1. Nose, Eyes, Ear, and Tongue
Ch 12: Special Senses
Nose, Eyes, Ear, and Tongue

2. External Anatomy of the Eye
Eyelids: Protection, Lubrication
Eyelashes: Protection
Glands: Meibomian and Ciliary
Meibomian: Oil glands, modified sebaceous glands on eyelids
Ciliary: Modified sweat glands.

3. Third eye-lid
Gathers dust
and produces
eye crispies.
In other animals
It can cover the
Eye.

4. What is the Lacrimal apparatus and what does it do?
Lacrimal apparatus. Fig 12.5
Lacrimal glands: release tears
Lacrimal ducts (eyelid) and canals (nose)
Nasolacrimal ducts: empties into the nose
Lacrimal Secretion: Tears have antibodies and lysozyme. Cleans, moistens.
Why is it called a healthy cry?
Lysozyme

5. What are the Muscles of the eye and how do they move it?
Lateral rectus: Moves eye laterally
Medial rectus: Moves eye medially
Superior rectus: Moves eye up
Inferior rectus: Moves eye down
S & I Obliques
Fig 8.15, 197
Fig 12.7, pg 296
Practice using
The Eye Muscles

6. What are the internal structures of the eye? Pg. 295, Fig 12.6
Sclera: white of the eye
Cornea: Clear
Iris: colorful part of the eye
Pupil: Opening of the Iris
Lens and ciliary body: Ciliary body holds the lens in place. The lens focuses light on the back of the eye.

7. What fills the inner eye? Pg 298
Aqueous Humor: Circulates from the cornea to the Lens through the canal of Schlemm.
Vitreous Humor: In the space behind the lens. Keeps the eyes shape, and keeps intraocular pressure stable.
Floaters?
Glaucoma?

9. What lines the back of the eye?
Retina: photoreceptor layer
Rods: Black and white
Cones: Color
Choroid coat: Dark, vascularized layer. Absorbs light. *Non-humans are different
Sclera: Thick, white covering

11. How do you see? Pg. 299 .
How we See
Details of Vision
Adam

12. Light travels through the…
Cornea to the Aqueous humor to the Pupil to the lens.
In the Lens light is bent so that it will hit the Retina of the eye.
To get to the Fovea Centrals light must continue to pass through Vitreous humor.
Light then hits the Retina where Rods and Cones interpret the image and sends it to the Optic nerve to the brain.

13. Where is your vision the best and the worst?
Worst vision: The blind spot. To find your blind spot go to pg 297 in the book.
Blind spot is where the optic nerve takes the image to your brain. There are no rods or cones here. Your brain just fills in the gaps.
Best vision: Fovea Centralis. Lateral to the blind spot, only contains cones. This is the spot of greatest visual acuity.

15. Why do cones see better than rods?
See Fig 12.8
Many Rods, one nerve = blurred edges.
One Cone, one nerve = crisp lines.
Which do you think causes Night Blindness?
What type of cones do you have:
Blue cones: see blue light
Green cones: see green light
Red cones: see red and green light.

16. Component colors are detected by cone cells in the retina
Component colors are detected by cone cells in the retina. All colors in the visible spectrum can be represented as a combination of red, green, and blue. In the retina, a full-color image is broken up into component colors by cone cells specialized to detect red light (long wavelength), green light (med. wavelength), blue light (short wavelength).

17. What is colorblindness?
The lack of a type of cone, or all cones.
Sex-linked gene.
Men suffer from color blindness more often than females.
Vision of the
Colorblind

18. How is Lasik’s performed?
Steps to
LASIK
Surgery
Steps to
LASIK
Surgery

19. Illusions
More Illusions

20. Functions: Hearing and Equilibrium…………….
The Ear Pg. 302 & 303
Functions: Hearing and Equilibrium…………….

22. External Ear
How the
Ear hears.
Auricle
External Auditory Meatus-2.5 cm long leads to Middle ear

23. The Middle Ear Tympanic Cavity: air-filled space
Tympanic Membrane- ear drum
Pressure changes cause it to vibrate, enhances the sound wave
Auditory Ossicles: smallest bones in the body. Malleus, incus, and stapes.
The Stapes vibrate at the oval window causing fluid in the inner ear to move, stimulating hearing receptors.

25. STAPES

26. INCUS

27. MALLEUS

28. Auditory tube mucous membranes connect directly with the middle ear linings. Thus, mucous membrane infections of the throat may spread through these tubes and cause a middle ear infection.
Question: Why is it important to keep a babies head up when bottle feeding?
How the
Tubes work
Xylitol gum and chewing it could help prevent ear infections.

29. Inner Ear. Pg. 304 Cochlea: hearing
Oval Window: the stapes vibrates this in order for your nerves to fire and for you to hear sound.
Quick Review
Sound on Cochlea
Review of the Ear:
In depth on Cochlea
And Hearing

30. Inner Ear: pg. 306 - 307 Semicircular Canals: maintain equilibrium
The vestibular system

31. Hearing Illusions

32. The Nose. Fig 12.3 Smells using Olfactory Receptors
Sex and
Smell
Smells using Olfactory Receptors
Yellow-brown mass located at the top of each nasal cavity
Size of a postage stamp.
Factoid:
These swirl the
Air so that
Dust and germs
Stick to the
Mucus.
How we smell

33. How do olfactory receptor cells smell?
Use Olfactory Hairs
Must be covered in mucus
Chemicals dissolve in mucus
Trigger nerve
Olfactory Nerve
Connects to the Olfactory Bulb in Brain. Travels to temporal lobe for interpretation.
Tied to the limbic system (emotional system) of the brain. Smells stimulate memories.

34. Interesting Nose facts
Olfactory neurons that are over stimulated shut off. (Can’t smell X after a while.)
Anosmias: loss of smell due to head injuries, nasal cavity inflammation (cold, allergy, smoking) or age.
Often caused by a zinc deficiency
Olfactory auras: epileptics may have smell hallucinations before a seizure.
Because dust in space does not settle Austronoauts sneeze about 100 times a day!

35. The Tongue. Fig. 12.4 . Factoid: You can detect and distinguish
between 10,000
odors, but
only 5 tastes. .

37. How Do You Taste?
Gustatory cells- respond to chemicals that are dissolved in saliva
Taste buds- receptor sites for tastes. Most are on the tongue. Some are on the roof of the mouth and cheeks
Papillae- on the sides of this structure is where taste buds are found
How do you
Taste?

38. Basic Taste Sensations
Sweet- sugar, OH- groups
Sour- acidic, H+
Umami- meaty or savory
Bitter- alkaloid bases, very few H+ bonds
Salty- metal ions
The science Of
Picky Eaters

39. What effects taste?
Temperature
Smell
Texture
Genetics