Download The Eye and Ear (model-based undergrad

Lab 8
The Eye and The Ear
Exercise 1 – The eye
Goals: N Become acquainted with the structures of the eye
N Review key structures and concepts of the visual system
Look at the plastic models of the eyeballs.
1. On the external surface of the eyeball:
a. What is the name of the “white” of the eye?
b. What is the name of the clear, bulging anterior portion of the eye?
2. Open the model of the eye and identify the ciliary body, the iris, and the lens. Two
smooth muscles are present within the iris: sphincter pupillae and dilator pupillae.
Note: the terms sphincter pupillae and constrictor pupillae are two names for the same
structure. One smooth muscle is present within the ciliary body: the ciliary muscle. The
dilator pupillae receives sympathetic innervation while sphincter pupillae and the
ciliary muscle receive parasympathetic. What cranial nerve provides that
parasympathetic innervation?
3. Identify the retina.
a. What layer of the eyeball is situated between the sclera and the retina?
b. What is the name of the location where the optic nerve exits the eyeball? No
photoreceptor cells (rods or cones) are present at this location.
c. What is the name of the portion of the retina where most of the cones are
concentrated? What is the name for the depression within this area where only
cones can be found?
4. Identify the chambers within the eyeball: vitreous, posterior and anterior. Note: the
most posterior chamber is the vitreous chamber!
a. What fills the vitreous chamber?
b. What fluid fills the posterior and anterior chambers?
c. Where is the fluid of the posterior and anterior chambers produced and how does
it drain out of the eyeball?
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Exercise 2 – The ear
Goals: N Become acquainted with the structures of the ear
N Review key structures and concepts of the auditory system
The ear is divided into three anatomical regions: the external ear, the middle ear, and the
internal ear.
The external ear consists of the auricle and the external auditory canal. On the auricle,
identify the helix, antihelix, lobule (ear lobe), and tragus. For parts of the auricle not visible
on the models, identify them on the ear of yourself, another student, or a TA.
The middle ear is separated from the external ear by the tympanic membrane and consists of
an air-filled tympanic cavity. Identify the tympanic membrane and tympanic cavity on the
models.
1) What are the names of the three auditory ossicles? List them from lateral (at the tympanic
membrane) to medial.
2) What is the name of the tube that connects the tympanic cavity to the nasopharynx?
Identify this tube on the models.
3) The medial wall of the tympanic cavity abuts against the inner ear. What are the two
windows in this wall? What window does the stapes sit in?
The inner ear is the deepest part of the ear. It is comprised of a labyrinth of bony canals and
chambers. The labyrinth of the inner ear is comprised of three parts, the semicircular canals,
the vestibule, and the cochlea. Membranous sacs and tubes (called the membranous
labyrinth) lie within the bony labyrinth.
1) Identify the vestibule.
a. What parts of the membranous labyrinth are housed in the vestibule?
b. What is their function?
2) Identify the semicircular canals. The membranous semicircular ducts are housed
within the semicircular canals. Identify the anterior, posterior, and lateral canal. Observe
that they open into the vestibule.
a. What structure located within the vestibule do the semicircular ducts emerge
from?
b. What is their function?
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3) Identify the cochlea. It is connected to the vestibule and abuts the tympanic cavity. The
cochlea resembles a small snail shell as it is a coiled canal. The part of the membranous
labyrinth of the cochlea is called the cochlear duct. The cochlear duct and a spur of
bone divide the cochlea into two parts: the scala vestibuli and the scala tympani.
a. At what part of the bony ear does scala vestibuli begin?
b. What membrane forms a “wall” of the scala vestibuli?
c. Which window does the scala tympani end at?
d. What membrane forms a “wall” of the scala tympani?
e. What is the name of the apex of the cochlea where the scala tympani and scala
vestibuli are continuous with one another?
f. What organ is housed in the cochlear duct and what membrane forms a tent over
it?