1. Human Anatomy
Special Senses

2. Special Senses Olfaction -- smell Gustation -- taste The Ear
Equilibrium
Hearing
4. Vision

3. 1. Olfaction (Smell)
As few as 4
molecules can
activate neurons

4. 1. Olfaction (Smell)

5. 2. Gustation (Taste) Differential distribution of taste buds

6. 2. Gustation (Taste)
Start w/ 10,000 taste buds and by 50 yo half are lost
Explains why
kids don’t like
spicy food

7. Gustation (Taste)
VII – ant. 2/3
IX – post. 1/3

8. 3. The Ear Is divided into 3 anatomical regions External ear
External auditory meatus to tympanic membrane

9. 3. The Ear
Ceruminous glands secrete cerumen – ear wax

10. 3. The Ear Middle Ear Medial to tympanic membrane
Contains 3 auditory ossicles
Eustachian tube connects middle ear to pharynx

11. Middle Ear

12. Auditory Ossicles Base of stapes fills the oval window
20X amplification
Malleus
Incus
Stapes
Air movement

13. The Ear
Inner Ear
Consists of hollow bony structures filled w/ fluid -- endolymph
Contains the organs of:
Equilibrium – semicircular canals
Hearing -- cochlea

14. The Inner Ear

15. The Inner Ear

16. Semicircular Canals Three Detect motion in three planes: Yes No
Tilting head
from side to side

17. Semicircular Canals Hollow bony tubes Filled with endolymph
Inside lined with hair cells – specialized neurons
Axons, in part, form VIII
Otoliths float across hair cells when head is in motion.

18. Hair Cells

19. Hair Cells

20. Otoliths
Activate hair cells

21. Cochlea Spiral shaped Hollow bony, filled with endolymph
Lined by hair cells
Organ of Corti consists of:
Hair cells
Tectorial membrane – stimulates hair cells

22. Cochlea

23. Cochlea

24. Organ of Corti

25. Organ of Corti
VIII

26. Hair Cells

27. 4. The Eye Organ of vision Slightly smaller than a ping pong ball
Divided into two cavities
Anterior chamber
Posterior chamber
2 chambers separated by the lens
Consists of 3 layers

28. Chambers of the Eye L E N S

29. 4. The Eye Outer wall consists of 3 layers From outer to inner:
Fibrous tunic
Sclera and cornea
Sclera is CT
6 extrinsic eye
muscles attach
Cornea is clear

30. 1. Fibrous Layer
sclera (white of the eye)
cornea

31. 2. Vascular Layer Middle layer Highly vascular
Regulates amount of light into eye – iris
Secretes and absorbs aqueous humor –canal of Schlemm

32. 2. Vascular Layer

33. Iris Iris – pigmented area of middle layer
Its margin defines the pupil.
pupil
iris

34. Pupillary Muscles
parasympathetic
Iris
sympathetic

35. Canal of Schlemm

36. Canal of Schlemm Drains aqueous humor from anterior chamber
Can get blocked
Aqueous humor continues to be produced
Pressure builds up in anterior chamber
Causes pressure in posterior chamber
Retinal blood vessels are compressed and blood flow decreases
Retinal cells die – glaucoma
Result is blindness which is irreversible

37. Glaucoma
pressure

38. 3. Retina Innermost layer – nervous layer
Consists of several layers of cells including modified neurons that react to light
Rods – light-sensitive, allow us to see in low light (125 million/retina)
Cones – detect colors (6 million/retina)

39. 3. Retina
Axons form
Optic n. (II)

40. Optic Nerve (II)
Axons from
ganglion cells

41. Optic Disc
Part of retina where ganglion cell axons leave retina

42. Optic Disc
No rods and cones in optic disc– blind spot

43. Fovea Centralis
Center of retina, site of sharpest vision, has highest concentration of rods and cones

44. Fovea Centralis