The infundibulum extends from the tuber cinereum and pierces the diaphragma sella before being surrounded by the pars tuberalis. The posterior pituitary (aka neurohypophysis) is a direct extension from the hypothalamus, connected to it via the infundibular stalk, which is also considered part of the neurohypophysis. These may give rise to Rathke cleft cystsВ (also known as pars intermedia cysts 6,7). It arises from the posterior wall of Rathke pouch and contains vestigial lumina of Rathke pouch which appears as narrow vesicles of variable length. The pars intermedia in a thin layer of epithelial cells located between pars distalis and neurohypophysis. The pars tuberalis is the part of the adenohypophysis which surrounds the anterior aspect of the infundibular stalk. It is composed of cords of epithelial cells individually specialized to secrete trophic hormones acting on various target organs (see below). It arises from the anterior wall of Rathke pouch. The pars distalis is the largest part of the pituitary gland.

The anterior pituitary is by far the largest part of the gland and is responsible for synthesis and release of most pituitary hormones (with the exception of oxytocin and antidiuretic hormone (ADH) which are released by the posterior pituitary). Not uncommonly the diaphragma sellae is incomplete (considered a normal variant) and CSF may enter into the pituitary fossa and may give rise to the ' empty sella sign' on neuroimaging. The diaphragma sellae has a variably sized opening for the infundibular stalk. The pituitary fossa is surrounded by a layer of dura, continuous with the diaphragma sellae above (the dural anatomy is discussed in more detail in the pituitary fossa article). The anterior lobe of the pituitary is surrounded by a thin fibrous capsule, similar to that of salivary glands, continuous with thin septae which extend into the gland 11. The pituitary is usually divided (in practice) into anterior and posterior parts, which actually refers to groupings of four subparts 4,5: The pituitary gland sits atop the base of the skull in a concavity within the sphenoid bone called the sella turcicaВ ( pituitary fossa), immediately below the hypothalamus and optic chiasm.

Hypothalamus hormones