7 Lesson 7.1: The Eye Lesson 7.2: The Ear Lesson 7.3: Smell and Taste The Sensory Systems

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Lesson 7.1: The Eye

Lesson 7.2: The Ear

Lesson 7.3: Smell and Taste

The Sensory Systems

Lesson 7.1

The Eye

Chapter 7: The Sensory Systems

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• Tarsal glands– located in the eyelids– produce an oily secretion

• Ciliary glands- modified sweat glands- located between the eyelashes

• Conjunctiva- membrane that covers the exposed eyeball and lines

the eyelid- secretes a lubricating mucus

External Structures of the Eye


• Lacrimal glands- above the lateral end of each eye- release tears through excretory ducts- tears contain lysozyme, an enzyme that attacks bacteria- tears drain into the lacrimal canaliculi located in the

medial corner of each eye, then to the nasolacrimal duct, then to the nasal cavity



• tarsal glands• ciliary glands


• conjunctiva• lacrimal glands


• 6 extrinsic eye muscles• named by shape and location

– rectus – long muscle fibers– oblique – muscles are at an angle– location – inferior, superior, lateral, medial

Extrinsic Muscles


Extrinsic Muscles


• eyeball is a hollow chamber filled with aqueous and vitreous humor- fluids that help the eyeball maintain shape

• 3 tissue layers form the wall of the eyeball– sclera– choroid– retina

Internal Structures of the Eye


• Sclera- outer layer of the eye- consists of the white part of the eye and the cornea- cornea contains no blood supply

3 Tissue Layers of the Eyeball


• Choroid- middle layer of the eye- contains rich supply of blood vessels- includes the iris

o colored part of eyeo contains 2 sets of muscles which control the amount of light

admitted to the eyesphincter pupillae – contracts in the presence of bright light

or when the eye focuses on an object up close – pupil grows smaller

Dilator pupillae – contracts in the presence of dim light –or when the eye focuses on a distant object – pupil grows larger

- includes the pupil – opening through which light passes into the- the interior of the eye



• Retina- innermost layer of the eye- contains 2 types of light-sensitive sensory neurons

o rods – activated in dim lighto cones – sensitive to bright light and provide color vision

- bipolar neurons provide connections between the retina

and rods and cones



Internal Structures of the Eye


• area on the retina where the optic nerve joins the eye – optic disc

• no rods and cones on the optic disc• we do not perceive this blind spot because the

brain fills in this visual info from the other eye

Blind Spot


• located behind the iris• transparent, flexible structure• held in place by suspensory ligaments which

attach to the ciliary body- ciliary body contracts to view objects within 20 ft which

changes the shape of the lens – after the age of 40, the

ability of the ciliary body to contract diminishes

Lens


• optic nerve - receive impulses from the rods and cones and transmits

the impulses to the brain

• optic chiasm- location in the brain where the optic nerves cross

• optic tracts- nerve fibers exiting the optic chiasm- carry visual stimuli to the occipital lobe

Vision


Vision Disorders


• vision disorders

Vision Disorders

http://www.g-wlearning.com/healthsciences/9781619604124/student/ch07/video01.htm


• Conjunctivitis– also known as pink eye– contagious inflammation of the conjunctiva

• Cataracts- Clouding of the transparent lens of the eye causing

blurred vision, poor night vision, and halos around light

• Glaucoma- increased pressure within the eyeball

• macular degeneration- progressive loss of central vision- peripheral vision remains unaffected

Eye Diseases


• diabetic retinopathy- caused by long-term diabetes- damage to the retina caused by swelling and leaking

of the vessels that supply blood to the retina

- leading cause of blindness in American adults

• vitreous floaters- tiny chunks of the gel-like vitreous humor break off and

float in the aqueous humor

- irregular shaped specks drift within your field of vision

Eye Diseases


Fill in the blanks with: choroid, cornea, cones, or vitreous.

