1H12.01 Explain the Structure of the Eye

L. Sensory System

1H12.01 Explain the structure of the eye. A. Eye 1. 1” in diameter 2. Protected by orbital cavity, eyebrows, eyelashes, eyelids 3. Lacrimal glands – tears empty into nasal cavity 4. Conjunctiva – thin membrane lines eyelids 5. Wall of eye made up of three coats B. Sclera 1. Outer layer 2. White of the eye 3. Tough coating, helps maintain shape of eye 4. Muscles responsible for moving eye attached to sclera = extrinsic muscles C. Cornea 1. Front of sclera (clear part) no blood vessels 2. Transparent so light rays can pass through D. Choroid coat 1. Middle layer, contains blood vessels 2. Opening in front is pupil 3. Colored, muscular layer surrounding pupil is iris 4. Intrinsic muscles – change size of iris to control amount of light entering through pupil E. Lens 1. Crystalline structure located behind iris and pupil 2. Elastic, disc-shaped, biconvex 3. Situated between the anterior and posterior chambers F. Anterior Chamber – filled with aqueous humor G. Posterior Chamber – filled with vitreous humor H. Retina 1. Innermost layer 2. Light rays focus image on retina 3. Image travels to the cerebral cortex via optic nerve 4. Rods – sensitive to dim light 5. Cones – sensitive to bright light and color 6. Optic disc – on retina, known as blind spot, nerve fibers that form optic nerve

1H12.02 Analyze the function of the eye. A. Eye 1. Protected by orbit, eyebrows, eyelashes, eyelids 2. Lacrimal glands – tears empty into nasal cavity and clean the eyes 3. Conjunctiva – secretes mucous to lubricate eyes B. Sclera 1. Tough coating, helps maintain shape of eye 2. Extrinsic muscles - responsible for moving eye attached to sclera C. Cornea - Transparent so light rays can pass through

Summer 2005 L.1 D. Choroid coat 1. Middle layer, contains blood vessels 2. Intrinsic muscles – change size of iris to control amount of light entering through pupil 3. Pupil constricts – gets smaller – in bright light 4. Pupil dilates – gets larger – in dark light E. Lens 1. Where light rays are refracted 2. Accommodation – change in the shape of the lens to allow for near and distant vision F. Retina 1. Light rays focus image on retina 2. Image travels to the cerebral cortex via optic nerve 3. Rods – sensitive to dim light 4. Cones – sensitive to bright light and color 5. Optic disc – on retina, known as blind spot, nerve fibers that form optic nerve G. Pathway of vision - Image travels through cornea, then pupil, through lens, hits retina, picked up by rods and cones and carried to optic nerve where the brain interprets image

1H12.03 Explain the structure and function of the ear, nose, and tongue. A. Outer ear 1. Pinna (auricle) a. Visible ear b. Collects sound waves 2. External auditory canal – ear canal 3. Cerumen – ear wax, protects the ear 4. Tympanic membrane – ear drum, separates outer and middle ear B. Middle ear 1. Cavity in temporal bone 2. Connects with pharynx by Eustachian tube - which equalizes pressure in the middle ear with outside atmosphere 3. Bones - transmit sound waves from ear drum to inner ear a. Malleus (hammer) b. Incus (anvil) c. Stapes (stirrup) C. Inner ear 1. Cochlea - spiral shaped organ of hearing, contains a membranous tube, the cochlear duct – which is filled with fluid that vibrates when sound waves are transmitted by the stapes 2. 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 3. Semicircular canals – three structures in inner ear that contain liquid set in motion by head and body movements 4. Impulses sent to cerebellum to help maintain body balance (equilibrium) D. Pathway of hearing – ear to external auditory canal to tympanic membrane to ossicles (malleus, incus and stapes) to cochlea to auditory nerve to brain E. Nose 1. Smell accounts for 90% of taste 2. Tissue in the nose, olfactory epithelium, contains specialized nerve cell receptors 3. Those receptors stimulate the olfactory nerve to the brain

Summer 2005 L.2 F. Tongue 1. Mass of muscle tissue 2. Bumps on surface are papillae, they contain taste buds 3. Receptors in taste buds send stimuli through 3 cranial nerves to cerebral cortex

