senses (eye & ear) & intergumentary system (skin)
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Special Senses
Located within complex sense organs Gustation = sense of taste Olfaction = sense of smell Hearing Equilibrium Vision
The Ear
Used for both hearing and equilibrium
Divided into three parts Outer ear
Pinna (auricle) External auditory canal (meatus)
Contains cerumen (earwax) Tympanic membrane (eardrum)
Transmits sound waves to middle ear
The Ear (con’t)
Middle ear Houses three ossicles
Malleus (hammer) Incus (anvil) Stapes (stirrup)
Soundwaves are transmitted from footplate of stapes
Eustachian tube Connects middle ear to nasopharynx Equalizes pressure between outer and middle ear
The Ear (con’t) Inner ear
Complex labyrinth shape Filled with fluid Contains cochlea
Organ of Corti Vestibular apparatus
Sense of equilibrium Semicircular canals
Vestibulocochlear nerve Cochlear branch transmits hearing impulses Vestibular branch transmits equilibrium impulses
Otitis
Inflammation of the ear Otitis media = infection leading to accumulation
of fluid in middle ear Causes
Obstruction of eustachian tube caused by Spreading infection
Treatment Antibiotics Myringotomy
Otitis (con’t)
Otitis externa Inflammation of external auditory canal Also known as “swimmer’s ear” Caused by:
Fungus Bacterium
Common among: People living in hot climates Swimmers
Meniere Disease
Involves production and circulation of inner ear fluid
Symptoms Vertigo (dizziness) Hearing loss Tinnitus (ringing in ears) Pressure
Treatment Drugs (to treat nausea and dizziness) Severe cases
Inner ear or eighth cranial nerve destroyed surgically
The Eye and Vision
Eye has three layers Sclera
Outermost layer Known as “White of the eye” Extends over front of eye as transparent
cornea
Uvea
Uvea Middle, vascular layer Consists of:
Choroid Ciliary body
Muscle controls shape of lens Allows for accommodation
Iris Muscular ring Controls size of pupil Determines eye color
Retina Innermost layer Actual visual receptor Consists of specialized cells:
Rods Function in dim light Low visual acuity Do not respond to color
Cones Active in bright light High visual acuity Respond to color
Eye Protection
Orbit = bony socket Eyelids
Conjunctiva Thin membrane Covers anterior portion of eye
Eyebrows Eyelashes Tears Lacrimal glands
Bathe eyes with lubricating fluid Fluid drains into nose
Errors of Refraction
Myopia = nearsightedness Eyeball too long Images form in front of retina
Hyperopia = farsightedness Eyeball too short Images form behind retina
Astigmatism = irregularity in curve of cornea or lens
Glasses can correct most of these impairments
Infection
Conjunctivitis = inflammation of conjunctiva Commonly known as “pinkeye” Highly infectious
Trachoma = inflammation of cornea and conjunctiva Results in scarring Common cause of blindness in 3rd world countries
Ophthalmia neonatorum = acute conjunctivitis in newborns Caused by gonorrhea
Disorders of Retina
Retinal detachment Separation of retina from choroid Caused by:
Tumor Hemorrhage Injury to eye
Repaired with laser surgery
Cataract
Opacity of lens caused by: Disease Injury Chemicals Exposure to UV rays
Must be removed to prevent blindness Anterior capsule removed Phacoemulsification
Glaucoma Increased pressure within eyeball More aqueous humor produced than can be
drained away Leads to blindness Many causes Screening at routine eye exams Treatment
Medication Surgery