Week 6 Lecture 2 PDF - Applied Pathophysiology

Lecture Material is adapted from © 2022 Wolters Kluwer Health, Lippincott Williams & Wilkins Applied Pathophysiology: A Conceptual Approach to the Mechanisms of Disease Chapter 12: Altered Somatic and Special Sensory Function Module 2: Alterations in Vision Module 3: Alterations in Hearing and Ba...

Lecture Material is adapted from © 2022 Wolters Kluwer Health, Lippincott Williams & Wilkins Applied Pathophysiology: A Conceptual Approach to the Mechanisms of Disease Chapter 12: Altered Somatic and Special Sensory Function Module 2: Alterations in Vision Module 3: Alterations in Hearing and Balance Dr. Romeo Batacan Jr. MPAT12001 Medical Pathophysiology Lecture Series Copyright © 2017 Wolters Kluwer Health | Lippincott Williams &Wilkins Alterations in Visual Function: Errors in refraction Myopia: nearsighted Eye focuses an image in front of retina Correction: biconcave lens to promote divergence of light  Alterations in Visual Function: Errors in refraction Hyperopia: farsighted Focusing image behind the retina Correction: biconvex lens promote the convergence of light  Alterations in Visual Function: Errors in refraction http://www.aao.org/eye‐ health/diseases/what‐is‐astigmatism Astigmatism Irregular curvature of the lens Prevents the focusing of an image Blurring vision http://www.aoa.org/patients‐and‐ Cause: corneal scar or scattering in public/eye‐and‐vision‐ problems/glossary‐ of‐eye‐and‐vision‐ conditions/astigmatism?sso=y the crystalline lens Correction: glasses, contact lenses, surgery Presbyopia Farsightedness associated with ageing Inability of the ciliary muscle and lens to accommodate for near vision Correction: bifocals http://www.opticaloutlet.ca/eyes_over_40/  Alterations in Visual Function: Alterations in Eye Movement Strabismus (“crossed eyes”) Misalignment of visual axes results in inability to focus on a single object (there are many types) Lack of coordinated extraocular muscle function Prevents the eyes in lining up in the same direction Amblyopia (“lazy eye”) Loss of visual detail from uncoordinated eye movement and focus Visual axes are misaligned in children May result from strabismus to avoid diplopia The brain suppress one of the images Visual impairment of the ignored eye From dimness of vision to permanent loss of one eye Impairment may not be fully correctable http://www.aapos.org/terms/conditions/21  Alterations in Visual Function: Alterations in Eye Movement Diplopia Perception of 2 images of a single object Images fall on non‐corresponding areas of the retina May be the result of strabismus Lack of coordination of extraocular muscle Paretic: partial paralysis https://en.wikipedia.org/wiki/Diplopia  Alterations in Visual Function: Alterations in Eye Movement Nystagmus Involuntary oscillation of the eye Caused by abnormal functioning of the Brain Labyrinth of the inner ear https://en.wikipedia.org/wiki/Nystagmus Vestibular pathways responsible for controlling eye movement Congenital: oculomotor abnormalities during neural development Acquired (post‐natal): any visual input disruptions  Alterations in Visual Function: Alterations in Protective structures Conjunctiva: Transparent mucous membrane Produces a lubricating mucous secretion 1. Palpebral conjunctiva lines eyelids 2. Bulbar conjunctiva covers white of eyes Conjunctival sac ‐ between palpebral and bulbar conjunctiva Conjunctivitis (“pink eye”): Inflammation of the mucous membrane lining the eye 1. Viral 2. Bacterial 3. Allergic Marieb EN, Hoehn KN. Human Anatomy & Physiology. 9th ed. Boston, Pearson Education; 2013 Alterations in Visual Function: Alterations in Protective structures Type Viral Bacterial Allergic Affected eye Usually Usually Usually affects: affects: affects: both (2) eyes only 1 both (2) eye eyes Manifestations Excessive eye watering Heavy discharge Itching, redness Small amount of Excessive tearing discharge Transmission Highly contagious Contagious, direct Not contagious Porth C. Pathophysiology : concepts of altered health states. 7th ed. Philadelphia, Lippincott Williams & Wilkins; 2005. Cataract Clouding of lens Altering vision focus by scattering incoming light Protein component of lens (crystallin) clumps or aggregate Increasing opaque area, increasing impairment Marieb EN, Hoehn KN. Human Anatomy & Physiology. 