1H12.04 Discuss characteristics and treatment of common sensory disorders. A. Disorders of the eye 1. Conjunctivitis (Pink eye) a. Inflammation of conjunctival membranes in front of eye b. Redness, pain, swelling and discharge c. Highly contagious d. Rx – antibiotic eye drops 2. Glaucoma a. Excessive intraocular pressure causing destruction of the retina and atrophy of the optic nerve b. Caused by the overproduction of aqueous humor, lack of drainage, or aging c. Symps – develop gradually, mild aching, loss of peripheral vision, halo around light d. Tonometer – measures intraocular pressure e. Rx – drugs or laser surgery 3. Cataracts a. Lens of eye gradually becomes cloudy b. Frequently occurs in people over 70 c. Causes painful, gradual blurring and loss of vision d. Rx – surgical removal of the lens 4. Sty (hordeolum) a. Abscess at the base of an eyelash in sebaceous gland b, Symps – red, painful, swollen c. Rx – warm, wet compresses 5. Eye injury - Glass or fragment in eye – cover eye and seek medical help, do not remove the object 6. Color blindness a. Cones affected b. Genetic disorder that is carried by female and transmitted to males B. Vision defects 1. Presbyopia a. Lens loses elasticity, can’t focus on close or distant objects b. Usually after age 40 c. Rx – bifocals 2. Hyperopia a. Farsighted b. Focal point beyond retina, eyeball too short c. Convex lenses help 3. Myopia a. Nearsighted b. Eyeball too long c. Concave lenses help 4. Astigmatism a.. Irregular curvature of the cornea or lens, causing blurred vision or eye strain b. Rx – corrective lenses

Summer 2005 L.3 5. Diplopia – double vision 6. Strabismus (cross-eyed) a. Eye muscles to not coordinate their actions b. Usually in children c. Rx – eye exercises or surgery 7. Ophthalmoscope – instrument for viewing inside the eye 8. Snellen eye chart – chart that uses letters or symbols in calibrated heights to check for vision defects C. Disorders of the ear 1. Hearing loss a. Hearing is fragile, loud noise over period of time can cause hearing loss b. Symps – tinnitus (ringing in ears) and difficulty understanding what people are saying 2. Otitis Media a. Infection of middle ear b. Often complication of common cold in children c. Rx – antibiotics d. Myringotomy – tubes inserted through tympanic membrane to relieve pressure 3. Otosclerosis a. Chronic , progressive middle ear disorder b. Stapes becomes spongy and then hardens, becoming fixed and immobile c. Rx – stapedectomy and total replacement of stapes 4. Tinnitus – ringing of ears from impacted wax, otitis media, loud noise, etc. 5. Types of hearing loss a. Conductive – sounds prevented from reaching inner ear b. Sensorineural – problem with inner ear and auditory nerve D. Disorders of the nose 1. Rhinitis a. Inflammation of lining of nose with congestion, drainage b. Cause – allergies, drugs, infection, odors, etc. c. Rx – eliminate cause, antihistamine

Summer 2005 L.4 Unit L: Sensory System Terminology List

Eye Ear

1. accommodation 1. auricle 2. anterior chamber 2. cerumen 3. aqueous humor 3. cochlea 4. choroid coat 4. Eustachian tube 5. cones 5. external auditory canal 6. conjunctiva 6. incus 7. constrict 7. malleus 8. cornea 8. organ of Corti 9. dilate 9. pathway of hearing 10. extrinsic muscles 10. pinna 11. intrinsic muscles 11. semicircular canals 12. iris 12. stapes 13. lacrimal glands 13. tympanic membrane 14. lens 15. optic disc 16. optic nerve Nose/Tongue 17. orbital cavity 18. posterior chamber 1. olfactory nerve 19. pupil 2. papillae 20. retina 3. taste buds 21. rods 22. sclera 23. vitreous humor

Disorders and Related Terminology

1. astigmatism 15. rhinitis 2. cataracts 16. sensorineural hearing loss 3. color blindness 17. Snellen eye chart 4. conductive hearing loss 18. sty 5. conjunctivitis 19. vertigo 6. deafness 7. epistaxis 8. glaucoma 9. hordeolum 10. hyperopia 11. myopia 12. ophthalmoscope 13. otitis media 14. presbyopia

Summer 2005 L.5 The Eye . 1” in diameter . Protected by orbital socket of skull, eyebrows, eyelashes and eyelids . Bathed in fluid from LACRIMAL GLANDS – tears empty into nasal cavity . CONJUNCTIVA – thin membrane that lines the eyelids and covers part of the eye, secretes mucous to lubricate eye . Wall of the eye made up of three coats

