The Eustachian tube passes between -
Superior and middle constrictors
Above superior constrictor
Middle and inferior constrictor
Below inferior constrictor
GAPS BETWEEN PHARYNGEAL MUSCLES AND RELATED STRUCTURES
I. Between the base of the skull and superior constrictor i.e. above superior constrictor (Sinus of Morgagni) :

Levator veli palatini
Auditory tube(eustachian tube)
Ascending palatine artery

II. Between superior and middle constrictors :

Stylopharyngeus muscle
Glossopharyngeal nerve

III. Between Middle and Inferior constrictors :

Internal laryngeal nerve
Superior laryngeal vessels

These structures pierce the thyrohyoid membrane.
IV. Between lower border of inferior constrictor and esophagus :

Recurrent laryngeal nerve
Inferior laryngeal vessels