Definitions Pinna— Elastic cartilage

Tympanic membrane— eardrum

Ear ossicles— malleous, incus, stapes

Two membranes in inner ear— oval window, round window

Eustachian tube— connects ear to throatFunction— equalize pressure

Inner Ear Labyrinth Bony

Cochlea: Hearing Vestibule: Balance Semicircular canals:

Balance Membranous

Lymphs Endolymph

In membranous labyrinth

Perilymph Space between

membranous and bony labyrinth

Hearing

Organ of hearing:

How we hear—happens within the cochlea

Effect of Sound Waves on Cochlear Structures

Hearing Process

Waves move perilymph Perilymph moves vestibular membrane

that moves endolymph Endolymph moves tectorial membrane

which moves the hair cells Hair cells send impulse to nerves & the

brain Sound waves leave through round

window

Auditory Function

Vibrations produce sound waves Volume or loudness : number of hairs

stimulated Pitch: Function of wave frequency

Balance

Static Evaluates position

of head relative to gravity

Detects linear acceleration and deceleration

Kinetic Evaluates

movements of head 3 semicircular

canals Ampulla

endolymph moves when head moves

Semicircular Canals

Contain fluid and hair Movement moves fluid & hairs Sends impulse to brain

Ear Disorders Tinnitus

Ringing, clicking, whistling in ear due to disorders in middle or inner ear

Motion sickness Dysfunctions caused by stimulation of semicircular

canals during motion

Otitis Media Infections in the middle ear

Earache Results from otitis media, dental abscesses, TMJ

pain

The Eye

Structure of the Eye Layers and coats Fibrous Tunic: Outer

Sclera—tough, white, outer portion; maintains shape,protects internal structures, provides muscle

attachment point; continuous with cornea

Cornea—transparent portion of anterior eye; avascular; bends & refracts light

Vascular Tunic: MiddleChoroid—middle layer; blood vessels & darkly

pigmented Ciliary body—holds ciliary muscles (smooth) attached to

lens w/ suspensory ligaments to control lens shape Lens- transparent; bioconvex

Iris—colored, smooth muscle ring with the pupil in the middle; controls light entering pupil

Structure of the Eye Continued

Retina—Inner Retina-incomplete,

innermost layer; nervous layer (contains neurons sensitive to light) Rods (black & white) Cones (color) Fovea Centralis/Macula

lutea- where light is focused; see fine images (area of greatest acuity)

Optic disc (no photoreceptor cells) AKA Blind Spot

Cavities (compartments) in the Eye

Anterior cavity—between the lens and cornea Filled with aqueous humor—clear, watery fluid Helps maintain intraocular pressure Glaucoma—too much intraocular pressure due to

too much aqueous humor

Posterior cavity—behind the lens and posterior portion of the eye Filled with vitreous humor—soft, gelatin-like

substance Helps with intraocular pressure to prevent collapse

Muscles of the Eye

Extrinsic eye muscle—skeletal muscles that move the eyeball

Intrinsic eye muscle—smooth muscles in the eye—involuntary Iris Ciliary body

Accessory structures

Eyebrows & eyelashes—keep some foreign particles out of eye

Eyelids—help with lubricationConjunctiva-mucus membrane lining the lid

(AKA Pink eye (conjunctivitis); caused by an infection or irritation

Closes from outside to in/ top to bottom

Lacrimal Apparatus Lacrimal apparatus

Lacrimal Gland: Produces tears to moisten, lubricate, wash

Lacrimal Canaliculi Collects excess tears

Punctum

Lacrimal Sac

Nasolacrimal duct Opens into nasal cavity

Concept Review

1. What are the 3 main layers of the eye?-sclera, choroid, retina

2. What are the 3 accessory structures and describe their function?

-eyebrows, eyelashes, & eyelids (protection & lubrication)

3. Where are tears formed and where do they go?

-lacrimal gland, nasalacrimal duct

How we see (4 main steps)Formation of Vision on the Retina

1. Refraction of light rays cornea, aqueous humor, lens, vitreous humor

2. Accommodation of lens Increase in curvature to achieve greater refraction

on near objects Emmetropia: Normal resting condition of lens Far vision: 20 feet or more from eye Near Vision: Closer than 20 feet

3. Constriction of pupil Iris contracts to limit the amount of light that

enters the eye

How we see Continued…Formation of Vision on the Retina

4. Convergence of eyesLight must hit the same spot of the retina

on both eyes to see only one objectBoth eyes are directed on the object at the

same angle

Single binocular vision —seeing one object with two eyes

Eye Disorders Myopia: Nearsightedness

Focal point too near lens, image focused in front of retina

Hyperopia: Farsightedness Image focused behind

retina

Presbyopia Degeneration of

accommodation, corrected by reading glasses

Astigmatism: Cornea or lens not uniformly curved

Strabismus: Lack of parallelism of light paths through eyes

Retinal detachment Can result in complete

blindness

Glaucoma Increased intraocular

pressure by aqueous humor buildup

Cataract Clouding of lens

Macular degeneration Common in older people,

loss in acute vision

Diabetes Dysfunction of peripheral

circulation

The Mouth

Sense of Taste

Specific sense organ– TASTE BUDS

Located on projections of tongue called papillae

Structure of a Taste Bud

Gustatory cell—contain tiny, cilia-like gustatory hairs

Taste pore—opening in the papillae that is bathed in saliva

*The chemicals of food must dissolve in the saliva to stimulate the hairs to start an impulse.*

Primary Tastes

The Nose

Sense of Smell

Olfactory organs Sensory hairs Olfactory cells Olfactory nerves Olfactory bulb Olfactory tract

Smelling

Substance must be:Able to become a gasWater soluble or very smallLipid soluble (to get into membrane)

Effects of Aging on the Special Senses

Slight loss in ability to detect odors

Decreased sense of taste

Lenses of eyes lose flexibility

Development of cataracts, macular degeneration, glaucoma, diabetic retinopathy

Decline in visual acuity and color perception