Presentation on theme: "Essentials of Pathophysiology"— Presentation transcript:
1 Essentials of Pathophysiology Chapter 38 Disorders of Special Sensory Function: Vision, Hearing, and Vestibular Function
2 Pre lecture quiz (true/false) Conjunctivitis, or inflammation of the conjunctiva, can be caused only by viral organisms.The eustachian tube is lined with a mucous membrane that is continuous with the nasopharynx, and provides a passageway for pathogens to enter the middle ear.Ringing of the ears is known as tinnitus.Many drugs are labeled as ototoxic, or damaging to inner ear structures.Hearing impairment may have a detrimental effect on language development in children.FT
3 Pre lecture quiz_____________, a group of conditions that feature an optic neuropathy, is usually associated with an increase in intraocular pressure.______________ is a disorder of refraction that allows an individual to see objects at close distances without problems, but distant objects are blurred.A lens opacity that interferes with the transmission of light to the retina is known as _______________.______________ media refers to inflammation of the middle ear, usually associated with an acute infection or an accumulation of fluid.An illusion of motion, often described as a sensation of spinning or tumbling, is a disorder of vestibular function known as ________________.CataractsGlaucomaMyopiaOtitisvertigo
4 Eye Anatomy Discussion List the structures light must pass through on its way from the outside to the retinaWhat part does each structure play in vision?
5 Disorders Affecting the Anterior Chamber ConjunctivitisCorneal abrasionCorneal edemaKeratitisGlaucomaOpen-angleAngle-closure
6 ScenarioB. is a 13-year-old girl who is involved in youth recreation programs at the community center where you volunteerShe complains of eye irritationThe left eye is reddened and watery, with some crusting on the eyelashesQuestion:What possible disorders will you consider?
7 Aqueous Humor Aqueous humor is formed by the ciliary body It then flows between the iris and the lens to enter the anterior chamberIn the anterior chamber, it delivers food and oxygen to the lens and corneaThen it drains into tubules of the trabecular meshworkThey empty into the canal of Schlemm
8 The area where the iris meets the cornea It contains the: Iridocorneal AngleThe area where the iris meets the corneaIt contains the:Trabecular meshworkCanal of Schlemm
9 Angle-closure Glaucoma The iris is displaced forwardUsually due to iris thickening caused by pupil dilationThe angle is closed so aqueous humor cannot flow in to the trabecular meshworkRapid buildup of aqueous humor in the anterior chamber
10 Open-angle Glaucoma The iridocorneal angle remains open Trabecular meshwork abnormality decreases the rate of aqueous humor reabsorptionGradual buildup of aqueous humor
11 QuestionTell whether the following statement is true or false. Angle-closure glaucoma results in gradual buildup of aqueous humor in the anterior chamber.
12 AnswerFalse Rationale: Open-angle glaucoma results in gradual buildup of aqueous humor in the anterior chamber (because the iridocorneal angle stays open). In angle-closure glaucoma, the iridocorneal angle is closed, so the aqueous humor accumulates quickly.
13 Lens DisordersDisorders of refractionHyperopiaMyopiaAstigmatismDisorders of accommodationPresbyopiaCataracts
14 Retinal Blood SupplyRetinal artery enters the eye through the center of the optic nerveRetinal vein leaves the eye through the same nerveThe retina has a second blood supply from the choroid blood vessels directly behind it
15 Normal Appearance of the Retina Optic nerve enters at the optic diskRetinal arteries and veins can be seen at the center of the optic diskRetinal blood vessels are smooth with relatively straight paths
16 QuestionWhat vessel(s) supply blood to the retina?Retinal arteryChoroid vesselsOptic arteryAll of the abovea and b
17 Answera and bRationale: The retina receives blood from the retinal artery (mainly), and secondarily from the choroid vessels that are posterior/dorsal to it.
