Internal Eye Structure Flashcards
composed of three separate coats or layers. The external layer consists of the sclera and cornea.
Eyeball
is a dense, protective, white covering that physically supports the internal structures of the eye
Sclera
(the “window of the eye”).
Permits the entrance of light, which passes through the lens to the retina.
It is well supplied with nerve endings, making it responsive to pain and touch.
Cornea
stimulates a blink in both eyes.
is supported by the trigeminal nerve, which carries the afferent sensation into the brain, and the facial nerve, which carries the efferent message that stimulates the blink.
Corneal reflex
Anterior portion in the middle layer.
Is a circular disc of muscle containing pigments that determine eye color.
Iris
Central aperture of the iris.
Controls the amount of light entering the eye.
Pupil
Is a biconvex, transparent, avascular, encapsulated structure located immediately posterior to the iris.
Functions to refract (bend) light rays onto the retina.
Bulges to focus on close objects and flattens to focus on far objects.
Lens
Posterior portion in the middle layer.
Ciliary body consists of muscle tissue that controls the thickness of the lens, which must be adapted to focus on objects near and far away.
Contains the vascularity necessary to provide nourishment to the inner aspect of the eye and prevents light from reflecting internally.
Choroid
Innermost layer and extends only to the ciliary body anteriorly.
It receives visual stimuli and sends it to the brain.
Consists of numerous layers of nerve cells, including the cells commonly called
Retina
Rods and cones
These specialized nerve cells are often referred to as “____________” because they are responsive to light.
Photoreceptors
are highly sensitive to light, regulate black-and-white vision, and function in dim light.
Rods
function in bright light and are sensitive to color
Cones
Is a cream-colored, circular area located on the retina toward the medial or nasal side of the eye.
It is where the optic nerve enters the eyeball.
Can be seen with the use of an ophthalmoscope and is normally round or oval in shape, with distinct margins.
A smaller circular area that appears slightly depressed is referred to as the physiologic cup. This area is approximately one-third the size of the entire optic disc and appears somewhat lighter/whiter than the disc borders.
Optic disc
Can be readily viewed with the aid of an ophthalmoscope.
Four sets of arterioles and venules travel through the optic disc, bifurcate, and extend to the periphery of the fundus.
Venules are dark red and grow progressively narrower as they extend out to the peripheral areas.
Arterioles carry oxygenated blood and appear brighter red and narrower than the veins.
Retinal vessels
varies in color, depending on skin color.
Fundus
known as the fovea centralis is located adjacent to the optic disc in the temporal section of the fundus.
Retinal depression
appears darker than the rest of the fundus.
Macula
