiva, a clear membrane, that coats the inside of the eyelids.