Pars intermedia is the boundary between the anterior and posterior lobes of the

pituitary In vertebrate anatomy, the pituitary gland, or hypophysis, is an endocrine gland, about the size of a chickpea and weighing, on average, in humans. It is a protrusion off the bottom of the hypothalamus at the base of the brain. The hypop ...

. It contains

colloid A colloid is a mixture in which one substance consisting of microscopically dispersed insoluble particles is suspended throughout another substance. Some definitions specify that the particles must be dispersed in a liquid, while others extend ...

-filled

cyst A cyst is a closed sac, having a distinct envelope and cell division, division compared with the nearby Biological tissue, tissue. Hence, it is a cluster of Cell (biology), cells that have grouped together to form a sac (like the manner in which ...

s and two types of cells -

basophil Basophils are a type of white blood cell. Basophils are the least common type of granulocyte, representing about 0.5% to 1% of circulating white blood cells. However, they are the largest type of granulocyte. They are responsible for inflammator ...

s and

chromophobe A chromophobe is a histological structure that does not stain readily, and thus appears relatively pale under the microscope. Chromophobe cells are one of three cell stain types present in the anterior and intermediate lobes of the pituitary gland ...

s. The cysts are the remainder of Rathke’s pouch. In human

fetal A fetus or foetus (; plural fetuses, feti, foetuses, or foeti) is the unborn offspring that develops from an animal embryo. Following embryonic development the fetal stage of development takes place. In human prenatal development, fetal develo ...

life, this area produces

melanocyte stimulating hormone The melanocyte-stimulating hormones, known collectively as MSH, also known as melanotropins or intermedins, are a family of peptide hormones and neuropeptides consisting of α-melanocyte-stimulating hormone (α-MSH), β-melanocyte-stimulating h ...

or MSH which causes the release of melanin pigment in skin melanocytes (pigment cells). However, the pars intermedia is normally either very small or entirely absent in adulthood. In lower vertebrates (fish, amphibians) MSH from the pars intermedia is responsible for darkening of the skin, often in response to changes in background color. This color change is due to MSH stimulating the dispersion of melanin pigment in dermal (skin) melanophore cells.

External links

* * * * {{Authority control Endocrine system Human head and neck