1. Sensory System Unit-L

2. Main Objectives Describe the structure of the eye
Analyze the function of the eye
Describe the structure of the ear, nose, and tongue.
Analyze the function of the ear, nose, and tongue.
Analyze characteristics and treatment of common sensory disorders.

3. The Eye
1” in diameter
Protected by orbital cavity of skull, eyebrows, eyelashes and eyelids.
Bathed in fluid from Lacrimal Glands ( tears empty into nasal cavity)

4. Cornea – Front of sclera
Clear structure called “window of the eye” (no blood vessels)
Transparent so light rays can pass through
Gets O2 and nutrients through lymph

5. Conjunctiva
A thin membrane that lines the eyelids and covers part of the eye.
It secretes mucous to lubricate the eye.

6. Wall of Eye is made up of 3 coats
Sclera, Choroid Coat, and the Retina
SCLERA- Outer layer
White of the eye
Tough, fibrous capsule helps maintain shape of eye and protects the structure within. .

7. EXTRINSIC MUSCLES
Muscle responsible for moving the eye that are attached to the sclera.

8. Choroid Coat Middle coat Contains blood vessels
Circular opening in front is the PUPIL
Colored, muscular layer surrounding pupil is IRIS

9. PUPILS Pupil constricts-gets smaller-in bright light
Pupil dilates-gets larger-in dark light

10. INTRINSIC MUSCLES Theses muscles change size of iris
& pupil to control
amount of light
entering the eye.
The black center is
a hole called the pupil.

11. LENS Crystalline structure located behind iris and pupil.
Elastic, disc-shaped, biconvex
Situated between the anterior and posterior chambers.
The part of the eye that is removed during cataract surgery.
Lies directly behind the pupil.

12. LENS
Accommodation is the function of the lens. It adjusts the focus of an eye to give clear vision

13. ANTERIOR CHAMBER filled with AQUEOUS HUMOR, a watery fluid.
POSTERIOR CHAMBER filled with transparent, jellylike substance- VITREOUS HUMOR

14. Retina Innermost layer Light rays focus an image on the retina
The optic nerve is formed on the optic disc by nerve fibers.
The image travels to the cerebral cortex via the OPTIC NERVE.

15. RODS & CONES Retina contains specialized cells- rods and cones.
RODS- sensitive to dim light.
CONES- sensitive to bright light and color.

16. Blind Spot
OPTIC DISC- on the retina, known as the blind spot- nerve fibers gather here to form the optic nerve, no rods or cones.

18. The Pathway of Vision CORNEA PUPIL LENS (Light rays are refracted)
RETINA

19. The Ear Outer Ear PINNA (AURICLE)- outer ear, collects sound waves
EXTERNAL AUDITORY CANAL- ear canal
TYMPANIC MEMBRANE- ear drum, separates outer and middle ear.

20. CERUMEN- earwax, gives protection to the ear

21. Cavity in temporal bone Tube that connects middle ear
The Ear
Middle Ear
Cavity in temporal bone
Tube that connects middle ear
& (throat)
pharynx by EUSTACHIAN
TUBE- which equalizes
pressure in the middle ear
with outside atmosphere.

22. The Ear
Bones in middle ear transmits sound waves from ear drum to inner ear.
MALLEUS (hammer)
INCUS (anvil)
STAPES (stirrup)

23. The Ear Inner Ear Contains spiral shaped organ of hearing- the COCHLEA
The cochlea contains a membranous tube, the cochlear duct- which is filled with fluid that vibrates when sound waves are transmitted by the stapes.
The organ of Corti is located within the Cochlea.

24. The Ear
ORGAN OF CORTI- delicate hairlike cells that pick up vibrations of fluid and transmit them as a sensory impulse along the auditory nerve to the brain.
SEMICIRCULAR CANALS- three structures in the inner ear, contain liquid that is set in motion by head and body movements- impulses sent to cerebellum to help maintain body balance (equilibrium).

26. The Ear Pathway of Hearing
Sound waves Pinna External Auditory Canal Tympanic Membrane Ossicles ( malleus, incus, & stapes) Cochea Auditory nerve Brain

27. Tongue Mass of muscle tissue
The projections on the surface of the tongue, that contain TASTE BUDS are called papillae.
Receptors in the taste buds send stimuli through 3 cranial nerves to the cerebral cortex.

28. The Nose Smell accounts for 90% of taste
Tissue in the nose, olfactory epithelium, contains specialized nerve cell receptors.
Those receptors in the nose stimulate the OLFACTORY NERVE to the brain.

