TYMPANIC CAVITY OK MIDDLE EAR 



833 



of the stapes, surrounded by its ligamentum annulare. (3) An elevation, the pro- 

 minentia canalis facialis, which is situated above the fenestra vestibuli, in the 

 recessus epitympanicus ; this elevation indicates the position of the upper part of 

 the canalis facialis (O.T. aqueduct of Fallopius), which contains the facial nerve, and 





Antrum tympanicum 

 Recessus epitympanicus 

 Prominentia canalis facialis 



Tegmen tympani 



Eminentia 

 pyramidalis 



Sinus tympani 

 Mastoid air-cells 



Fenestra vestibuli 

 Semicanal for tensor tympani 



Septum canalis musculotubarii 



Promontory with 

 grooves for 

 tympanic plexus 

 Osseous part of 

 auditory tube 

 Bristle introduced into the 

 foramen for the tympanic nerve 



Fenestra cochleae 



Course of canalis facialis 



FIG. 709. SECTION THROUGH LEFT TEMPORAL BONE, showing labyrinthic wall of tympanic cavity, etc. 



is continued backwards and downwards behind the tympanic cavity, to end at the 

 stylo-mastoid foramen. (4) The septum canalis musculotubarii (O.T. processus 

 cochleariformis), which extends backwards, above the anterior end of the fenestra 

 vestibuli, where it makes a sharp lateral curve, and forms a pulley over which the 

 tendon of the tensor tympani muscle plays. (5) A funnel-shaped recess, situated 

 behind and below the promontory, and almost hidden by its overhanging edge, 

 leads to an irregularly oval opening, termed the fenestra cochleae ; in the macerated 

 bone this fenestra communicates with the cochlea, but in the recent state is closed 

 by the membrana tympani secundaria ; this membrane is bent angularly along a line 

 joining its antero-inferior two-thirds with the postero-superior third ; and consists 



Of three layers : (a) Recessus epitympanicus 



lateral, continuous 

 with the mucous 

 lining of the tym- 

 panum, and con- 

 taining a network 

 of capillaries ; (V) 

 intermediate, or 

 membrana propria, 

 the fibres of which 

 radiate chiefly 

 towards the peri- 

 phery of the mem- 

 brane some 

 branched, dendritic 

 fibres are also 

 present ; (c) medial, 

 continuous with 



the epithelial FIG. 710. LEFT MEMBRANA. TYMPANI AND RECESSUS EPITYMPANICUS, 

 lining of the 

 labyrinth. (6) Be- 

 tween the fenestra vestibuli above and the fenestra cochleae below is a small circular 

 depression, the sinus tympani, which is perforated by one or two minute foramina 

 for blood-vessels, and indicates the position of the ampullated end of the posterior 

 semicircular canal. 



54 



Pars flaccida 

 (Shrapnell) 



Anterior and posterior 

 malleolar plicae 

 Tendon of tensor 

 tympani muscle (cut) 



Manubrium mallei 



Pars tensa 



Sulcus tympanicus 



viewed 



from within. The head and neck of the malleus have been removed to 

 show the pars flaccida and the malleolar plicse. x 3. 



