The =pharynx= presents in its posterior part a median cul-de-sac about
an inch and a half (ca. 3 to 4 cm.) long, which is situated between the
ventral straight muscles of the head and the origin of the œsophagus.
Its lower margin is formed by the junction of the posterior pillars of
the soft palate, which contain muscular tissue derived from the
palatinus and palato-pharyngeus. The vault of the pharynx (Fornix
pharyngis) is divided by a median fold of mucous membrane which is a
direct continuation of the septum nasi. On either side of this is an
infundibulum in which the Eustachian tube opens.