SCLERA . Outer layer . White of the eye . Tough coating, helps maintain shape of eye and protects what’s inside . Muscles responsible for moving the eye are attached to the sclera – called EXTRINSIC MUSCLES

Summer 2005 L.6 CORNEA . Front of sclera – clear part (no blood vessels) . Transparent so light rays can pass through

. Gets O2 and nutrients through lymph

CHOROID COAT . Middle layer . Contains blood vessels . Opening in front is the PUPIL . Colored, muscular layer surrounding pupil is IRIS

Summer 2005 L.7 . INTRINSIC MUSCLES – change size of iris to control amount of light entering through the pupil LENS . Crystalline structure located behind iris and pupil . Elastic, disc-shaped, biconvex . Situated between the anterior and posterior chambers . ACCOMMODATION – change in the shape of the lens to allow for near and distant vision . ANTERIOR CHAMBER filled with AQUEOUS HUMOR, a watery fluid. . POSTERIOR CHAMBER filled with transparent, jellylike substance – VITREOUS HUMOR

RETINA . Innermost layer . Light rays focus an image on the retina . The image travels to the cerebral cortex via the OPTIC NERVE

Summer 2005 L.8 . If light rays don’t focus properly on the retina, corrective lenses can bend the light rays as required. . Retina contains specialized cells – rods and cones . RODS – sensitive to dim light . CONES – sensitive to bright light and color . OPTIC DISC – on the retina, known as the blind spot – nerve fibers gather here to form the optic nerve, no rods or cones

Pathway of Vision

Cornea

Pupil Lens (Where light rays are refracted)

Rods and Cones Retina (pick up stimulus) RR

Summer 2005 L.9 Optic Nerve RR The Ear

Hearing and equilibrium 3 parts: Outer, middle and inner ear

Outer Ear PINNA (AURICLE) – outer ear, collects sound waves EXTERNAL AUDITORY CANAL – ear canal CERUMEN – earwax, protects the ear TYMPANIC MEMBRANE – ear drum, separates outer and middle ear

Summer 2005 L.10 Middle Ear . Cavity in temporal bone . Connects with pharynx by EUSTACHIAN TUBE – which equalizes pressure in the middle ear with outside atmosphere . Bones in middle ear that transmit sound waves from ear drum to inner ear 1.MALLEUS (hammer) 2.INCUS (anvil) 3.STAPES (stirrup)

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  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

Summer 2005 L.11 cerebellum to help maintain body balance (equilibrium).

Pathway of Hearing

External Tympanic Auditory Canal Membrane

Ossicles (malleus, Cochlea incus & stapes) RR

Auditory nerve

Summer 2005 L.12 The Nose  Smell accounts for 90% of taste  Tissue in the nose, olfactory epithelium, contains specialized nerve cell receptors.  Those receptors stimulate the OLFACTORY NERVE to the brain.

The Tongue

 Mass of muscle tissue  Bumps on the surface are PAPILLAE, they contain the TASTE BUDS  Receptors in taste buds send stimuli through 3 cranial nerves to the cerebral cortex

Summer 2005 L.13 Disorders of the Eye

CONJUCTIVITIS . Pink eye . Inflammation of conjunctival membranes in front of the eye . Redness, pain, swelling and discharge . Highly contagious . Rx – antibiotic eye drops

GLAUCOMA . Excessive intraocular pressure causing destruction of the retina and atrophy of the optic nerve . Caused by overproduction of aqueous humor, lack of drainage, or aging . Symps – develop gradually – mild aching, loss of peripheral vision, halo around the light . TONOMETER – measures intraocular pressure . Rx – drugs or laser surgery

Summer 2005 L.14 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

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

Vision Defects

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

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

Summer 2005 L.15 MYOPIA . Nearsighted . Eyeball too long . Concave lenses help

ASTIGMATISM . Irregular curvature of the cornea or lens, causing blurred vision and eye strain . Rx – corrective lenses

OPHTHALMOSCOPE – instrument for viewing inside the eye

SNELLEN EYE CHART – chart that uses letters or symbols in calibrated heights to check for vision defects

Summer 2005 L.16 Disorders of the Ear Loud noise and hearing loss – hearing is fragile. Loud noise over a period of time can cause hearing loss. (Deafness)

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

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

Summer 2005 L.17