Posterior
On the posterior wall is a prominence, best marked in childhood, produced by a mass of lymphoid tissue, which is known as the pharyngeal tonsil.
Above the pharyngeal tonsil, in the middle line, an irregular flask-shaped depression of the mucous membrane sometimes extends up as far as the basilar process of the occipital bone; it is known as the pharyngeal bursa.
Read more about this topic: Nasopharynx