PART 1: THE EYE AND VISION Flashcards
large, complex sensory organs (eyes and ears) or localized clusters of receptors (taste buds and olfactory epithelium).
special sense receptors
the eye include the extrinsic eye muscles, eyelids, conjunctiva, and lacrimal apparatus.
accessory structures
Anteriorly the eyes are protected by
eyelids
The space between the eyelids in an open eye is
palpebral fissure
Projecting from the border of each eyelid
eyelashes
Modified sebaceous glands associated with the eyelid edges are, These glands produce an oily secretion that lubricates the eye
tarsal glands
which are modified sweat glands, lie between the eyelashes, and their ducts open at the eyelash follicles.
Ciliary glands
On the medial aspect of each eye, a raised area containing sebaceous and sweat glands that produce an oily, whitish secretion that also lubricates the eye.
lacrimal caruncle
Lines the eyelids and covers part of
the outer surface of the eyeball, It ends at the edge of the transparent cornea by fusing with the corneal epithelium.
conjunctiva
which helps to lubricate the eyeball and keep it moist.
conjunctiva secretes mucus
Inflammation of the conjunctiva, results in reddened, irritated eyes.
conjunctivitis
its infectious form caused by bacteria or viruses, is highly contagious.
Pinkeye
consists of the lacrimal gland and a number of ducts that drain lacrimal secretions into the nasal cavity.
lacrimal apparatus
located above the lateral end of each eye. They continually release a dilute salt solution (tears) onto the anterior surface of the eyeball through several small ducts.
lacrimal glands
Thus, they cleanse and protect the eye surface as they moisten and lubricate it.
tears
Moves eye laterally
VI (abducens)
Lateral rectus
Moves eye medially
III (oculomotor)
Medial rectus
Elevates eye and turns it medially
III (oculomotor)
Superior rectus
Depresses eye and turns it medially
III (oculomotor)
Inferior rectus
Elevates eye and turns it laterally
III (oculomotor)
Inferior oblique
Depresses eye and turns it laterally
Superior oblique
IV (trochlear)
fluids filled in the eye
humors
the main focusing apparatus of the eye, is supported upright within the eye cavity, dividing it into two chambers.
lens
The outermost layer of the eye
fibrous layer
protective of the fibrous layer, is seen
anteriorly as the “white of the eye.”
sclera
transparent of the fibrous layer, which light
enters the eye.
cornea
The middle of the eyeball, has three distinguishable regions.
vascular layer
Most posterior, a blood rich nutritive tunic that contains a dark pigment. The pigment prevents light from scattering inside the eye.
choroid
which is attached to the lens by a suspensory ligament called the ciliary zonule, and the iris.
ciliary body
The pigmented iris has a rounded opening, through which light passes.
the pupil
The innermost, of the eye is the delicate two-layered retina.
sensory layer
The outer layer of retina, which extends anteriorly only to the ciliary body. Absorb light and prevent light from scattering inside the eye.
pigmented layer
They also act as phagocytes to remove dead or damaged receptor cells and store vitamin A needed for vision.
pigmented layer
The transparent inner of the retina
neural layer
photoreceptors
rods and cones
Electrical signals pass from the photoreceptors via a two-neuron chain
bipolar cells
electrical signals pass before leaving the retina via optic nerve
ganglion cells
interpreted by and the result is vision.
the optic cortex.
it results in a blind spot in our vision
optic disc
are densest at the periphery, or edge, of the retina and decrease in number as the center of the retina is approached and allow us to see in gray tones in dim light, and they provide our peripheral vision.
rods
a tiny pit that contains only cones
fovea centralis
are discriminatory receptors that allow us to see the details of our world in color under bright light conditions and are densest in the center of the retina and decrease in number toward the retinal edge.
cones
responds to a light-trapping dendrite, in which the discs containing the visual pigments
are stacked like a row of pennies.
outer segment
Light entering the eye is focused on the retina by a flexible biconvex crystal-like structure.
lens
the loss of lens transparency, cause vision to become hazy and distorted and can eventually cause blindness.
cataracts
The anterior (aqueous) segment, anterior to the lens, contains a clear watery fluid called…
is similar to blood plasma and is continually
secreted by a special area of the choroid.
aqueous humor
The posterior (vitreous) segment, posterior to the lens, is filled with a gel-like substance called
vitreous humor or vitreous body
Aqueous humor is reabsorbed into the venous blood through, which is located at the junction of the sclera and cornea.
scleral venous sinus, or canal of Schlemm
“vision going gray”- If drainage of aqueous humor is blocked, fluid backs up like a clogged sink. Pressure within the eye may increase to dangerous levels and compress the delicate retina and optic nerve.
glaucoma
When light passes from one substance to another substance that has a different density, its speed changes and its rays are bent, or
refracted
Axons carrying impulses from the retina are bundled together at the posterior aspect of the eyeball and leave the back of the eye as the
optic nerve
This ability of the eye to focus specifically for close objects (those less than 20 feet away) is called
accommodation
The image formed on the retina as a result of the light bending activity of the lens is a
real image
at the optic chiasma, the fibers from the medial side of each eye cross over to the opposite side of the brain. The fiber tracts that result are the
optic tracts
is the loss of the same side of the visual field of both eyes, which results from damage to the visual cortex on one side only (as occurs in some strokes).
Hemianopia
The eye that focuses images correctly on the retina is said to have
emmetropia
occurs when the parallel light rays from distant objects fail to reach the retina and instead are focused in front of it
myopia (nearsighted)
occurs when the parallel light rays from distant objects are focused behind the retina—at least in the resting eye, in which the lens is flat and the ciliary muscle is relaxed
Hyperopia (farsighted)
When the eyes are suddenly exposed to bright light, the pupils immediately constrict; this is the
photopupillary reflex.
which is the reflexive movement of the eyes medially when we view close objects.
convergence
The pupils also constrict reflexively when we view close objects; this provides more acute vision
accommodation pupillary reflex
