n :  one of the open or potentially open clefts that occur on each side of the neck region of a vertebrate embryo between the branchial arches, are formed by the meeting of an external furrow in the ectoderm with a pharyngeal pouch, may or may not extend through from the exterior to the cavity of the mouth and pharynx, and correspond to the gill slits of fishes and amphibians - called also pharyngeal cleft , pharyngeal slit , visceral cleft  .
 
 
 
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