Hagfishes in the genus Myxine have five or six pairs of well-vascularized gill pouches, rarely seven, associated with the pharynx
Afferent branchial ducts conduct respiratory water from the pharynx to the pouches
efferent ducts lead from the pouches to the exterior.
In hagfishes respiratory water enters the median naris and passes via a nasopharyngeal duct to a velar chamber at the anterior end of the pharynx
The pharyngocutaneous duct appears to be a
modified last gill pouch.
Periodically, debris or particles too large to enter the afferent branchial ducts are forcefully ejected through the pharyngocutaneous duct in a manner some what analogous to coughing.
