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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
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• 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
External Structures of the Eye
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• tarsal glands• ciliary glands
External Structures of the Eye
• conjunctiva• lacrimal glands
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• 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
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Extrinsic Muscles
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• 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
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• 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
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• 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
3 Tissue Layers of the Eyeball
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• 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
3 Tissue Layers of the Eyeball
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Internal Structures of the Eye
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• 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
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• 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
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• 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
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Vision Disorders
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• vision disorders
Vision Disorders
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• 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
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• 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
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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
Chapter 7: The Sensory Systems
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• 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
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• 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
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Anatomy of the Ear
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• 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
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Inner Ear
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• 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
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• 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
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• 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
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• 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
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• 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
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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.
Review and Assessment
Lesson 7.3
Smell and Taste
Chapter 7: The Sensory Systems
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• olfactory sense (sense of smell)• injuries and disease of the nose• gustatory sense (sense of taste)• disorders of the tongue
Smell and Taste
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• olfactory region• olfactory receptor cells• olfactory hairs• olfactory filaments• olfactory nerve• olfactory bulb
Olfactory Sense
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Olfactory Sense
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• rhinitis– inflammation of nasal membrane
• septum problems– deviated septum
Injuries and Disorders of the Nose
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• taste buds• papillae• gustatory cells• gustatory hairs• taste pores• tastants
Gustatory Sense
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• infection– severely bitten tongue during a traumatic accident– tongue piercing
• injury• abnormal growth
– hairy tongue– burning mouth syndrome
Disorders of the Tongue
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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
Review and Assessment
