Development of the Pineal Gland
The pineal gland (epiphysis cerebri) develops as a hollow out growth from the most caudal part of the roof plate of the diencephalon. Due to proliferation’ of the lining cells, the distal part of the outgrowth becomes solid. However, its proximal part remains hollow, forming stalk of the pineal gland which contains pineal recess of the third ventricle.
Development of the Pituitary Gland
The pituitary gland (hypophysis cerebri) is composite in its development, being derived partly from the neuroectoderm and partly from the oral ectoderm. This implies that the hypophysis is ectodermal in origin but the ectoderm is derived from two different sources: (1) A downgrowth from the neuroectoderm of the diencephalons called infundibulum (or neurohypophyseal bud) gives rise to the neurohypophysis, and (2) An outpocketing from the roof of the stomodeum called adenhypopyseal pouch or Rathke’s pouch gives rise. to the adenohypophysis.
During the fourth week a diverticulum develops in the floor of the diencephalon and grows ventrally in the direction of the stomodeum. This
neuroectodermal downgrowth is called neurohypophyeal bud or infundibulum. Simultaneously, an ectodermal pouch appears in the roof of the sto-
modeum just anterior to the buccopharyngeal membrane. This pouch, called adenohypophyseal pouch or Rathke’s pouch, grows dorsally to ward the infundibulum. As the Rathke’s pouch elongates, its distal part becomes dilated, whereas the proximal part (stalk) becomes constricted. By the 5th week the pouch loses its connection with the stomodeum and forms a sac that becomes closely apposed to the rostral surface of the infundibulum.
This sac differentiates to form various components of the adenohypophysis, whereas the infundibulum forms the neurohypophysis. The cells in the anterior wall of the Rathke’s pouch proliferate rapidly and obliterate the lumen of the pouch almost completely. These cells form the pars ‘distalis of the adenohy- pophysis. A small extension of the pars distalis grows along the infundibular stalk and surrounds it to form the pars tuberalis. The posterior wall of the
Rathke’s pouch gives rise to the thin pars intermedia, which lies between the pars distalis and neurohypophysis. The pars distalis, pars tuberalis and
pars intermedia are collectively known as adenohypophysis. The distal part of the infundibulum gives rise to the pars nervosa of the neurohypophysis. This part of the infundibulum becomes solid as the neuroepithelial cells in its wall proliferate and obliterate the lumen. These cells differentiate into pituicytes which are regarded to be a special type of neuroglial. cells. The ~roximal part of the .in:undlbulum remains as. the stalk of pituitary gland (also called.infundibular ste”!). The lumen of this stalk IS also obllter~ted as ~he aXODS from the hypothalamic nuclei pass through the infundibular stem to reach the pars nervosa of the pituitary gland. The pars nervosa and the infundibular stern are collectively known as neurohypophysis.
For more detail visit : https://embryology.med.unsw.edu.au/embryology/index.php/Endocrine_-_Pineal_Development