29. Common Disorders of the Eye
CONJUCTIVITIS
Pink eye
Inflammation of conjunctival membranes in front of the eye.
Redness, pain, swelling, and discharge
Highly contagious
Should not be sharing towels.
Rx- antibiotic eye drops

30. Tube in the Ear

31. Common Disorders of the Eye
Glaucoma
Excessive intraocular pressure causing destruction of the retina and atrophy of the optic nerve
Caused by over production of aqueous humor, lack of drainage, or aging.

32. Common Disorders of the Eye
Symptoms- develop gradually – mild aching, loss of peripheral vision, halo around the light.
TONOMETER- measures intraocular pressure
Rx – drugs or laser surgery to lower intraocular pressure.

33. Common Disorders of the Eye
CATARACTS
Lens of eye gradually becomes cloudy
Frequently occurs in people over 70
Causes a painful, gradual blurring and loss of vision
Pupil turns from black to milky white
Rx- surgical removal of the lens

34. Common Disorders of the Eye
STY ( HORDEOLUM)
Abscess at the base of an eyelash (in sebaceous gland)
Symps- red, painful and swollen
Rx- warm, wet compresses

35. Eye Injuries
Tears are effective in cleaning the eye, produced by Lacrimal glands.
If glass or fragments get in eye, cover both eyes and see medical treatment. (DO NOT remove the object)
Color blindness- cones are affected – genetic disorder that carried by the female and transmitted to males.

36. Occluder
Used by ophthalmologists to test visual acuity.

37. Color Blindness Cones affected
Genetic disorder that is carried by female & transmitted to males

38. Vision Defects
MYOPIA
nearsighted
Eyeball too long
Concave lenses help

39. Vision Defects HYPEROPIA Farsighted
Focal point beyond the retina because eyeball too short
Convex lenses help

40. Vision Defects PRESBYOPIA
Lens loses elasticity, can’t focus on close or distant objects
Usually occurs after age 40
Rx- bifocals

41. Vision Defects ASTIGMATISM
Irregular curvature of the cornea or lens, causing blurred vision and eye strain
Rx- corrective lenses

42. Vision Defects
AMBLYOPIA
(Lazy Eye)
Reduction or dimness of vision

43. Vision Defects STABISMUS ( cross-eyes)
Eye muscles do not coordinate their actions
Usually in children
Rx – eye exercises or surgery

44. Vision Defects
DIPLOPIA-
double vision

45. Vision Defects OPTHALMOSCOPE- instrument for viewing inside the eye.
SNELLEN EYE CHART- chart that uses letter or symbols in calibrated heights to check for vision defects.

46. Disorders of the Ear Healthy Infected Ear Ear OTITIS MEDIA
Infection of the middle ear
Often a complication of a common cold in children
Rx- antibiotics
If chronic or if fluid builds up- MYRINGOTOMY (opening in the tympanic membrane) with tubes inserted will relieve the pressure.
Healthy Infected Ear Ear

47. Disorders of the Ear
Hearing Loss - hearing is fragile, loud noise over a period of time can cause hearing loss.
Symptoms- TINNITUS (ringing in ears) and difficulty understanding what people are saying

48. Disorders of the Ear
PRESBYCUSIS- deafness due to the aging process, can be helped with the use of hearing aids.

49. Disorders of the Ear OTOSCLEROSIS
Chronic, progressive middle ear disorder
Stapes becomes spongy and then hardens, becoming fixed and immobile
Common cause of deafness in young adults
Rx-stapedectomy and total replacement of stapes

50. Disorders of the Ear
TINNITUS - ringing in the ears from impacted wax, otitis media, otosclerosis, loud noise, blockage of normal blood supply to the cochlea, drugs (salicylates)
Types of hearing loss:
Conductive- which sounds are prevented from reaching inner ear
Sensorineural- problems with inner ear or auditory nerve.

51. Disorders of the Nose DEVIATED SEPTUM
Bend in cartilage of nasal septum
Causes breathing problems headaches, snoring, and nose bleeds
Rx- surgical correction
Temporary Rx- Breath Right nasal strips

52. Disorders of the Nose RHINITIS
Inflammation of the lining of the nose with nasal congestion, drainage, sneezing and itching.
Caused by allergies, infection, fumes, odors, emotion, or drugs
Rx- eliminate causes, antihistamines

53. NOW, SEE, THAT WAS NOT TOO BAD!