BGDB Face and Ear - Early Embryo
During week 4 a number of features appear visible on the embryo surface:
- At the level of the body heart, liver, somite bulges and limb buds appear.
- At the level of the head sensory placodes and pharyngeal arches appear.
Carnegie Stage 12 to 14
This is a scanning EM of the embryo superior dorsal view showing the paired otic placodes sinking into the surface at the level of the hindbrain between day 24 and day 25
|Human Embryo (Stage 11)|
Sensory placodes develop as small patches of ectodermal thickenings.
The placodes are laterally paired and contribute key components to sensory structures of the ear, eye and nose.
Named by the sensory system and components they will form: otic placode, optic (lens) placode and nasal placode.
Identify the structure and position of the otic vesicle (otocyst) relative to other head structures.
Later week 5 development showing a sagittal section upper half of human embryo.
Stage 13 Pharyngeal Arches
Look through the above cross-sections of the stage 13 embryo observing and identifying structures of the face and ear visible at this stage.
Structures derived from Arches
|Pharyngeal Arch||Nerve||Artery|| Neural Crest
|trigeminal (V)||maxillary artery (terminal branches)||mandible, maxilla, malleus, incus||muscles of mastication, mylohyoid, tensor tympanic, ant. belly digastric||ant lig of malleus, sphenomandibular ligament|
|facial (VII)|| stapedial (embryonic)
|stapes, styloid process, lesser cornu of hyoid, upper part of body of hyoid bone||muscles of facial expression, stapedius, stylohyoid, post. belly digastric||stylohyoid ligament|
|3||glossopharyngeal (IX)||common carotid, internal carotid arteries||greater cornu of hyoid, lower part of body of hyoid bone||stylopharyngeus|
|4||vagus (X) superior laryngeal branch||part of aortic arch (left), part right subclavian artery (right)||thyroid, cricoid, arytenoid, corniculate and cuneform cartilages||crycothyroid, soft palate levator veli palatini (not tensor veli palatini)|
|6||vagus (X) recurrent laryngeal branch||part of left pulmonary artery (left), part of right pulmonary artery (right)||thyroid, cricoid, arytenoid, corniculate and cuneform cartilages||larynx intrinsic muscles (not cricothyroid muscle)|
- 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.
Other Sensory Systems
The links below are to additional information providing background about each of the sensory systems. Only hearing is covered in today's class.
|Vision Links: Introduction | Lens | Retina | Placodes | Extraocular Muscle | Cornea | Eyelid | Abnormalities | Student project 1 | Student project 2 | Category:Vision|
|Smell Links: Introduction | Placodes | Rhinencephalon | Head Development | Student project | Taste | Sensory Systems | Category:Smell|
|Historic Smell Embryology: 1902 Olfactory Structures | 1940 Olfactory and Accessory Olfactory Formations|
During this period neural crest cells migrate into the pharyngeal arches and other head locations, and have an important contribution to many different head structures. Neural crest cells at other levels contribute to body many structures. There are also many developmental abnormalities associated with abnormal neural crest development and/or migration. This topic is beyond the scope of the current class.
- Links: Neural Crest Development
| Cranial neural crest contribution to skeletal structures
There has been controversy about the neural crest embryonic contribution to the parietal region. A recent transcriptional analysis of second trimester human cranial compartments suggests that "a gene expression signature of neural crest origin still exists in frontal and metopic compartments while gene expression of parietal and sagittal compartments is more similar to mesoderm."
- Negar Homayounfar, Sarah S Park, Zahra Afsharinejad, Theodor K Bammler, James W MacDonald, Federico M Farin, Brigham H Mecham, Michael L Cunningham Transcriptional analysis of human cranial compartments with different embryonic origins. Arch. Oral Biol.: 2015, 60(9);1450-1460 PubMed 26188427
- Fabio Santagati, Filippo M Rijli Cranial neural crest and the building of the vertebrate head. Nat. Rev. Neurosci.: 2003, 4(10);806-18 PubMed 14523380 | Nat Rev Neurosci.
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. 2017 Embryology BGDB Face and Ear - Early Embryo. Retrieved March 23, 2017, from https://embryology.med.unsw.edu.au/embryology/index.php/BGDB_Face_and_Ear_-_Early_Embryo
- © Dr Mark Hill 2017, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G