Chapter 17: Special Senses (Vision) Flashcards
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
is the science that deals with the eyes and their
disorders
OPTHAMOLOGY
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
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
include the eyelids, eyelashes, eyebrows, the
lacrimal (tear-producing) apparatus, and extrinsic
eye muscles.
ACCESSORY STRUCTURES OF THE EYE
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
more movable than the lower and contains
in its superior region the levator palpebrae
superioris.
Upper Eyelid
more movable than the lower and contains
in its superior region the levator palpebrae
superiori
Palpebral Fissure
narrower and closer to the temporal bone,
Lateral Commissure
o broader and nearer the nasal bone. In the
_______ is a small, reddish
elevation
Medial Commissure
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
o thick fold of connective tissue that gives
form and support to the eyelids
Tarsal Plate
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
Infection of the tarsal glands produces a
tumor or cyst on the eyelid
Chalazion
is a thin, protective mucous membrane
composed of nonkeratinized stratified
squamous epithelium with numerous goblet
cells that is supported by areolar connective
tissue
Conjunctiva
lines the inner aspect of the eyelids
Palpebral Conjunctiva
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
which project from the border of each eyelid
Eyelashes
which arch transversely above the upper
eyelids, help protect the eyeballs from
foreign objects, perspiration, and the direct
rays of the sun
Eyebrows
Sebaceous glands at the base of the hair
follicles of the eyelashes
o release a lubricating fluid into the follicles
Sebaceous Ciliary Glands
Infection of these glands, usually by
bacteria, causes a painful, pus-filled
swelling
Sty
a group of structures that produces and drains
lacrimal fluid or tears in a process called
lacrimation.
THE LACRIMAL APPARATUS
each about the size and shape of an
almond, secrete lacrimal fluid, which drains
into 6–12 excretory lacrimal ducts
Lacrimal Glands
empty tears onto the surface of the
conjunctiva of the upper lid.
Excretory Lacrimal Ducts
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