1. The pupil is part of the _______________ tissue layer.

2. The two humors are aqueous and _______________.

3. The retina contains the rods and _______________.

4. The clear part of the sclera is the _______________.

Review and Assessment

Lesson 7.2

The Ear



• external ear– auricle

Irregularly-shaped outer portion of ear– auditory canal

short, tube-like structure connected to the auricle walls are lined with skin that contain ceruminous glands

that produce cerumen (earwax)– tympanic membrane

eardrum soundwaves cause the eardrum to vibrate Separates the outer ear from the middle ear

Anatomy of the Ear


• middle ear (tympanic cavity)– ossicles – smallest bones in the body

• hammer, anvil, stirrup• transmit and amplify sound waves• tympanic membrane attaches to the hammer which

attaches to the anvil which attaches to the stirrup which attaches to the oval membrane

– Eustachian tube• connects the middle ear to the pharynx• equalizes pressure on either side of the tympanic

membrane

Anatomy of the Ear


Anatomy of the Ear


• internal ear- semicircular canals

- bony labyrinth winding tunnels filled with clear fluid called perilymph

- membranous labyrinth inside the bony labyrinth filled with thicker fluid called endolymph

– cochlea• cochlear nerve carries information about hearing

– vestibule • vestibular nerve carries information about balance

- vestibular and cochlear nerves join to form the vestibulocochlear

nerve

Anatomy of the Ear


Inner Ear


• Sound waves enter the ear,– transmitted through the auditory canal - cause the tympanic

membrane to vibrate

• the hammer, anvil, and stirrup transmit and amplify the vibrations to the membrane of the oval window causing the fluid in the inner ear (endolymph) to be set into motion

• cochlear duct - the membranous labyrinth inside the cochlea

• inside the cochlear duct is the organ of Corti which contains hair cells which are specialized hearing receptors

• these hair cells are stimulated by the motion of the endolymph

Hearing


• stimulation of cilia cells stimulates the cochlear branch of the vestibulocochlear nerve

• the cochlear nerve sends the impulse to the auditory region of the brain in the temporal lobe

Hearing


• hair cells in the semicircular canals are stimulated by movement of endolymph in the canals

• vestibular nerve is stimulated and information on body orientation is sent to the cerebellum

Balance/Equilibrium


• Deafness• Tinnitus

- ringing in the ears- hair cells in the organ of Corti are damaged- often caused by repeated exposure to loud noise

• external otitis (swimmer’s ear) - bacterial or fungal infection of the auditory canal caused

by immersion in contaminated water

Disorders and Infections of the Ear


• otitis media (middle ear infection)- caused by bacteria or virus- common in infants and toddlers because their

Eustachian tubes are not fully developed- treated with antibiotics or in chronic cases, tubes are

inserted in the tympanic membrane to relieve pressure

• labyrinthitis (inner ear infection)- often affects the semicircular canals- can cause vertigo (dizzines), nausea, and vomiting

Disorders and Infections of the Ear


True or False?

1. External otitis is swimmer’s ear.

2. The ossicles are in the external ear.

3. Hair cells are responsible for equilibrium.

4. The cochlea is part of the inner ear.

5. Labyrinthitis is an inner ear infection.


Lesson 7.3

Smell and Taste



• olfactory sense (sense of smell)• injuries and disease of the nose• gustatory sense (sense of taste)• disorders of the tongue

Smell and Taste


• olfactory region• olfactory receptor cells• olfactory hairs• olfactory filaments• olfactory nerve• olfactory bulb

Olfactory Sense


Olfactory Sense


• rhinitis– inflammation of nasal membrane

• septum problems– deviated septum

Injuries and Disorders of the Nose


• taste buds• papillae• gustatory cells• gustatory hairs• taste pores• tastants

Gustatory Sense


• infection– severely bitten tongue during a traumatic accident– tongue piercing

• injury• abnormal growth

– hairy tongue– burning mouth syndrome

Disorders of the Tongue


Match these words with 1–4 below: gustatory, gustatory hairs, olfactory hairs, rhinitis.

1. inflammation of the nasal membrane

2. sense of taste

3. part of taste bud

4. part of sense of smell


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7 Lesson 7.1: The Eye Lesson 7.2: The Ear Lesson 7.3: Smell and Taste The Sensory Systems