Week 3

Question 1

3 stage of human prenatal development

Answer 1

1. pre-embryonic (week 1-3)
2. Embryonic (week 4-8)
3. Fetal (week 9- birth)

Question 2

pre-embryonic
week 1

Answer 2

zygote cleaves and forms blastocyst which forms hypoblast

Question 3

pre-embryonic week 2

Answer 3

bilaminar disc formation
form layer of epiblast

Question 4

Preembryonic week 3

Answer 4

when the neural development starts in 3 weeks
- notochord and neural plate

Question 5

when does the outer and middle ear form

Answer 5

embryonic stage and much later

Question 6

middle ear formation

Answer 6

forms from the 1st and 2nd branchial arch
- some structures come from both

Question 7

most common isolated congenital anomaly

Answer 7

disconnection between incus and stapes, long process of incus absent or abnormal, and super structures of stapes is malformed
bones don’t fuse together
cause congenital conductive HL

Question 8

malformation of ossicular chain occurs as a solitary lesion T/F

Answer 8

False it rarely occurs as a solitary lesion there is usually other temporal bone anomalies (Atresia of EAC)

Question 9

Development of pinnae

Answer 9

begins at 4 weeks
- at 3 months more mature ossicles develop quite rapidly

Question 10

cochlear development

Answer 10

starts at 7 weeks (1 turn)
10-11 weeks 2 1/2 turns
25 weeks fully mature
- organ of corti develops from thickened epitheial cells of cochlear duct

Question 11

when is the first sign of hair cell differentiation

Answer 11

9-10 weeks

Question 12

what shape is IHC

Answer 12

start cylindrical and become flattened shape

Question 13

are IHC or OHC immature for a longer period of time

Answer 13

OHCS

Question 14

how many rows of hair cells exist initially

Answer 14

2 IHC 4 OHC, overproduction followed by reabsorption may serve to slow development

Question 15

3 stages of HC innervation

Answer 15

1. before onset of function- IHC receive efferent and afferent OHC only efferent
2. onset of function
3. adult like- IHC strong afferent innervation and OHC receive large efferent connections

Question 16

anotia

Answer 16

absent pinna, 10dB hearing loss (conchae gives gain of approx 10dB at 5KHz)

Question 17

stenois

Answer 17

partial closure of ear canal

Question 18

atresia

Answer 18

complete closure of ear canal

Question 19

how much of a dB loss can a complete ear canal closure cause

Answer 19

50-60dB conductive hearing loss

Question 20

microtia

Answer 20

congenital birth defect of outer ear due to incomplete development of 1st and 3nd brachial arches before 5th week of gestation

Question 21

what are the syndromes associated with microtia

Answer 21

treacher collins
fraser
nager
goldenhar

Question 22

satyr ear

Answer 22

pinna comes out to sharp point and forward fold
- deficiency in 4th hillock during 6th and 8th week gestation
- potential localization and conductive loss issues

Question 23

stahl ear

Answer 23

abnormality in superior crus on antihelix
- may have 3rd crus
less elastic cartilage

Question 24

lop ear

Answer 24

folding down of helix and scapha

Question 25

question mark ear

Answer 25

cleft between helix and lobe - defect between 5th and 6th hillocks - occurs b.w 6th and 8th week gestation

Question 26

Darwin tubricle

Answer 26

small growth at superior point of pinna due to small growth in position of 5th hillock - autosomal dominant trait

Question 27

what % of congenital deafness is attributable to recessive genetic factors

Answer 27

80-85%

Question 28

what % of congenital deafness is attributable to dominant genetic factors

Answer 28

10%

Question 29

what % of congenital deafness is attributable to mitochondrial mutations

Answer 29

5%

Question 30

what % of congenital hearing loss is syndromic vs non-syndromic

Answer 30

30% syndromic 70% non-syndromic

Question 31

waardenburg syndrom

Answer 31

-moderate-profound hearing loss -2 different coloured eyes or unusally bright blue -white forelock premature graying - low frontal hairline - wide space inner corners of eyes

Question 32

ushers

Answer 32

autosomal recessive 3-6% deaf and 3-6% hearing impaired - type I most severe Type III least severe

Question 33

night blindness is associated with what type of ushers

Answer 33

Type III

Question 34

Type III ushers hearing loss onset is when

Answer 34

mid teens deaf by mid-late adult

Question 35

ushers Type II

Answer 35

Moderate to severe hearing loss - do well with amplification

Question 36

Type I ushers

Answer 36

profound HL and severe balance issue with little oral language (sign) and rarley walk before 18 months - progress to blindness

Question 37

non-syndromic hearing losses

Answer 37

COCH mutation GJB2-Gap junction beta 2 Connexin

Question 38

COCH mutation

Answer 38

vestibular problem onset 15-65 years

Question 39

GJB2-Gap junction beta 2

Answer 39

most common cause HL encodes protein connexin lining gap junction varying degrees of HL from mild- profound HL @ birth or shortly after

Question 40

mumps

Answer 40

low incidence of HL tinnitus and fullness common hearing loss within 2 weeks of inflammation of parotid gland, rapid onset, profound loss and permanent

Question 41

measles

Answer 41

was the most common cause of HL before vaccine - now low incidence if you did get it 45% deaf 55% mild to. moderate

Question 42

what is the inutarine background noise

Answer 42

28dBsPL, mostly less 40HZ

Question 43

external sounds that are attenuated in fetal environment

Answer 43

<250 0-2dB 1KKhZ 20dB 2-4KHZ 40dB

Question 44

asphyxia

Answer 44

lack of oxygen in utero and postnatally can cause HL