3 ms·Mouth is the start of the hole that ends at the anus.by hgsgm 4y agoMouth is the start of the hole that ends at the anus.867-5309 4y agowhere can I buy a compendium of these definitions?frereubu 4y agoAnd AFAIK that tube is one of the first physiological structures that forms in an embryo when it folds its two sides over.