Development
Rathke's pouch, and therefore the anterior pituitary, is derived from Ectoderm
The pouch eventually loses its connection with the pharynx giving rise to the anterior pituitary. The anterior wall of Rathke's pouch proliferates, filling most of the pouch to form pars distalis and pars tuberalis. The posterior wall forms pars intermedia.
In some organisms, the proliferating anterior wall does not fully occupy Rathke's pouch, leaving a remnant (Rathke's cleft) between the pars distalis and pars intermedia.
Read more about this topic: Rathke's Pouch
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