Vascular Architecture of the Eustachian Tube in the Rat. —A Scanning Electron Microscopic Study—

The blood vessels of the eustachian tubes of rats were infused with methacrylate casting medium and observed three-dimensionally under a scanning electron microscope (SEM). The ascending pharyngeal artery and the ascending palatal artery gave off many branches around the nasopharyngeal orifice of the eustachian tube. The vascular architecture of the nasopharyngeal orifice was a dense network, extending to most of the other pharyngeal areas. The vascular system of the middle part of the tube was a one-layered coarse network. Arteries from the middle ear cavity and the pharynx supplied the tympanal orifice. The vascular network of this area was richer than that in other parts of the eustachian tube, and two or more vascular layers were observed clearly. From the point of view of the vascular supply, it is probable that pathological change around the nasopharyngeal orifice leads to stenosis of the tube and is related to the occurrence of lowered pressure in the middle ear cavity. However, the particular structure of the vascular layers in the tympanal orifice might also play an important role in the regulation of air pressure in the tympanic cavity.