Oesophageal pouch
Anatomical feature in molluscs
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The oesophageal pouches (also known as sugar glands)[1] are a pair of pouches connected to the oesophagus of all molluscs, and represent a synapomorphy of the phylum.[2]
Morphology
Usually forming a pair of lateral structures, oesophageal pouches take various forms, but usually account for a fair portion of the anterior volume of the creeping molluscs and scaphopods.[3][4][5][6][7] There is a single pouch ventral to the rear of the radula in some nudibranch sea slugs.[6] The pouches are lined with ciliated secretory cells.[8]
Function
Occurrence
The features are considered ancestral to molluscs[2] and are present in monoplacophorans,[9] but have been secondarily lost in the Heterobranchia.[10] However, it is not certain that all oesophageal diverticulae are homologous.[11][12]