Follicles and related structures in the pars intermedia of the adenohypophysis of the jird (Meriones unguiculatus).

Two types of follicle composed of non-granulated cells are regularly found in the pars intermedia of the mature jird (Meriones unguiculatus). A few (Type I) are large and cystic with a flattened epithelium bearing some microvilli, but most (Type II) are small and irregular in shape with a cuboidal to low columnar epithelium bearing many microvilli. They are apposed to the granulated chief cells, and contain a strongly PAS-positive material, but no cell debris. The Type II follicles also show crystalloid strands or chains. Villous projections sometimes protrude from the pars nervosa into the follicular lumen. The follicular cells show pinocytotic vesicles, complex interdigitations and invaginated nerves.