18 Papilledema or Choked Disk Increased intracranial pressure affects the optic nerveOptic disk protrudes into eye, with blurred marginsBlood vessels in its center are not distinct; the pressure has made them collapse
19 Damage to small retinal blood vessels RetinopathyDamage to small retinal blood vesselsMicrohemorrhages“Cotton-wool” exudateMicroaneurysms
20 Retinopathy (cont.) Neovascularization New vessels are more fragile New vessels attach too tightly to the vitreous, fusing it to the retina
21 Retinal DetachmentRetina is separated from the choroid blood vessels behind itRetinal cells lack oxygenCannot make enough ATPStop functioningPainless loss of vision in the part of the retina that is detached
22 Macular Degeneration Dry Degeneration of retinal cells Wet Neovascularization of the choroidBlood vessels leakFluid buildup pushes retina away from choroid
23 QuestionWhich retinal disorder is caused by ischemia of the retina?PapilledemaRetinopathyRetinal detachmentMacular degeneration
24 AnswerRetinal detachmentRationale: In this disorder, the retina becomes detached/removed from the blood vessels behind it (choroid vessels). Because the blood supply is diminished, less oxygen travels to retinal cells. Oxygen and glucose are needed to make ATP (energy); without oxygen, ATP can’t be produced, and the cells die.
25 What are the possible explanations for this client’s visual problems? ScenarioMrs. X is 47 years old and has been having trouble with her eyes; she says that she has trouble focusing and has had to get reading glassesA few weeks ago she had an episode of “sparkling” in her left eye, and now there seems to be a shadow in her vision from that eyeQuestion:What are the possible explanations for this client’s visual problems?
26 Scenario (cont.)She did not have a detached retina but has returned to her doctor because the episode recurred and this time has not gone awayWhen the doctor tests her vision, she has identical defects in the right superior visual field of both eyesQuestion:What might be going wrong?
27 DiscussionArrange the structures of the optic neural pathways in the correct order.Optic nerveLateral geniculate nucleusOptic radiationOptic chiasmEyeOptic tractVisual cortex2563147
29 DiscussionList the structures a sound wave goes through as it enters the ear.Which structures:Direct the sound wave?Transmit the sound wave?Create a nerve impulse in response to the sound wave?
30 Middle Ear Conducts sound from eardrum to inner ear Eustachian tube lets air in and out to maintain equal pressure on both sides of eardrum
31 Middle Ear infectionIf the Eustachian tube becomes blocked, fluid builds up in the middle ear. This creates a haven for bacteria and viruses, which can cause infection. Doctors can detect fluid in the middle ear with a pneumatic otoscope. This device blows a small amount of air at the eardrum, making the eardrum vibrate. If fluid is present, the eardrum will not move as much as it should.
32 Ear tubes, or tympanostomy tubes If your child has recurrent ear infections or fluid that just won’t go away, hearing loss and a delay in speech may be a real concern. One solution is for your doctor to insert small tubes through the eardrum. Ear tubes let fluid drain out of the middle ear and prevent fluid from building back up. This can decrease pressure and pain, while restoring hearing. The tubes are usually left in for 8 to 18 months until they fall out on their own.
33 Middle Ear Disorders Problems with pressure in the middle ear Patent eustachian tube, eustachian tube obstruction, acute otitis mediaProblems with adhesions between the ossiclesAdhesive otitis media, otosclerosisProblems with erosion of the tissuesCholesteatoma, mastoiditis
34 Conductive Hearing Loss Ossicles do not conduct sound from eardrum to inner earSounds that enter through the ear sound faintSounds that are conducted through other bones of the head sound louderChewingOwn voice
36 Disorders of the Inner Ear and Auditory Pathways Increased nerve firingTinnitusFocal seizuresDecreased nerve firingSensorineural deafnessPresbycusis
37 QuestionWhich auditory disorder is characterized by increased firing of the otic nerve, causing “ringing” in the ears?OtosclerosisConductive hearing lossTinnitusSensorineural deafness
38 AnswerTinnitusRationale: Increased firing of neurons of the inner ear results in the classic symptom of “ringing” in the ears. Sensorineural deafness is caused by less frequent firing of neurons in the inner ear; otosclerosis is caused by adhesions between the ossicles in the middle ear; conductive hearing loss is the result of the ossicles’ inability to conduct sound from the eardrum to the inner ear.
39 Vertigo Motion sickness Meniere disease Benign paroxysmal positional vertigoCentral vestibular disordersSudden dizziness when positioning head to certain position