Embryonic development of the mouth Flashcards
What two layers compose the primitive gut in the embryo?
Splanchnic mesoderm (outer) and endoderm (inner)
What does the dorsal mesentery derive from?
Mesoderm
Name four structures that derive from the foregut
Mouth Oesophagus Pharynx Liver and pancreas Stomach Most of the SI
Name three structures that derive from the hindgut
Ileum
Large intestine
Cloaca
What depression in the cranial embryo indicates the developing oronasal cavity?
Stomodaeum
What is another name for the oral plate? What forms it? What structures in the adult indicate where it used to be?
A.k.a the pharyngeal membrane
Formed from ectoderm of stomodaeum and endoderm of foregut
Pharyngeal arches
What layer is the inner lining of the mouth derived from? From which point along the GIT does this change?
The ectoderm - from the laryngopharynx onward is endoderm
Where do the pharyngeal arches come from? How many are there, and what do they form?
They are migrating cells of the neural crest
Six in total, though number 5 usually atrophies
Form structures of the head and neck
Which arches become cartilage of the larynx?
4 and 6
Which arches become the hyoid bones?
2 and 3
Which arch becomes the maxilla + mandible?
1
Which four structures does arch 1 form initially?
Left and Right maxillary and mandibular processes
What develops immediately above the maxillary process?
The frontonasal prominences
What does the frontonasal prominence include?
Frontal process
Left and right naso-lateral and naso-medial processes
What fuses to form the upper jaw?
The L and R nasomedial and maxillary processes
What fuses to form the nose?
The L and R frontal processes and nasolateral processes
What fuses to form the lower jaw?
The L and R mandibular processes
What fuses to form the nasolacrimal duct?
The lateral nasal prominence and the maxillary prominence - endoderm between canalises to create the duct
What produces the interspecies variation in the upper lip (philtrum vs no philtrum)
Variation in degree of fusion of medial nasal prominences
What is the term for ‘long’ faced (normal)
Dolocephalic
What determines face length?
The growth of the maxillary and mandibular processes - everything else will follow
Which two processes failed to fuse in ‘facial cleft’?
Maxillary and nasolateral processes (nasolacrimal duct failed to form)
Which two processes failed to fuse in cheiloschisis?
Maxillary and nasomedial processes
What are the three parts that fuse to form the palate?
Left palatine process
Right palatine process
Median palatine process/intermaxillary palatine process