9th ed. Boston, Pearson Education; 2013  Alterations in Hearing and Balance Conductive hearing loss Obstruction Trauma Inflammation Alterations in Hearing and Balance: Outer ear Disorders of ear canal often caused by Obstruction: diminish the movement of sound to the middle ear Accumulation of Cerumen (wax): Presence of tumor (mass): surgical excision Inflammation: diminish the movement of sound to the middle ear Otitis externa (swimmer’s ear): infection/non‐infectious etiology  Alterations in Hearing and Balance: Middle ear Obstruction: Eustachian tube (ET) dysfunction Abnormally patent ET promote fluid movement from nasopharynx into middle ear Children crying may precipitate the movement Hearing loss is the result: Loss of tympanic membrane mobility Ear fluid, exudates compromising the conduction of vibration in the ossicles Negative pressure alters vibration  Alterations in Hearing and Balance: Middle ear Trauma: Barotrauma Injury resulting from the inability of the ear to equalize barometric stress Barometric stress: sudden changes in atmospheric pressure Air travel, sea diving Risk: upper respiratory infection, limited ability to normalize pressure  Alterations in Hearing and Balance: Middle ear Inflammation Otitis media Result of sore throat Most frequent cause of hearing loss in children (shorter, more horizontal pharyngotympanic tubes) Most treated with antibiotics Myringotomy to relieve pressure if severe Mastoiditis Bacterial infection causing inflammation of the air cells May result as complication of otitis media Otosclerosis Autosomal‐dominant condition Most common cause of chronic, progressive conductive hearing loss Slow formation of spongy bone at oval window  Alterations in Hearing: Inner Ear Hearing loss caused by inner ear dysfunction Sensorineural hearing loss: usually irreversible Cochlear hair cells destruction Neural pathway damage (auditory nerve and pathway) Can be due to aging, vascular causes, trauma, tumors, cochlear infection/inflammation, ototoxic drugs Tinnitus: symptom Perception of abnormal ear or head noise, not produced by external stimuli Underlying mechanism is unknown Often accompanies hearing disorders, sensorineural hearing loss  Alterations in Balance: Inner ear Disorders of the vestibular function ‐ signals from vestibular apparatus are distorted Ménière disease Severe vertigo associated with progressive sensorineural hearing loss, tinnitus Overproduction of endolymph Decreased absorption of endolymph Labyrinthitis: Inflammation of labyrinth Precipitate vertigo and sensorineural hearing loss Types of hearing loss Based on the identification of the event or structure involved: 1. Conductive hearing loss localized to the outer or middle ear temporary or permanent. 2. Sensorineural hearing loss often permanent resulting from disease, trauma, or genetic inheritance of a defect in the cochlea nerve cells inner ear or the auditory nerve is usually involved 3. Mixed hearing loss combination of both sensorineural and conductive hearing loss 4. Central auditory processing disorder alteration in auditory signal processing in the brain Chemical senses 1. Smell: Olfaction 2. Taste: Gustation Chemoreceptors respond to chemicals in aqueous solution Smell receptors: airborne chemicals dissolved in fluids coating nasal membranes Taste receptors: food chemicals dissolved in saliva Senses of smell and taste are linked If one impaired, the other is also affected Not life‐threatening Impact on quality of life Alterations of Taste Taste disorders are not common 1. Hypogeusia: decrease in taste sensation 2. Ageusia: absence of taste 3. Parageusia: perversion of taste, substances possess unpleasant flavor Marieb EN, Hoehn KN. Human Anatomy & Physiology. 9th ed. Boston, Pearson Education; 2013 Alterations of the Chemical Senses: Smell 1. Hyposmia: impaired smell 2. Anosmia: no smell 3. Hallucinations: hyperactivity of cortical neurons ‐ Uncinate fits 4. Parosmia: abnormal or perverted sense of smell Chemical senses—few problems occur until fourth decade, when these senses begin to decline Odor and taste detection poor after 65