Chapter 17: Special Senses (Vision) Flashcards by Lorenz Angelo C. Sarmiento

 the act of seeing, is extremely important to human
survival because it allows us to view potentially
dangerous objects in our surroundings.
 More than half the sensory receptors in the human
body are located in the eyes, and a large part of the
cerebral cortex is devoted to processing visual
information.

VISION

How well did you know this?

Not at all

Perfectly

is the science that deals with the eyes and their
disorders

OPTHAMOLOGY

How well did you know this?

Not at all

Perfectly

is energy in the form of waves that radiates from the
sun. There are many types of electromagnetic
radiation, including gamma rays, x-rays, UV rays,
visible light, infrared radiation, microwaves, and radio
waves.

ELECTROMAGNETIC RADIATION

How well did you know this?

Not at all

Perfectly

CTROMAGNETIC SPECTRUM
 This range of _____________
 The distance between two consecutive peaks of an
electromagnetic wave is the wavelength.
Wavelengths range from short to long; for example,
gamma rays have wavelengths smaller than a
nanometer, and most radio waves have wavelengths
greater than a meter

electromagnetic radiation

How well did you know this?

Not at all

Perfectly

include the eyelids, eyelashes, eyebrows, the
lacrimal (tear-producing) apparatus, and extrinsic
eye muscles.

ACCESSORY STRUCTURES OF THE EYE

How well did you know this?

Not at all

Perfectly

The upper and lower eyelids, or palpebrae
(singular: palpebral)
o shade the eyes during sleep, protect the
eyes from excessive light and foreign objects, and spread lubricating secretions
over the eyeballs.

EYELIDS

How well did you know this?

Not at all

Perfectly

more movable than the lower and contains
in its superior region the levator palpebrae
superioris.

Upper Eyelid

How well did you know this?

Not at all

Perfectly

more movable than the lower and contains
in its superior region the levator palpebrae
superiori

 Palpebral Fissure

How well did you know this?

Not at all

Perfectly

narrower and closer to the temporal bone,

Lateral Commissure

How well did you know this?

Not at all

Perfectly

o broader and nearer the nasal bone. In the
_______ is a small, reddish
elevation

Medial Commissure

How well did you know this?

Not at all

Perfectly

which contains sebaceous (oil) glands and
sudoriferous (sweat) glands. The whitish
material that sometimes collects in the
medial commissure comes from these
glands.

 Lacrimal Caruncle

How well did you know this?

Not at all

Perfectly

o thick fold of connective tissue that gives
form and support to the eyelids

Tarsal Plate

How well did you know this?

Not at all

Perfectly

Embedded in each tarsal plate is a row of
elongated modified sebaceous glands
o Or Meibomian glands
o secrete a fluid that helps keep the eyelids
from adhering to each other

Tarsal Glands

How well did you know this?

Not at all

Perfectly

Infection of the tarsal glands produces a
tumor or cyst on the eyelid

 Chalazion

How well did you know this?

Not at all

Perfectly

is a thin, protective mucous membrane
composed of nonkeratinized stratified
squamous epithelium with numerous goblet
cells that is supported by areolar connective
tissue

 Conjunctiva

How well did you know this?

Not at all

Perfectly

lines the inner aspect of the eyelids

 Palpebral Conjunctiva

How well did you know this?

Not at all

Perfectly

passes from the eyelids onto the surface of
the eyeball, where it covers the sclera (the
“white” of the eye) but not the cornea, which
is a transparent region that forms the outer
anterior surface of the eyeball.

Bulbar Conjunctiva

How well did you know this?

Not at all

Perfectly

which project from the border of each eyelid

Eyelashes

How well did you know this?

Not at all

Perfectly

which arch transversely above the upper
eyelids, help protect the eyeballs from
foreign objects, perspiration, and the direct
rays of the sun

Eyebrows

How well did you know this?

Not at all

Perfectly

Sebaceous glands at the base of the hair
follicles of the eyelashes
o release a lubricating fluid into the follicles

Sebaceous Ciliary Glands

How well did you know this?

Not at all

Perfectly

Infection of these glands, usually by
bacteria, causes a painful, pus-filled
swelling

 Sty

How well did you know this?

Not at all

Perfectly

a group of structures that produces and drains
lacrimal fluid or tears in a process called
lacrimation.

THE LACRIMAL APPARATUS

How well did you know this?

Not at all

Perfectly

each about the size and shape of an
almond, secrete lacrimal fluid, which drains
into 6–12 excretory lacrimal ducts

Lacrimal Glands

How well did you know this?

Not at all

Perfectly

empty tears onto the surface of the
conjunctiva of the upper lid.

 Excretory Lacrimal Ducts

How well did you know this?

Not at all

Perfectly

o (singular: punctum) o From here the tears pass medially over the anterior surface of the eyeball to enter two small openings o Tears then pass into two ducts, the superior and inferior lacrimal canaliculi, which lead into the lacrimal sac (within the lacrimal fossa) and then into the nasolacrimal duct.

Lacrimal Puncta

This duct carries the lacrimal fluid into the nasal cavity just inferior to the inferior nasal concha where it mixes with mucus.

 Nasolacrimal ducts

An infection of the lacrimal sacs.

 Dacryocystitis

The adult eyeball measures about 2.5 cm (1 in.) in diameter  Anatomically, the wall of the eyeball consists of three layers

(1) fibrous tunic, (2) vascular tunic, and (3) retina (inner tunic).

the superficial layer of the eyeball and consists of the anterior cornea and posterior sclera.

