BGDB Face and Ear - Fetal
Practical 6: Trilaminar Embryo | Early Embryo | Late Embryo | Fetal | Postnatal | Abnormalities |
Fetal Growth
<html5media height="480" width="400">File:fetal growth.mp4</html5media>
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In this cartoon movie of fetal growth, observe the changing relative sizes of the head, body and limbs.
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Fetal Head Growth
Head Circumference Growth (both gestational and post-fertilisation ages are shown)
Skull Ossification
These are 2 views of the same 12 week 92 mm CRL human fetus head, double stained to show both cartilage (blue) and newly-formed bone (red). The head undergoes two different forms of ossification (endochondral and intramembranous) in separate regions of the skull.
Late Fetal Skull
Mandible Ossification
Face
The cartilage template of the mandible and the base of the skull are replaced by early bone development.
Selected midline medial head view showing key features of head musculoskeletal and neurological development.
Note extensive nasal cartilage, nasal conchae, pituitary, secondary palate, oral cavity, tongue, mandible, hyoid, choana, oropharynx.
Also note the developing tongue musculature and its mandibular attachment site.
Note that the cranial vault, the portion of the skull enclosing the brain, ossifies by a unique bone formation process, intramembranous ossification.
Because the head contains many different structures also review notes on Special Senses (eye, ear, nose), Respiration (pharynx), Integumentary (Teeth), Endocrine (thyroid, parathyroid, pituitary) and Musculoskeletal (tongue, skull).
Palate Development
Secondary palate formation is the growth of the palatal shelves towards the midline.
Inferior view | Anterior view |
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<html5media height="400" width="400">File:Palate_001.mp4</html5media> | <html5media height="400" width="400">File:Palate_002.mp4</html5media> |
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Palate Overview
Embryonic
Fetal
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Week 10 Gestational Age (GA week 12)
hard palate |
soft palate |
Adult Palate
Hearing
- Week 9 - Mesenchyme surrounding membranous labryinth (otic capsule) chondrifies.
- Week 12-16 - Capsule adjacent to membranous labryinth undegoes vacuolization to form a cavity (perilymphatic space) around membranous labrynth and fills with perilymph.
- Week 18 - ectodermal plug in external auditory meatus breaks down.
- 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.
- Week 18 - 22 - Organ of corti structural elements develop. (GA 20 - 24 weeks)
- 3rd Trimester - Vibration acoustically of maternal abdominal wall induces startle response in fetus.
Organ of Corti
Early fetal cochlea week 8.4 (GA 10.4) and week 10 (GA 12)[1]
Note Kölliker’s organ (KO), a transient epithelial structure that is the source of the future sensory cells.
Week 8.4 | Week 10 |
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Adult organ of Corti (mouse) that develops through the fetal period.
- Links: Inner Ear Development
Central Pathway
Additional Information
Additional Information - Content shown under this heading is not part of the material covered in this class. It is provided for those students who would like to know about some concepts or current research in topics related to the current class page. |
Fetal Organ of Corti Development
Week 18 | Week 20 | Week 22 |
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Fetal Auricle Development
External Auditory Meatus Timeline
Time | EAM Appearance |
Embryonic period | Ectodermal cells proliferate and fill the entire lumen forming a meatal plug |
10 weeks | Meatal plug extends in a disc-like fashion. In the horizontal plane the meatus is boot-shaped with a narrow neck and the sole of the meatal plug spreading widely to form the future tympanic membrane medially. Proximal portion of the neck starts to be resorbed. |
13 weeks | Disc-like plug innermost surface in contact with the primordial malleus, contributes to the formation of the tympanic membrane. |
16.5 week | Meatus is fully patent throughout its length, lumen is still narrow and curved. |
18 week | Meatus is already fully expanded to its complete form. |
Based on data from PMID 1441991
Practical 6: Trilaminar Embryo | Early Embryo | Late Embryo | Fetal | Postnatal | Abnormalities |
BGDB: Lecture - Gastrointestinal System | Practical - Gastrointestinal System | Lecture - Face and Ear | Practical - Face and Ear | Lecture - Endocrine | Lecture - Sexual Differentiation | Practical - Sexual Differentiation | Tutorial
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Cite this page: Hill, M.A. (2024, June 27) Embryology BGDB Face and Ear - Fetal. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/BGDB_Face_and_Ear_-_Fetal
- © Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G
- ↑ <pubmed>24131517</pubmed>| Neural Dev.