SPECIAL SENSES EYES, EARS, NOSE 1

The Eyes have it!: Lacrimal glands..produce tears to moisten and cleanse the eye Conjunctiva..mucous membrane that lines eyelids and covers front of eye for extra protection Sclera..”white” of eye,tough connective tissue that maintains shape of eye Cornea..circular,transparent part of the front of the sclera 2

Parts of the Eye 3

Choroid coat..middle layer interlaced with blood vessels that nourish eye Retina..inner most layer of nerve cells which transmits light impulses to optic nerve Iris.. Colored portion of eye located behind cornea Pupil..opening, center of the iris,regulates amount of light entering eye 4

5

Parts of the Eye Lens.. circular structure behind pupil, it refracts(bends) light to focus on retina Aqueous humor..clear watery fluid that fills space between cornea and iris Vitreous humor..jellylike substance that fills area behind lens helps shape eyeball and refracts light 6

Parts of the Eye 7

Diseases & Disorders of the Eye Amblyopia..lazy eye Astigmatism..abnormal shape of eye causing blurred vision Conjuntivitis..pink eye, contagious infection caused by bacteria or virus 8

Diseases & Disorders of the Eye Cataract..cloudy or opaque lens causing blurred vision, halos, and gradual vision loss May result from trauma or aging Treated by surgical removal of lens Symptoms include blurred vision, halos around lights, gradual vision loss, milky- white pupil in later stages 9

Diseases & Disorders of the Eye Glaucoma..increased intraocular pressure caused by excess aqueous humor. Common after age 40 Leading cause of blindness Symptoms include loss of peripheral vision, halos around lights,limited night vision and mild aching 10

Diseases & Disorders of the Eye Hyperopia..farsightedness,image focused behind the retina Myopia..nearsightedness,image focused in front of the retina Presbyopia..farsightedness caused by loss of lens elasticity in the normal aging process (glasses or contacts) Strabismus..eyes do not focus together due to muscle weakness,eyes may cross (eye exercise or surgery) 11

“LEND ME YOUR EARS” The ear is the organ that controls hearing and balance Transmits sound waves to the auditory nerve (vestibulocochlear) Impulses go on to brain for interpretation 12

THE EAR 13

PARTS OF THE EAR Pinna or auricle..outer ear,elastic cartilage covered by skin External Auditory canal..external tube or canal of ear Tympanic membrane..eardrum, membrane that separates outer ear from middle ear,vibrates when sound waves hit it,transmits to middle ear 14

PARTS OF THE MIDDLE EAR Small space or cavity in the temporal bone containing ossicles(3 small bones) which transmit sound waves to inner ear Malleus Incus Stapes Eustachian tube..connect the middle ear to the pharynx(throat)and equalizes pressure on both sides of the eardrum 15

PARTS OF THE INNER EAR Oval window..membrane that separates inner ear from middle ear Vestibule..acts as entrance to inner ear Cochlea..delicate hair-like cells shaped like a snail’s shell,receptor of sound Semicircular canals..contain liquid and delicate hair like cells that bend when liquid moves with head and body movement to maintain balance. 16

DISEASES & DISORDERS Otitis Externa..inflammation of external auditory canal caused by bacterium or virus Caused by swimming in contaminated water Inserting bobby pins, fingernail, and swabs into ear Otitis Media.. Inflammation or infection of middle ear caused by bacterium or virus, freq. follows sore throat Symptoms include pain,vertigo,nausea,vomiting & fluid buildup in middle ear Treatment: myringotomy & insertion of tubes 17

DISEASES & DISORDERS Meniere’s disease..fluid collection with degeneration of the hair cells in the cochlea and vestibules causing vertigo Symptoms severe vertigo, tinnitis, nausea,vomiting, loss of balance, tendency to fall Otosclerosis..immobile stapes with conductive hearing loss 18

DISEASES & DISORDERS Hearing loss Conductive or deafness..sound waves not conducted to inner ear  Wax(cerumen) plug  Foreign body obstruction  Infection  Otosclerosis  Ruptured tympanic membrane 19

DISEASES & DISORDERS Sensory hearing loss occurs when damage to inner ear or auditory nerve Cannot be corrected Cochlear implants may help somewhat 20

THE TONGUE & TASTE Mass of muscle tissue with projections called papillae, where taste buds are 21

THE NOSE & SMELL Nose..organ of smell Impulses from olfactory receptors carried to brain by olfactory nerve More sensitive than taste Can detect over 6,000 different smells Food does not taste good when smell is affected. 22

SKIN & GENERAL SENSES General sense receptors for pressure, heat, cold,touch, and pain located throughout the body in skin & connective tissue Each receptor perceives only one type sense Messages from these receptors allows the body to respond to it’s environment. 23