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chromosomes
- -structures that carry DNA inside cells
- -humans have 46 grouped into 23 pairs
- -23rd is sex linked chromosomes
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Gene
segment of DNA on a chromosome that determines a trait
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alleles
- -diff. forms or values of a gene that an individual may posses (blue/brown eyes)
- -one comes from mom, one from dad
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homozygous
the 2 alleles are the same
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heterozygous
the 2 alleles are different (one will be dominant)
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hemizygous
only 1 allele is present
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patterns of inheritance
- -autosomal dominant
- -autosomal recessive
- -X-linked recessive
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autosomal dominant
- -abnormal gene on an autosomal chromosome
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even if child receives only one of bad gene they are going to have the disorder
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Autosomal recessive
- -involves abnormal gene on an autosomal chromosome-defect only occurs if child receives two abnormal copies of the gene
- -can be a carrier for the gene
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X-linked recessive
- -sex linked recessive
- -abnormal gene on the X chromosome
- -in males a single abnormal gene will result in the defect since they only have one X
- -in females only occurs if receive abnormal defect from both parents
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Mitochondrial inheritance
- -small amt. of DNA stored in mitochondria of a cell
- -mito. passed on by mom
- -100% of kids will inherit that DNA but only females will pass it on
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Genetic Hearing Loss
- two types:
- -syndromic
- -non-syndromic
- -50% of HL is genetic, most often autosomal recessive, nonsyndromic
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syndromic HL
- -there are other medical problems in addition to HL
- -may be autosomal recessive, autosomal dominant, or X linked
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Outer Ear
- -two parts: pinna, ear canal
- -protection, amplification, sound localization
- -Ear Canal (EAM)-outer 1/3 cartilage, inner 2/3 bone
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Conductive HL
- -HL that's a result of a problem conducting sounds to the inner ear
- -problems with outer and middle ear result in a conductive HL
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Congenital Anomalies
- -dysplasia- abnormal development of an anatomical structure
- -aplasia- lack of development
- -microtia- small pinna
- -anotia- pinna is absent
- -aural atresia- absence of ear canal
- -aural stenosis- narrow ear canal
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Congenital Aural atresia
- -usually unilateral
- -males>females
- -usually present with microtia
- -can cause variable degrees of conductive HL
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surgical outer ear reconstruction
- -rib graft auricular reconstruction- start at 6 yrs, 3-4 surgeries
- -Medpor (porous polyethylene) auricular reconstruction- start 3 yrs, 2 surgeries
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auricular prosthesis
- -appropriate for patients with anotia
- -made of silicone
- -attached with adhesive or titanium screws
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Exostosis (surfers ear)
- -abnormal bony growth on ear canal
- -encouraged by swimming in cold water
- -makes it easier for ear to become blocked by wax or debris
- -surgically removed
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External Otitis
- -swimmer's ear
- -involves pain swelling, drainage, itching, and HL
- -antibiotic drops
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