• An experimental study of the modus operandi of tensor and levator palati muscles over the Eustachian tube was conducted in two dogs. The tensor palati muscle is divisible into four functional units: (1) anterior part, vertical fibers; (2) middle part, oblique fibers; (3) posterior part, horizontal fibers; and (4) posteriormost part, osseous origin. Though the levator palati passively fixes the medial lamina and narrows the pharyngeal ostium, it dilates the lumen of the isthmus by two mechanisms: (1) rectification of the isthmus "kink" by bringing the cartilaginous and osseous segments into a straight line; and (2) pushing away the surrounding soft tissue pressure that is being exerted over the medial wall of the tube (not protected by cartilage).
The peculiar absence of the medial cartilaginous lamina near the isthmus is attributed to the following: (1) freedom of movement of cartilaginous tube; (2) better anchorage of tubal cartilage passively by levator palati; (3) "kinking" of canal; and (4) compression of the lumen.
(Arch Otolaryngol 102:265-270, 1976)