Eyes Flashcards
Ciliary Body
-Smooth muscle attached to lens
Ciliary Zonule
-suspensory ligament that attaches the lens to the ciliary body in the anterior eye
Cornea
- Transparent, central anterior portion
- Allows for light to pass through
- Repairs itself easily
- The only human tissue that can be transplanted without fear of rejection
Iris
-regulates amount of light entering eye
Pupil
-rounded opening in the iris
Aqueous Humor
- Watery fluid found between lens and cornea
- Similar to blood plasma
- Helps maintain intraocular pressure
- Provides nutrients for the lens and cornea
- Reabsorbed into venous blood through the scleral venous sinus, or canal of Schlemm
Lens
- Biconvex crystal-like structure
- Held in place by a suspensory ligament attached to the ciliary body
Canal of Schlemm
-Aqueous humor fluid is reabsorbed into venous blood
Vitreous Humor
- Gel-like substance posterior to the lens
- Prevents the eye from collapsing
- Helps maintain intraocular pressure
Sclera
- White connective tissue layer
- Seen anteriorly as the “white of the eye”
Choroid
- blood-rich nutritive layer in the posterior of the eye
- Pigment prevents light from scattering
Retina
- Outer pigmented layer
- Inner neural layer
- Contains receptor cells (photoreceptors)
- Rods- Images - Cones-Colors
Fovea Centralis
-area of the retina with only cones
Optic Nerve
-Receives impulses for interpreting sight
Central Artery and Vein of the Retina
-Vascularize the eye
Optic Disc (Blind Spot)
- where the optic nerve leaves the eyeball
- Cannot see images focused on the optic disc
Accessory Structures of the Eye
- Eyelids and Eyelashes
- Conjunctiva
- Lacrimal Apparatus
- Extrinsic Eye Muscles
List of Extrinsic Eye Muscles
- Lateral Rectus: Moves eye laterally
- Medial Rectus: Moves eye medially
- Superior Rectus: Elevates eye and turns it medially
- Inferior Rectus: Depresses eye and turns it medially
- Inferior Oblique: Elevates eye and turns it laterally
- Superior Oblique: Depresses eye and turns it laterally
Eyelids and Eyelashes
- Tarsal glands lubricate the eye
- Ciliary glands are located between the eyelashes
Conjunctiva
- Membrane that lines the eyelids
- Connects to the surface of the eye
- Secretes mucus to lubricate the eye
Lacrimal Apparatus
- Lacrimal gland—produces lacrimal fluid
- Lacrimal canals—drain lacrimal fluid from eyes
- Lacrimal sac—provides passage of lacrimal fluid towards nasal cavity
- Nasolacrimal duct—empties lacrimal fluid into the nasal cavity
Properties of Lacrimal Fluid
- Dilute salt solution (tears)
- Contains antibodies and lysozyme (avoid bacterial infections)
Functions of the Lacrimal Apparatus
- Protects, moistens, and lubricates the eye
- Empties into the nasal cavity
Cones
- Allow for detailed color vision
- Densest in the center of the retina
- Cone Sensitivity:
- Three types of cones
- Different cones are sensitive to different wavelengths
- Red, Green, Yellow
- Color blindness is the result of the lack of one cone type
Rods
- Most are found towards the edges of the retina
- Allow dim light vision and peripheral vision
- All perception is in gray tones
Night Blindness
-inhibited rod function that hinders the ability to see at night
Glaucoma
-can cause blindness due to increasing pressure within the eye
Hemianopia
- loss of the same side of the visual field of both eyes
- results from damage to the visual cortex on one side only
Cataracts
- when lens becomes hard and opaque
- our vision becomes hazy and distorted
Color Blindness
- genetic conditions that result in the inability to see certain colors
- Due to the lack of one type of cone (partial color blindness)
Emmetropia
-eye focuses images correctly on the retina (normal vision)
Astigmatism
- Images are blurry
- Results from light focusing as lines, not points, on the retina due to
- unequal curvatures of the cornea or lens
Hyperopia (Farsighted)
- Near objects are blurry while distant objects are clear
- Distant objects are focused behind the retina
- Results from an eyeball that is too short or from a “lazy lens”
Myopia (Nearsighted)
- Distant objects appear blurry
- Light from those objects fails to reach the retina and are focused in front of it
- Results from an eyeball that is too long
Pathway of Light Through the Eye
- Light must be focused to a point on the retina for optimal vision
- The eye is set for distance vision (over 20 feet away)
- Accommodation—the lens must change shape to focus on closer objects (less than 20 feet away)
- Image formed on the retina is a real image
- Real images are
- Reversed from left to right
- Upside down
- Smaller than the object
- Real images are
Ophthalmoscope
- Instrument used to illuminate the interior of the eyeball
- Can detect diabetes, arteriosclerosis, degeneration of the optic nerve and retina
Layers forming the wall of the eyeball
- Fibrous Layer: Outside layer for protection
- Vascular Layer: Middle Layer, blood transports oxygen and nutrients
- Sensory Layer: Inside Layer w/ nerves
