1. Anatomy and Physiology
Special Senses
Anatomy and Physiology

2. Introduction Senses are classified in two major groups:
A. Special – senses of smell, taste, sight, hearing, and balance
B. General – touch, pressure, pain, temperature, itch, and proprioception (position of the body and its various parts)

3. Anatomy of the Eye Medial canthus Lateral canthus
Adult eye is sphere – 1 inch in diameter
Accessory structures: extrinsic eye muscles, eyelids, conjunctiva, lacrimal apparatus
Eyes protected by eyelids
Corners are:
Medial canthus
Lateral canthus

4. Anatomy of the Eye Cont.
Meibomian glands – sebacious glands produce oily secretions - lubricates eye
Ciliary gland – modified sweat gland- between eyelashes
Conjunctiva – membrane - lines eyelid; covers part of outer surface
Conjunctivitis –red eyes, irritation, Pink eye –bacteria or virus – highly contagious

5. Anatomy of the Eye

6. Anatomy of the Eye Cont.
Lacrimal apparatus – gland and ducts drain lacrimal secretions into nasal cavity
Lacrimal glands –Tears flush eyeball
Lysozyme – enzyme that destroys bacteria

7. Internal Structure of Eye
Eye is hollow sphere
wall composed of three tunics or coats
Interior filled with fluid called humors – maintains shape of eye

8. Tunics of Eyes 1. Sclera – outermost tunic – protection – white of eye
A. cornea – transparent – light enters
–no blood vessels
-can be transplanted
–not a tunic

9. Tunics of the Eye cont.
2. Choroid – middle tunic – blood rich and dark pigment
A. Ciliary body – smooth muscle structure
– lens and iris are attached
B. Iris – pigmented portion – eye color
-has muscles to regulate light.
C. Pupil - in iris – light passes

10. Pupil
Close Vision and Bright light – circular muscles contract and pupil constricts allowing less light in
Distant Vision and Dim light – radial fibers contract enlarges pupil (dilate) allows more light in

11. Tunics of the Eye Cont.
3. Retina – innermost tunic – contains millions of receptor cells –rods and cones
Rods and cones -photoreceptors
– nerve impulses transmitted to optic nerve
Rods - see gray and peripheral vision
Cones - allows us to see color
no rods or cones on optic nerve where it leaves the eye –called blind spot or optic disk

12. Inside View
When a doctor looks at the back of your eye, here's the view:

13. Visual problems
Night blindness – vit A deficiency – deteriorates neural retina – rods
Color blindness – lacks one or more cones – common red-green – sex linked trait – found on X chromosomes – most always in males

14. Cont.
Cataracts – vision is hazy – cause blindness – surgically remove lens
Glaucoma – pressure within eye – build up of aqueous humor – causes pain, blindness in older people
Myopia – nearsightedness – distant objects blurry – eyeball too long
Emmetropia – good vision
Hyperopia – farsightedness – eyeball too short – distant objects are clear - p. 283

15. Eye Muscles Lateral rectus - moves eye laterally
Six muscles control the movements of eye.
Lateral rectus - moves eye laterally
Medial rectus - moves eye medially
Superior rectus - elevates eye
Inferior rectus - depresses eye
Inferior oblique - rotates eye
Superior oblique - rotates eye

16. Ch. 8 Day 2

17. The Ear – External Ear Auricle – fleshy part-external ear
Auricle opens into external auditory meatus –leads to eardrum
Auricle directs sound waves toward external auditory meatus

18. External Ear Cont.
Meatus lined with hairs and ceruminous glands – EAR WAX
Eardrum – called tympanic membrane – thin membrane, separates external from middle ear. Sound waves cause eardrum to vibrate.

19. Middle Ear The middle ear contains three auditory ossicles – ear bones
Malleus – hammer
Incus – anvil
Stapes – stirrup
Eustachian tube – enables equalization of air pressure b/w outside and middle ear cavity. Changing altitude causes pain.
swallow, yawn, chew, or hold nose to force air out of lungs

20. Inner Ear
Tunnels called bony labyrinth – maze – has fluid called perilymph
Inner ear has three parts
Cochlea – hearing
Vestibule – between Cochlea & Semicircular canal
Semicircular Canal- balance

21. Steps involved in Hearing – Test Question
Sound waves collected by auricle and conducted through external auditory meatus to tympanic membrane, causing vibrations
Vibrating tympanic membrane causes malleus, incus, and stapes to vibrate

22. Steps involved in hearing Cont.
Vibration of stapes produces vibration in perilymph of scala vestibuli
Causes vibration in cochlea
Vibration detected by hair cells which induce action potential in cochlear neurons
Action potentials conducted to CNS
Perceived as SOUND by cerebral cortex

23. Day 3 Taste and Smell

24. Taste and Smell Chemoreceptors –taste and olfaction(smell)
Taste buds – 10,000 on tongue – few on soft palate and cheeks
Papillae – peglike– where taste buds are on tongue
Four basic types – sweet, sour, bitter, salty
Factors that affect taste – olfactory– congestion – temperature - texture

25. The Tongue Dorsal surface covered with small projections, or papillae.
4 types of papillae:
Fungiform
Filiform
Circumvallate
Foliate

26. FYI Older adults often prefer highly seasoned foods. (Why??)
Mid-40s – diminished ability to taste and smell (fewer receptor cells)
Half of people over 80 have poor taste and cannot smell at all.

27. Geographic Tongue Some papillae fall off Sometimes painful
Map-like, geographic appearance
Only symptom in most cases
Sometimes painful
Sensitivity to hot and spicy foods
No cure – heals by itself
No known cause
Can happen to anyone!

28. Geographic tongue

29. Taste Buds Sweet – tip Salty – anterior sides Sour – posterior sides
Bitter – back
BUT…

30. Taste Buds Cont.
Only slight differences in locations of taste receptors.
Most taste buds respond to two or more types of taste.