1. Notes: Special Senses
Chapter 8

3. Anatomy of the EYE

4. External Eye Structures
External & Accessory structures include:
Eyelids
Conjunctiva
Lacrimal apparatus
Extrinsic eye muscles
Tendon of levator
palpebrae superioris
Orbicularis
oculi
Eyelid
Eyelash
Cornea
Conjunctiva

5. Eyelids Protects the anterior of the eyes
Eyelashes project from the border of each eyelid
Tarsal glands on the edges of the eyelids produce an oily secretion that lubricates the eye

6. Conjunctiva
This is a delicate membrane that lines the eyelids and covers a portion of the eyeball
Function: secrete mucus to help lubricate the eyeball and keep it moist.

7. Conjunctiva
Conjunctivitis is due to inflammation of the conjunctiva. It results in reddened irritated eyes
Pink Eye is the infection form that is caused by bacteria or viruses and is highly contagious.

8. Lacrimal Apparatus
Produce a saline solution, which washes and lubricates the eyeball.
Tears are an increase in lacrimal secretions
Makes your nose run because it drains into nasal cavity.
Lacrimal gland
Superior and
inferior canaliculi
Lacrimal sac
Nasolacrimal
duct

9. Extrinsic Eye Muscles
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
These are attached to the outer surface of the eye
Are responsible for allowing the eye to follow a moving object.
Medial
rectus
Superior
rectus
Superior
oblique
Lateral
rectus
(cut)
Inferior rectus
Inferior oblique

10. Internal Eye Structures
The eyeball is a hollow sphere.
Its wall is made of 3 layers or tunics
The inside is filled with fluids called humors.
The lens is the main focusing apparatus and divides the eye into 2 chambers

11. Structure of the Eye Wall has three (3) layers: Outer fibrous tunic
Middle vascular tunic
Inner sensory tunic
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Lateral rectus
Retina
Ciliary body
Choroid coat
Suspensory
ligaments
Sclera
Vitreous humor
Iris
Lens
Fovea centralis
Pupil
Cornea
Aqueous
humor
Anterior
chamber
Anterior
cavity
Optic nerve
Posterior
chamber
Optic disc
Posterior cavity
Medial rectus

12. Outer Fibrous Tunic Consists of the sclera and the cornea.
The sclera is a thick, glistening white connective tissue.
Found on the posterior of the eye.
It is known as the “white of the eye”.

13. Outer Fibrous Tunic The Cornea is located on the anterior of the eye
This part is clear and it is where light enters
It is the most exposed part of the eye and vulnerable to damage, but it is quick to heal.

14. Middle Vascular Tunic Posterior Portion Provides blood supply
Choroid
Posterior Portion
Provides blood supply
Contains dark pigments to absorb extra light

15. Middle Vascular Tunic Ciliary body Anterior portion Pigmented
Holds lens
Moves lens for focusing
Ciliary muscle
fibers contracted
Suspensory
ligaments relaxed
Lens thick
(a)
Ciliary muscle
fibers relaxed
Suspensory
ligaments taut
Lens thin
(b)

16. Middle Vascular Tunic Iris Anterior portion Pigmented
Controls light intensity by adjusting size of pupil
Pupil
The rounded opening in the iris
Sympathetic
motor nerve
fiber
In dim light
Radially arranged
Smooth muscle fibers
of the iris
Parasympathetic
ganglion
Circularly arranged
smooth muscle fibers
of the iris
Pupil
Parasympathetic
motor nerve fiber
In normal light
In bright light

17. Inner Sensory Tunic Includes the RETINA that has two layers
The pigmented layer absorbs extra light. The cells of the retina also remove dead or damaged receptor cells. They also help to store vitamin A that is needed for vision.

18. Inner Sensory Tunic
The neural layer of the retina has photoreceptors that respond to light.
RODS- allow us to see in dim light and are responsible for our peripheral vision
CONES- allow us to see the details of our world in color and under bright light conditions.

19. Rods & Cones in Retina

20. Inner Sensory Tunic Blind Spot:
This is the spot where the optic nerve leaves the eyeball. There are no photoreceptors here so when light passes over this optic disc the object dissappears.

21. Inner Sensory Tunic Fovea Centralis-
A tiny pit that contains only cones. It is the area of greatest visual acuity or your point of sharpest vision.
Center of the retina

22. Inner Sensory Tunic Lens-
Is a flexible biconvex crystal-like structure.
Held in place by a ligament from the ciliary body.
It divides the eye into two chambers
Anterior segment contains a clear watery fluid called aqueous humor.
Posterior segment is filled with a gel-like vitreous humor.
Both help to provide pressure in the eye.

23. Aqueous & Vitreous Humor
Aqueous Humor
Vitreous humor

24. Lens Cornea Anterior chamber Iris Posterior chamber Suspensory
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Cornea
Anterior chamber
Iris
Posterior
chamber
Suspensory
ligaments
Ciliary process
Ciliary muscles
Conjunctiva
Lens
Vitreous
humor
Sclera

25. Lens
LENS
biconvex: convex on both sides
can change shape to focus

26. Lens AQUEOUS HUMOR liquid between cornea and iris
maintains shape of cornea
produced by the ciliary body
VITREOUS HUMOR
clear, jelly-like liquid inside the eyeball
helps maintain spherical shape of eye

27. Presbyopia
ciliary muscles lose power and the person becomes farsighted – convex reading glasses help this
genetic disorder – person missing cones
Colorblindness
most colorblind people are red-green colorblind
aqueous humor does not drain
Glaucoma
results in pain and can lead to blindness as pressure inside eyeball damages retina

29. Cataracts
lens becomes cloudy – usually with age

30. Cataract Vision

31. Anatomy of the EAR

32. External Ear (3 parts) Auricle (or pinna)-
Is what most people call the ear.
shell-shaped structure that collects and directs sound waves into the auditory canal.

