In humans, a specific portion of the adenohypophysis is almost merged with the pars distalis. This portion secretes a hormone that acts on melanocytes and regulates the pigmentation of the skin. Identify this specific anatomical region.

Step-by-step solution

Anatomically, the pituitary gland is divided into adenohypophysis and neurohypophysis. The adenohypophysis consists of two portions, pars distalis and pars intermedia. In humans, the pars intermedia is almost merged with the pars distalis. The pars intermedia secretes only one hormone called Melanocyte Stimulating Hormone (MSH). MSH acts on melanocytes (melanin-containing cells) and regulates the pigmentation of the skin. Answer: Pars intermedia