The pars intermedia (PI) lies between the pars distalis (PD)
and the pars nervosa (PN), with many of its basophilic cells
(B) usually invading the latter. Remnants of the embryonic
hypophyseal pouch’s lumen are usually present in this
region as colloid-filled cysts (C) of various sizes. Function of
this region in humans is not clear. X56. H&E