Midfollicular

Midfollicular is a descriptive term used in dermatology and histology to refer to the middle portion of the hair follicle. It denotes a region roughly equidistant from the follicle opening at the skin surface (the infundibulum) and the deepest section near the hair bulb. The term is not part of the formal anatomy taxonomy, and its exact boundaries can vary among authors and studies. In practice, researchers may use midfollicular to describe the localization of cells, proteins, or morphological features observed in sections of the follicle, when these features lie neither in the upper isthmus nor in the deepest regions.

In histology, the midfollicular region can include portions of the outer root sheath and the proximal segments of the inner root sheath, depending on the plane of section used by the study. The term is chiefly of research utility rather than a clinical diagnosis, and is used to provide spatial context in descriptions of follicle structure and function. It serves to indicate position within the follicle for observations such as staining patterns or cellular activity.

Midfollicular should not be confused with the phases of the hair growth cycle, which are anagen, catagen, and telogen. The midfollicular region can be relevant in studies of follicle development, aging, injury response, or localization of proteins during normal cycling or pathology. Related terms include infundibulum, isthmus, bulge, outer root sheath, and inner root sheath.