EARLY ORGANOGENY 



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1st visceral pouch 



2nd visceral pouch 



Pharynx 

 3rd visceral pouch 



4th visceral pouch 

 5th visceral pouch 



Mandibular arch 

 Hyomandibular cleft 

 Hyoid arch 

 Blood vessel 

 2nd visceral cleft 

 3rd visceral arch 

 3rd aortic arch 



3rd visceral cleft 

 4th visceral arch 

 4th aortic arch 



5th visceral arch 

 '5th aortic arch 

 6th visceral arch 



Pronephric tubule 



Pronephric duct 

 Midgut 



Hindgut 



The 7 mm. frog tadpole: frontal section. 



The lateral lips of the blastopore close together over the posterior end 

 of the neurocoel above and the posterior end of the archenteron 

 below. Internally this provides a temporary (about 1 hour) connection 

 between the central nervous system (neurocoel) and the gut cavity 

 (archenteron) known as the neurenteric canal or chorda-canal. Similar 

 temporary connections of these two major systems are seen in the 



