Human anatomy, including structure and development and practical considerations . s the tympanic membrane its normal position, these movements are re-versed. When on the other hand the tympanic meml)rane is moved outward, the movement ofthe process of the incus is very slii^ht because of the unlockinj^ of the malleo-incudal articu-latit)n. Contraction of the tensor tympani nuiscle draws the centre of the tympanic membraneinward and in this way increases the tension of the membrane and of the posterior |)art ofthe axial ligament of the malleus, especially of its external portion.
Human anatomy, including structure and development and practical considerations . s the tympanic membrane its normal position, these movements are re-versed. When on the other hand the tympanic meml)rane is moved outward, the movement ofthe process of the incus is very slii^ht because of the unlockinj^ of the malleo-incudal articu-latit)n. Contraction of the tensor tympani nuiscle draws the centre of the tympanic membraneinward and in this way increases the tension of the membrane and of the posterior |)art ofthe axial ligament of the malleus, especially of its external portion. Contraction of the stapediusnuiscle pulls the head of the stapes backward, thus tilting the anterior end of the foot-platj out-ward, the posterior end acting as a fulcrum. The Mucous Membrane of the Tympanum.—The tympanic cavity islined l>v a thin transparent ninccjus membrane, closely adherent to tlie periosteumand continnons with that of the Eustachian tube and anteriorly, and Fig. 1260. stapediusmuscle Posterior cms ofstapes P^/ VestibulFootplate of xJMi. Lower end ofincus Malleus handle Internal .Tiidito-ry canal Cochlear nerve Kasal turn ofcochlea Tympanic ca\-ity Horizontal section through human middle and internal ear; stapes occhides o\a! window. X 5!^. Drawn from preparation made by Dr. Ralph Butler. with that of the mastoid cells posteriorly. It covers the ossicles and their ligaments,the muscles, the tendons and the chorda tympani nerve, and forms a number of foldsextending across the cavity. These folds vary in location, direction and number,and form pouches within the tympanum. The attic is divided into an external and an internal compartment by the incus,the head of the malleus, the superior ligament of the malleus and the superior malleo-incudal fold of mucous membrane. The external conijxirtment is bounded on theouter side by the external tympanic wall, and is itself subdivided into a superior andan inferior sj^ace bv the external ligament of
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Keywords: ., bookauthormc, bookcentury1900, bookdecade1910, booksubjectanatomy
