Study Of The Distribution And Culture Of The Stem Cells In The Tympanic Membrane

Part 1Spontaneous healing of various types of rat tympanic membrane perforationObject: To investigate the spontaneous healing process of various types of rat tympanic membrane perforation, study the perforation healing mechanism. Methods: 50 rats were divided into five groups in randomization, and performed respectively 2.5mm perforation and 1mm small perforation in the center of tympanic membrane pars tensa, 1.5mm posterior marginal perforation in pars tensa, the handle of malleus cauterized with chromic acid after tympanic membrane 3/4 excision, 1.5 mm small perforations in the center of pars flaccida, 8 ears of the first group after perforations healed were perforated once more. The histology of the perforations healing process was observed with light microscope. Results: The epithelia retracted in the early stage after perforation. The epithelia near the annulus and manubrium showed hyperplasia, they migrated to margin of the perforations and closed the perforations. The epithelia hyperplasia also appeared the intact annulus region remote to the perforation. The middle connective tissue layer reacted later than the epithelial layer. The defects were closed first by the accumulation of the epithelial cells. The difference of healing time had no statistics significance between the big and small perforations. There was no epithelial proliferation in the pars flaccida if the perforation is in the pars tensa. One ear perforated, the other side intact ear appears no change. The epithelia didn't migrate into the tympanic cavity in the posterior marginal perforations. All the perforations healed after the manubriums of the malleus were damaged. Perforations in pars flaccida healed more quickly, the healing process differed from pars tensa and fiber proliferation was apparent. Conclusions: The normal migration of the epithelia of the tympanic membrane played an important role in the healing of perforation. The generation center was located near tympanic annulus and manubrium of the malleus, the protection of these two regions was very important in the middle-ear surgery.Key words: tympanic membrane , perforation , epithelia migration...