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
What structure exists at the point where the three palatine constituents meet?
The incisive foramen - leads to vomeronasal organ
What is palatoschisis?
Failure of the palatine processes to fuse
What do the pharyngeal pouches form?
Auditory tube, fossae of tonsils, parathyroid thymus and thyroid glands
From which structure is the torus in ruminants derived?
The median tongue swelling
What does the proximal tongue swelling form? what about the two distal swellings?
Distal swellings together with the median swelling will form tongue body, proximal swelling will form tongue root
How do the multiple origins of the tongue relate to its innervation?
It is innervated by severeal different cranial nerves as it arises from several different places
Which germ layer are the oesophageal glands derived from?
Endoderm
Which germ layer is the oesophegeal muscle derived from?
Splanchnic mesoderm
Which mesentery of the developing stomach will become the great mesentery?
The mesogastrium - it is stretched when the stomach moves away from midline
Describe the development of the intestines
Grow much faster than embryo body length, forms a loop
Get physiological herniation into the umbilical stalk
The cranial mesenteric artery will develop from the middle of the loop
Intestinal loop twists on itself once, and the cranial arm coils extensively to form the small intestine
What is the pancreas derived from? Which part becomes which lobe?
The dorsal and ventral primordia
Dorsal => left
Ventral => right
Which structure grows to separate the urogenital from anorectal canal?
The urorectal septum
What is the name for the anal area membrane?
Proctadeum
What does the septum transversum form? What other structures contribute?
Contributes to the diaphragm, along with the two pleuropericardial folds
