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membrane that lines the eyelid and attaches to the eye; secretes mucus to lubricate the eye
Inflammation of the conjunctiva results in redden irritated eyes; Pinkeye - viruses and bacteria
produces lacrimal fluid (tears) that contain antibodies and lysozyme; protects, moistens, and lubricates the eye, cold causes the lacrimal mucosa to swell causing watery eyes
Transparent, central anterior portion; allows light to pass through; repairs easily; transplanted without rejection; no blood vessles
Middle layer; blood rich, pigment prevents scattering light; modified internally into two structures - Ciliary Body and Iris
Detailed vision with color; most are in the middle; three types; cones are sensitive to different wavelengths
Biconvex crystal-like structure; focuses light and images onto the retina; held in place by a sespensory ligament attached to the cillary body
Watery fluid between the lens and cornea; similar to blood plasma; maintains pressure; provides nutrients for the lens and cornea; absorbed into the venous blood through the canal of schlemm
Gel-like substance behind the lens; keeps the eye from collapsing; is not replaced and lasts a lifetime
light must be focused on a point on the retina; the eye is set for distance vision (20+feet); lens must change shape to focus close objects
the autonomic nervous system controls the internal muscles of the eye; bright light constricts pupils (radical and ciliary muscles); external muscles control eye movements (convergence)
Nearsightedness; light rays focus in front of the retina; eyeball is too long; lens is too strong; lens is too curved; concave corrective lenses
Farsightedness; light focuses behind the retina; eyeball is too short or a lazy lens; eyestrain; convex corrective lenses
unequal curvatures of the cornea or lens; blurry images because light is in lines not points; require special lenses
External auditory canal
narrow chamber, lined with skin and ceruminous glands ,in the temporal bone; ends at the tympanic membrane; conducts sound vibrations towards the ear drum
Middle ear (tympanic cavity)
air filled cavity in the temporal bone; opening to the auditory canal is covered by the typanic membrane
connects the middle ear to the throat; allows equalizing pressure (yawning/ swallowing/ collapsed)
Bones of the Tympanic Cavity
Malleous, Incus, Stapes; vibrations from the tympanic membrane move the malleus moving the other bones transferring sound to the inner ear
filled with perilymph (plasma like fluid); bony chambers in the temporal bone - Cochlea, Vestibule, Semicircular canals
Organ of Corti
Inside the cochlea; hair cells (hearing receptors); gel like membrane lies over the hair to bend them with vibrations activate; hair stimulation sends impulses to temporal lobe through the cochlear nerve
Maculae - receptors in the vestibule; report on the position fo the head with respect to gravity; keep our heads up; hair cells are in the otolithic membrane (jellylike membrane); otoliths (tiny stones float in gel around the hair); movement causes the otoliths to move the hair cells and send impulses to the brain
Crista ampullaris - receptor region in the semicircular canals that respond to angular or rotary movements of the head; contain tuffs of hair covered in cupula(gelatinous cap); action of angular head movements stimulates the cupula and the hair cells sending impulses through the vestibular nerve to the cerebellum
when there is a degeneration or damage to the receptor cells in the Organ of Corti to the auditory cortex
can still hear with bone conduction; hearing aids; build up of wax or fusion of ossioles
Five taste receptors
salty (metal ions), sweet (sugars, Saccharine, amino acids), bitter (alkaloids) ,sour (acids), umami (meat)
receptors for smell - roof of the nasal cavity; neurons with olfactory hairs (cilia in the nasal epithelium); Chemical are dissolved in mucus; impulses are transmitted through the olfactory nerve to the brain where smell interpretations are made
Sides of papillae; specific receptor cells that respond to chemicals in saliva are called gustatory cells; Gustatory hairs protrude through taste pores; hairs are stimulated by chemicals in saliva
Developmental aspects of the Special Senses
Formed early as an embryo; vision is not fully functioning at birth; eye grow till age 8/9; lenses never stop growing; lacrimal glands don't fully develop till 2 weeks after birth
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