1. The Special Senses
Ch. 17

2. Part 1 Objectives
Describe the olfactory receptors.

3. Part 1 – Olfaction: Sense of Smell
Anatomy
3 types of cells
Olfactory receptors – detect the smell and initiate the signal to the brain
Supporting cells – provide physical support, nourishment, and insulation for receptors
Basal cells – make supporting cells
Bowman’s glands
Secrete mucus that moistens olfactory area (boogers)

4. Hyposmia Reduced ability to smell
Affects half of people over age 65 and 75% of people over age 80
Women smell better than men, especially during ovulation
Smoking can impair the sense of smell

5. Part 2 Objectives
Describe the gustatory receptors.

6. Part 2 – Gustation: Sense of Taste
Only 5 primary tastes
Sour, sweet, bitter, salty, umami (meaty or savory)
all flavors are combinations of these tastes
Olfactory and gustatory senses are closely linked – like when you have a cold and food doesn’t taste the same
It is your smell that actually isn’t working properly

7. Gustation Anatomy – p. 470 Taste bud – oval body consisting of cells
Papillae – covered in taste buds
Vallate papillae – 12 very large, circular areas
Fungiform papillae – mushroom-shaped elevations scattered over area of tongue
Foliate papillae – small trenches on tongue – most taste buds are gone by childhood
Filiform papillae – no taste buds – just add friction to tongue making chewing and moving food easier

8. Taste

9. Part 3 Objectives
List and describe the accessory structures of the eye and the structural components of the eyeball.
Discuss image formation by describing refraction and accommodation.
Describe vision abnormalities.

10. Accessory Structures of Eye
Eyelids
Eyelashes
Eyebrows
Lacrimal apparatus
Extrinsic eye muscles

11. Accessory Structures of Eye
Eyelids – palpebrae
Functions:
Shade eyes during sleep
Protect eyes from light
Protect eyes from foreign objects
Spread lubrication over eyeballs
upper eyelid is more moveable – levator palpebrae superioris muscle
Where eyelids meet is called commissure – lateral and medial
Lacrimal caruncle – reddish bump in medial commissure that secretes oil and sweat – causes “sleep” in your eyes

12. Infections Sty – infection in oil gland of eyelash follicle
Chalazion – infection in tarsal glands of eyelid
Tarsal glands secrete fluid onto eye for lubrication

13. Accessory Structures of Eye
Lacrimal apparatus
Produces and drains lacrimal fluid or tears
Eye muscles

14. Anatomy of the Eyeball 2.5 cm in diameter 3 anatomical layers
Fibrous tunic
Vascular tunic
Retina

15. Tunic Layers Outer layer – fibrous Middle layer – vascular
Cornea – transparent, focuses light rays
Sclera – white of the eye
Optic nerve – transmits info to brain
Middle layer – vascular
Choroid coat – contains blood vessels
Ciliary body – holds the lens in place
Lens – focusing
Aqueous humor – fluid surrounding lens
Pupil – opening for light to enter

16. Tunic Layers Inner layer Retina – visual receptor cells
Vitreous humor – fluid supports internal structures

17. Eye

18. Structures of Eyeball

19. Retina Made of cells that are light receptors – photoreceptors
Rods and cones
Rods – black and white
Cones - color
Color blindness
Lack of cones

20. Colorblindness
A genetic trait that affects boys more than girls. The location of the gene is on the X chromosome

21. Image Formation Seeing is like taking a picture
The object must be focused on a “film” – retina
The correct amount of light must be present – pupil
Light bends - refraction

22. Refraction
When light bends as it moves between two mediums – air and water
Images on the retina are upside- down and have right-to-left reversal

23. Image Formation Process
Light hits the cornea and is bent
Light leaves the cornea and is bent again
Light enters the lens where it is focused on the retina
So why don’t we see everything upside- down?
Very early on the brain “learns” how to coordinate the images and make them correct

24. Accommodation Most of the focusing is done by the cornea
25% must be done by the lens
Our lens is convex on both sides in order to produce clear images
The lens will increase its curvature in order to focus all images exactly

25. Animations
body/factfiles/sight/sight_animation.shtml
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26. Abnormalities and Changes
Presbyopia – lens loses elasticity with age
Around age 40 the lens can’t focus near images and people need glasses
Normal eye – emmetropic – can reflect images perfectly of objects 20 ft away
Myopia - near-sightedness
Eyeball is too long for the focusing power of the lens or lens is thicker than normal
Hyperopia – far-sightedness
Eyeball is too short for the focusing power of the lens or lens is thinner than normal

27. Abnormalities

28. Part 4 Objectives
Describe the anatomy of the structures in the three main regions of the ear.
List the major events in the physiology of hearing.

29. Part 4 – Hearing Anatomy of the ear External ear Middle ear Inner ear
Collects sound waves and channels them inward
Middle ear
Conveys sound vibrations to the oval window
Inner ear
Houses the receptors for hearing and equilibrium

30. Ear Anatomy

31. Outer Ear
Auricle (pinna) – flap of elastic cartilage shaped like a trumpet
External auditory canal – curved tube that lies in the temporal bone and leads from the auricle to the eardrum
Eardrum (tympanic membrane) – thin, semitransparent partition between the external auditory canal and the middle ear
Ceruminous glands – produce wax to protect ear from dust and foreign objects

32. Outer Ear

33. Middle Ear Small, air-filled cavity
Contains 3 smallest bones in the body
Auditory ossicles
Malleus, incus, and stapes
contains auditory tube (eustachian tube) – connects middle ear to the throat and nasal cavities
Helps maintain air pressure
Can lead to ear pain during sore throats

34. Middle Ear

35. Inner Ear Labyrinth – communicating chambers and tubes Contains
Semicircular canals – sense of equilibrium
Cochlea – sense of hearing
Organ of Corti – contains hearing receptors, hair cells detect vibrations

36. Inner Ear

37. Hearing Pinna directs sound waves into auditory canal
Sound waves strike ear drum and it vibrates
Auditory ossicles amplify vibrations to cochlea
Organs of Corti contain receptor cells (hair cells) that deform the vibrations
Impulses sent to nerves
Temporal lobe interprets sensory impulses

38. Hearing

39. Part 5 Objectives
Identify the receptor organs for equilibrium, and describe how they function.

40. Part 5 - Equilibrium Balance – 2 types
Static – maintenance of body relative to gravity
Dynamic – maintenance of body in response to sudden movements like rotation, acceleration, and deceleration
Organs that control this are called the vestibular apparatus – all lined with hairs
Saccule and utricle
Semicircular ducts (canals)

41. Equilibrium
The hair cells send signals to the brain that tell it the position of the head
As the hair cells move, the brain can interpret and fix balance