2011 Lab 10 - Fetal
From Embryology
Hearing
- Week 9 - Mesenchyme surrounding membranous labryinth (otic capsule) chondrifies. (More? Human 10 Week Fetus)
- Week 12-16 - Capsule adjacent to membranous labryinth undegoes vacuolization to form a cavity (perilymphatic space) around membranous labrynth and fills with perilymph.
- Week 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 - Vibration acoustically of maternal abdominal wall induces startle response in fetus.
Central Pathway
- 26 weeks - human brainstem auditory pathway is anatomically formed.
- 28 weeks - Automated Auditory Brainstem Response ( AABR) can be recorded.
less than 34 weeks - latencies of AABR components (I, III, and V) decrease as a function of gestation