33. External or Outer Ear
External Acoustic Meatus (aka the auditory canal)
Passage to eardrum
Short, narrow chamber which secretes earwax to trap foreign bodies and repel insects.

34. External or Outer Ear Tympanic Membrane, or eardrum
Sound waves hit the eardrum causing it to vibrate.
It separates the external ear from the middle ear.

35. Middle Ear Is an Air-filled space in temporal bone
Is connected to the throat by the eustachian tube.
This equalizes pressure in the ear.
In infants it is very horizontal so that is why they should not lay down and drink
Sore throats in children also cause middle ear infections and may need to be surgically fixed with a tube.

36. Middle Ear Has the 3 smallest bones in the body called ossicles:
Vibrate in response to tympanic membrane
Hammer, anvil and stirrup
Oval window
Opening in wall of tympanic cavity
Stirrup vibrates against it to move fluids in inner ear

37. Inner Ear Made of a bony labyrinth that is divided into 3 parts:
Cochlea
Functions in hearing
Semicircular canals
Functions in equilibrium
Vestibule
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Bony labyrinth
Perilymph
Membranous labyrinth
Endolymph
Bony labyrinth
(contains perilymph)
Membranous labyrinth
(contains endolymph)
Semicircular
canals
Utricle
Vestibular nerve
Saccule
Cochlear nerve
Scala
vestibuli (cut)
Scala
tympani (cut)
Cochlear
duct (cut)
containing
endolymph
Ampullae
Oval
window
Vestibule
Round
window
Maculae
Cochlea
(a)

38. Hearing

39. Mechanism of Hearing
Sound waves reach the cochlea through vibrations of the eardrum, ossicles, and oval window
This sets the fluid in the inner ear into motion
Hair cells in the spiral organ of Corti are stimulated and transmit impulses to the cochlear nerve.

40. Animation: Effect of Sound Waves on Cochlear Structures
Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at

41. Equilibrium

42. Sense of Equilibrium Static equilibrium
Receptors called maculae are responsible for our static equilibrium
Senses position of head when body is not moving

43. Sense of Equilibrium Dynamic Equilibrium – balance and movement
Semicircular canals
Senses rotation and movement of head and body

44. Ear Disorders Deafness - hearing loss of any kind 2 types
Conduction Deafness
Sensorineural Deafness
something interferes with sound waves entering the ear
EX: earwax, ruptured eardrum, infection
damage to receptor cells in organ of Corti, cochlear nerve, or neurons

45. Ear Disorders Motion Sickness
impulses from ear nerves do not agree with visual input
can result in dizziness, nausea, loss of balance

46. NOTES: Chemical Senses

47. CHEMORECEPTORS Chemoreceptors:
The receptors for taste and smell are classified as chemoreceptors because they respond to chemicals dissolved in liquids

48. Sense of Smell

49. Sense of Smell Olfactory organs
Are located in a postage stamped sized area in the roof of the nasal cavity.
Contain olfactory receptors and supporting epithelial cells

50. The Nose- Smelling & Tasting
2 nasal chambers called nostrils
Separated by nasal septum
Receptors use cilia to capture smell
Nose also helps with taste
External nose is part bone and part cartilage

51. Olfactory Receptors Nerve fibers within the olfactory bulb Olfactory
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Nerve fibers within
the olfactory bulb
Olfactory
tract
Olfactory
bulb
Cribriform
plate
Olfactory area of
nasal cavity
Superior nasal
concha
Nasal cavity
Cilia
Olfactory
receptor cells
Columnar
epithelial cells
Cribriform
plate
(a)
(b)

52. Olfactory Nerve Pathways
Once olfactory receptors are stimulated, nerve impulses travel through
Olfactory nerves olfactory bulbs olfactory tracts limbic system (for emotions) and olfactory cortex (for interpretation)

53. Smells and Emotion
Olfactory impressions are long-lasting and very much a part of our memories and emotions.
There are hospital smells, school smells, baby smells, travel smells.
Smells may remind you of specific people or events.

54. Olfactory Stimulation
Olfactory receptors are extremely sensitive and can by activated by just a few molecules.
Olfactory receptors undergo sensory adaptation rapidly
Sense of smell drops by 50% within a second after stimulation

55. LAB: SMELL Pick a partner and spread out
Get a beaker, 4 packs of cotton swabs, and 2 oils.
Follow Directions on lab sheet.
Throw away used cotton swabs. Place beakers and oils back on cart.
Turn in lab on front table.
Pick up a review sheet and begin working on it.

56. Sense of Taste

57. Sense of Taste Taste buds Organs of taste
Located on papillae of tongue, roof of mouth, linings of cheeks and walls of pharynx
Papillae are small peg-like projections on the dorsal surface of the tongue.
Get replaced every 7-10 days

58. Sense of Taste Taste receptors
Taste cells – modified epithelial cells that function as receptors
Taste hairs –microvilli that protrude from taste cells; sensitive parts of taste cells

59. Taste Receptors Papillae Taste buds Epithelium of tongue Taste cell
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Papillae
Taste buds
Epithelium
of tongue
Taste cell
(a)
Taste hair
Supporting
cell
Connective
tissue
Taste
pore
Sensory
nerve fibers
(b)

60. Taste Nerve Pathways
Sensory impulses from taste receptors travel along:
Cranial nerves to…
Medulla oblongata to…
Thalamus to…
Gustatory cortex (for interpretation)

61. Taste Sensations Five primary taste sensations
Sweet – stimulated by carbohydrates
Sour – stimulated by acids
Salty – stimulated by salts
Bitter – stimulated by many organic compounds
Umami- (means delicious in japan) detects beef taste or proteins