Download Special Senses

Anatomy & Physiology 120
Lab 10: Special Senses
Eyes & Ears
Things to know...
• Be able to Identify all the following features of
the eye by using:
– Diagrams
– Models
– Preserved beef eye
• Be able to Identify all the following features of
the ear using
– Diagrams
– Models
The Eye
• Is hollow and spherical (~2.5 cm diameter)
– Large (main) hollow space - filled with a fluid =
helps maintain the eyes shape and gives support
– Two spaces in the eye (Anterior cavity & Posterior cavity)
• 3 layers inner, middle, outer tunic
• Today we will be dissecting a cow eye
(work in groups of 4 or 5)
Muscles of the Eye
(Extrinsic eye muscles)
A) Lateral rectus
Medial rectus – Opposite the Lateral rectus
B) Inferior rectus
Rectus - A straight muscle
C) Superior rectus
Oblique - Having a slanting
or sloping direction
D) Inferior oblique
E) Superior oblique
Six extrinsic eye muscles –
Able to move the eye in
various directions.
Accessory Structures of the Eye
• Eyelids – Skin, muscle, connective tissue & conjunctiva
– Is the thinnest skin of the body & moved by the
orbicularis oculi muscle
• Conjunctiva – Mucus membrane lining the inside surface
of the eyelids (folds back covering some of the eyeball)
• The Lacrimal Apparatus
–
–
–
–
Lacrimal gland – Makes tears
Lacrimal canals (canaliculi) – Collect tears (superior & inferior)
Tears then flow down and
Lacrimal sac
empty into the nasal cavity
Nasolacrimal duct
The Lacrimal Apparatus
Lacrimal gland
Lacrimal canals
(Canaliculi)
Lacrimal sac
Nasolacrimal duct
8
Sclara
Whites of the eye
1) Cornea – Window of the eye
2) Iris - “the color of your eyes”
3) Pupil – Where light enters the eye
4) Lens - focus light onto the retina
5) Conjunctiva - thin, transparent tissue that covers the outer surface
of the visible eye & covers the eye lids
6) Retina - multi-layered sensory tissue that lines the back of the eye
7) Optic nerve - transmits electrical impulses from the retina to the
brain
8) Sclera - commonly known as "the white of the eye.“ Covers the
entire eye
• Choroid - lies between the retina and
sclera. It is composed of layers of blood
vessels that nourish the back of the eye.
– Ciliary body: behind the iris.
Suspensory ligaments hold the lens in
place
– Ciliary muscle: change the shape of
the lens
– Iris: “the color of your eyes”
thin diaphragm that controls how
much light can enters you eye.
Pupil: Where light enters the eye
JirehDesign.com
2 Cavities of the Eye
Anterior cavity – Contains Aqueous humor (watery)
Posterior cavity – Contains Vitreous humor (jelly like)
Retina – visual receptors (continuous with the optic nerve)
Optic disk – (1) Nerve fibers leave the eye
Anterior cavity
“the blind spot”
Posterior cavity
Macula lutea – (2) In the central region of the eye
Fovea centralis – (3) Region that
produces the sharpest vision
Optic nerve – Lead from the eyes to the brain
1
2
3
External Ear
The Ear
Middle Ear
Auricle
Auditory tube
External auditory meatus
Auditory ossicles
Malleus
Tympanic membrane
Tympanic
Membrane
Auricle
Incus
Malleus
Incus
Stapes
Semicircular
canals
Stapes
Oval window
Inner Ear
1) Cochlea
2) Semicircular
Cochlea
Auditory tube
External auditory meatus
Round window
Canals
The Inner Ear
A complicated system of sacs
and tubes filled with a fluid
Bony labyrinth
Membranous
labyrinth
• Osseous (bony) Labyrinth
the outer most layer
• Membranous Labyrinth
the inner most layer
• Vestibule (Enlarged area of the labyrinth)
used to sense Static equilibrium
– Utricle – Upper portion
– Saccule – Lower portion
Semicircular canals (balance)
Ampullae- at the base of each canal
where the sensory organ lies
Ampulla
Cochlear
duct
How you hear…..
Hair cells
Tectorial membrane
(External ear) Sound waves 
EAM  Ear drum 
(Middle ear) Malleus  Incus 
Stapes
Basilar Membrane
* (Internal ear) The sound waves
- Oval window  Sclara vestibuli 
Vestibular membrane  Tectoral
membrane  hair cells
Excess vibrations  through the
basilar Membrane Sclara
tympani  Round window
Today’s activity - Ear
• Label diagrams pg 198 – 200
• Hearing tests
– Rinne test #3 pg 199 (for conduction deafness)
– Weber test #4 pg 200 (for sensory deafness)
• Complete parts A & B
Cross section of the cochlea
Today’s activities - Eye
• Label diagrams
• Lab: Parts A (1-13 & 15) &
B (the best that you can) of the lab report
• Dissect the cow eye and locate features
• Lab 30: Part A & B (1 & 2 only)
• Do the following 5 tests
– Visual acuity
- Blind spot
- Blind spot
– Color blindness - Astigmatism
Visual Tests
• Visual acuity – Snellen eye chart (normal vision)
– #8 – 20/20 vision (stand 20 feet away and read it)
– #1 – 20/200 (stand 200 feet away and read it)
• Stand 20 feet away and read the smallest line as
possible (Covering one eye) **repeat & record**
• Astigmatism – (defect in the curvature of the eye)
– Normal eye – sees sharply focused and dark lines
– Abnormal eye – some will be sharp & dark while some are not
• Stand 20 ft away and focus on the center (one eye)
**repeat and record**
• Accommodation test – focusing for close vision
– Read #3 about accommodation
– Hold a meter stick against your chin / Close one eye / &
move the card toward the subject
– Locate the point where the subject where the word sharply
focuses = near point accommodation **record & repeat**
• Color vision test – (X-linked genetic)
– Look at the color test plates (at least 30 inches)
– Responses should occur with in 3 sec
– Record the results
• Blind spot – (optic nerve – no receptors)
– Close one eye / Hold the card 35cm away / stare at the + /
move the figure closer until the dot disappears
Dissection of the Cow Eye
• First - Locate the cornea, sclera and iris
– The cornea from a fresh eye is white
– The cornea from a preserved eye is opaque
• Be careful when making the first cut
(around the margin of the cornea)
– Try not to damage the inside
• Please read and follow the
instructions!!!!
• Trash all bio waste in the marked containers
– No paper towels
On-line Cow eye dissection
www.exploratorium.edu/learning_studio
/cow_eye/step01.html
Nice site for Eye pics
www.stlukeseye.com
education.vetmed.vt.edu/.../EXAMPLES/Excorti.htm
http://www.artandmedicine.com/biblio/images/rud
inger/Rudinger5.jpg
http://www.brainconnection.com/med/medart/l/coc
hlea-xsection.jpg
www.entnet.org/healthinfo/ears/ear.cfm
www.freewebs.com/.../creatoroftheringsandof.htm
http://www.unmc.edu/eye/Media/retina.jpg
www.99main.com/~charlief/Blindness.htm
http://utopia.duth.gr/~adamand/destruction/ima
ges/eye.jpg
www.discovery.com/.../skinny1.html