Lab 11 Flashcards
Sclera
The white of the eye
It protects and shapes the eyeball and provides a sturdy anchoring site for the extrinsic eye muscles.
Cornea
The transparent layer anterior (in front of) of the sclera.
It allows light to enter the eye, and it helps bend/refract light rays so that they are focussed on the photo receptors in the retina.
Aqueous humor
Provides nutrients to the eye, and keeps the eye in a pressurized state.
Note: it is constantly being produced
Iris
The circular coloured portion of the eye which lies on top of the lens.
It regulates the amount of light that gets into the retina.
Contains:
Pupil - innermost central opening.
Inner circular muscle - will shrink the pupil in close and bright light.
Outer radial muscle - will expand the pupil in distant and dim light.
Lens
Flexible and able to change its shape to focus light rays for close and far vision into the retina.
Vitreous humor
Fluid which fills the inside of the eyeball.
It keeps the shape of the eye round, and absorbs shock.
Ciliary body
Attached to the back of the iris.
Contains:
Ciliary muscles - controls the shape of the lens.
Ciliary processes - contain capillaries that produce the aqueous humor
Choroid
A highly vascularized and pigmented tissue which is continuous with the ciliary body and wraps around the eye.
It will absorb excess light rays to prevent reflection and scattering of light in the eyeball
Retina
The innermost layer which lines the inner eyeball.
Contains photo receptors (rods and cones) which convert light into signals that are sent to bipolar cells, and then to ganglion cells where action potentials are generated.
Glaucoma
A condition caused by damage to the optic nerve resulting in vision loss
Cataract
A clouding of the lens due to changes in the tissue
Myopia
Causes individuals to see closer objects clearly, but distant objects are blurry. (Nearsightedness)
- eyeball is too long
- Lens is too curved
- focal point in front of the retina
Requires a concave lens for correction.
Hyperopia
Individuals can see distinct objects clearly, but close objects appear blurry. (Farsightedness)
- eyeball is too short
- lens is too flat
- focal point is behind the retina
Requires a convex lens for correction.
Astigmatism
When the cornea or lens has irregularities in the surface curvature.
Objects may be in focus in one axis, and blurred in another axis.
Optic disc
Area where the retina meets the optic nerve.
This area is also called the “blind spot” because it lacks photoreceptors.
Macula lutea
Contains a central portion called the fovea centralis which is the area in the eye that has the greatest visual sharpness.
This area contains only cones
What is the difference between rods and cones?
Rods - stimulated by dim light and produce shades of black, white, grey.
Cones - stimulated by bright light and produce colour vision
Accommodation
The ability of the eyes to focus on objects that are near or far.
What role do the suspensory ligaments and ciliary muscles play in accommodation?
These structures help change the shape of the lens to help focus on objects of varying distances.
Near point
The closest distance at which an object appears to be sharp and focus.
Near points can change over time:
(Average near point distance)
20 year olds = 10 cm
40 year olds = 20 cm
60 year olds = 20-80 cm
(This is why many people develop the need for reading classes)
Snellen test
Determines the smallest size of printed letters that could be clearly seen by an individual distance of 20 feet.
This thing:
F
C M
R G S
D Y X H
What are the 3 main regions of the ear, and what do they do?
External ear - collects sound waves and brings them into the middle ear.
Middle ear - transfers sound vibrations to the oval window.
Internal ear - contains receptors for hearing and equilibrium.
Auricle (or pinna)
The visible portion of the external ear which collects and directs sound waves into the ear
External auditory canal
Brings the sound waves picked up by the auricle to the tympanic membrane (eardrum)
It contains ceruminous glands to produce earwax which prevents dust/bacteria from damaging the ear.
