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Period: to
Hearing Fetal Development
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3rd week
Otic Placode, Otic Vesicle -
5th Week
cochlear part of otic vesicle elongates (humans 2.5 turns) left Ventrolateral view of the whole embryo with 5-mm scale bar. At this stage of development no middle or external ear structures are apparent and will be derived later from pharyngeal arches one and two (labeled). The gray bar through the head indicates the plane of cross-section (right). right A cross-section of the head showing the size and position of the otic vesicles. -
Week 5-8
Centres of ossification appear in remaining cartilage of otic capsule form petrous portion of temporal bone. Continues to ossify to form mastoid process of temporal bone. -
9th Week
Mesenchyme surrounding membranous labryinth (otic capsule) chondrifies
A. Lateral view of the whole embryo with 5 mm scale bar. Note the well developed external ear with simplified adult structure and narrower meatal opening. B. Cross-section of the head at the plane of the skull base and oral cavity to the top.
C. The gray box indicates this region: detail of inner and middle ear development. The middle ear cavity has not yet formed. -
week 12-16
Capsule adjacent to membranous labryinth undegoes vacuolization to form a cavity (perilymphatic space) around membranous labrynth and fills with perilymph -
2nd Trimester 16-24
Centres of ossification appear in remaining cartilage of otic capsule form petrous portion of temporal bone. Continues to ossify to form mastoid process of temporal bone -
3rd trimester 27-40
Vibration acoustically of maternal abdominal wall induces startle response in fetus.