FIBROUS TUNIC

a transparent coat that covers the colored iris

Cornea

the “white” of the eye, is a layer of dense connective tissue made up mostly of collagen fibers and fibroblasts o The sclera covers the entire eyeball except the cornea; it gives shape to the eyeball, makes it more rigid, protects its inner parts, and serves as a site of attachment for the extrinsic eye muscles

Sclera

or (canal of Schlemm). A fluid called aqueous humor, which will be described later, drains into this sinus

Scleral Venous Sinus

Or uvea is the middle layer of the eyeball. It is composed of three parts: choroid, ciliary body, and iris

VASCULAR TUNIC

the posterior portion of the vascular tunic, lines most of the internal surface of the sclera. o Its numerous blood vessels provide nutrients to the posterior surface of the retina. The choroid also contains melanocytes that produce the pigment melanin, which causes this layer to appear dark brown in color. Melanin in the choroid absorbs stray light rays, which prevents reflection and scattering of light within the eyeball.

 Choroid

In the anterior portion of the vascular tunic, the choroid becomes the ciliary bod. It extends from the ora serrata

Ciliary Blood

o the jagged anterior margin of the retina, to a point just posterior to the junction of the sclera and cornea

Ora Serrata

are protrusions or folds on the internal surface of the ciliary body. They contain blood capillaries that secrete aqueous humor

Ciliary Processes

Extending from the ciliary process o or suspensory ligaments that attach to the lens.

Zonular Fibers

a circular band of smooth muscle. Contraction or relaxation of the ciliary muscle changes the tightness of the zonular fibers, which alters the shape of the lens, adapting it for near or far vision.

Ciliary Muscles

the colored portion of the eyeball, is shaped like a flattened donut. It is suspended between the cornea and the lens and is attached at its outer margin to the ciliary processes

Iris

o the hole in the center of the iris. The pupil appears black because, as you look through the lens, you see the heavily pigmented back of the eye (choroid and retina)

Pupil

or sphincter pupillae o causing a decrease in the size of the pupil (constriction).

Circular muscles

or dilator pupillae of the iris to contract, causing an increase in the pupil’s size (dilation).

Radial Muscles

The third and inner layer of the eyeball  lines the posterior three-quarters of the eyeball and is the beginning of the visual pathway

RETINA

is the site where the optic (II) nerve exits the eyeball.

Optic Disc

a branch of the ophthalmic artery

Central Retinal Artery

o Branches of the central retinal artery fan out to nourish the anterior surface of the retina; the central retinal vein drains blood from the retina through the optic disc  The retina consists of a pigmented layer and a neural layer

Central Retinal Vein

a sheet of melanin-containing epithelial cells located between the choroid and the neural part of the retina.

Pigmented Layer

a multilayered outgrowth of the brain that processes visual data extensively before sending nerve impulses into axons that form the optic nerve.

Neural (sensory) Layer

the photoreceptor cell layer, the bipolar cell layer, and the ganglion cell layer- are separated by two zones, the outer and inner synaptic layers, where synaptic contacts are made

Three distinct of retinal neurons

Two other types of cells present in the bipolar cell layer of the retina o These cells form laterally directed neural circuits that modify the signals being transmitted along the pathway from photoreceptors to bipolar cells to ganglion cells.

Horizontal cells and Amacrine cells

o allow us to see in dim light, such as moonlight. Because rods do not provide color vision, in dim light we can see only black, white, and all shades of gray in between.

 Rods

Brighter lights stimulate o produce color vision. Three types of cones are present in the retina: (1) blue cones, which are sensitive to blue light, (2) green cones, which are sensitive to green light, and (3) red cones, which are sensitive to red light.

Cones

also called the blind spot

Optic Disc

or yellow spot is in the exact center of the posterior portion of the retina, at the visual axis of the eye.

Macula lutea

a small depression in the center of the macula lutea, contains only cones.

Fovea Centralis

Behind the pupil and iris, within the cavity of the eyeball

LENS

arranged like the layers of an onion, make up the refractive media of the lens, which normally is perfectly transparent and lacks blood vessels

Crystallins

The lens divides the interior of the eyeball into two cavities: the anterior cavity and vitreous chamber.

INFERIOR OF THE EYEBALL

the space anterior to the lensconsists of two chambers

 Anterior Cavity

o lies between the cornea and the iris

Anterior Chamber

o lies behind the iris and in front of the zonular fibers and lens

Posterior chamber

o a transparent watery fluid that nourishes the lens and cornea.

Acqueous Humor

which lies between the lens and the retina

Vitreous Chamber

a transparent jellylike substance that holds the retina flush against the choroid, giving the retina an even surface for the reception of clear images

Vitreous Body

a narrow channel that is inconspicuous in adults and runs through the vitreous body from the optic disc to the posterior aspect of the lens.

Hyaloid Canal

The pressure in the eye o produced mainly by the aqueous humor and partly by the vitreous body; normally it is about 16 mmHg (millimeters of mercury

Intraocular Pressure

This increase in the curvature of the lens for near vision o The near point of vision is the minimum distance from the eye that an object can be clearly focused with maximum accommodation. This distance is about 10 cm (4 in.) in a young adult.

 Accommodation

is a narrowing of the diameter of the hole through which light enters the eye due to the contraction of the circular muscles of the iris.

 Constriction of the Pupil

o provide output from the retina to the brain.

 Optic (II) Nerve

a crossing point of the optic nerves

 Optic Chiasm

After passing through the optic chiasm, the axons, now part of the optic tract, enter the brain and most of them terminate in the lateral geniculate nucleus of the thalamus.

Optic Tract

they synapse with neurons whose axons form the optic radiations

 Lateral Geniculate Nucleus

project to the primary visual areas in the occipital lobes of the cerebral cortex

Optic radiations

visual perception begins

Primary Visual Areas

which control the extrinsic eye muscles

Super Colliculi

which control pupillary and accommodation reflexes.

Pretectal Nuclei

o Everything that can be seen by one eye is that eye’s ________

visual field.