THE TYMPANIC CAVITY 



1091 



ment runs almost vertically from the superior wall of the epitympanic recess to the 

 head of the malleus (fig. 834). The anterior malleolar ligament extends from the 

 angular spine of the sphenoid bone through the petro- tympanic (Glaserian) fissure 

 to the anterior or long process of the malleus, which it surrounds, and is inserted 

 with it into the neck of the malleus. The lateral malleolar ligament is short and 

 thick, and runs from the margins of the tympanic notch (notch of Rivinus) to the 

 neck of the malleus (fig. 834) . The posterior ligament of the incus passes from the 

 fossa on the posterior tympanic wall to the crus brevis of the incus (fig. 835) . The 

 superior ligament of the incus is little more than mucous membrane; it runs from 

 the tympanic roof to the body of the incus. 



Muscles of the ossicles. — Each of the muscles of the ossicles is contained in a 

 bony canal. The tensor tympani is a pinniform muscle about 2 cm. long. It 

 arises from the cartilaginous part of the tuba auditiva (Eustachian tube) , from the 



Fig. 835. — Medial Surface of Right Membrana Tympani. (Enlarged.) 



Superior malleolar ligament Incus 



Head of malleus 



Chorda tympani nerve 

 Tendon of tensor tympani 



Manubrium of malleus 



Tensor tympani muscle 



Tuba auditiva 



Posterior ligament of incus 



Posterior portion of 

 epitympanic recess 



Base of stapes 



Lenticular process of incus 



Posterior portion of 

 membrana tympani 



adjacent part of the great wing of the sphenoid, and from the, bony walls of the 

 semicanal which encloses it. It ends in a round tendon which turns almost at right 

 angles over the cochleariform process and passes laterally across the tympanic 

 cavity to be attached to the manubrium of the malleus near the neck. It draws 

 the manubrium medially and tightens the tympanic membrane, and is supplied by 

 the motor division of the trigeminal cranial nerve, through the tei:!sor tympani 

 branch from the otic ganglion. The stapedius arises in the interior of the hollow 

 pyramidal eminence. The tendon escapes through the openings at the apex and 

 then turns inferiorly and is inserted on the posterior surface of the neck of 

 the stapes. It draws laterally the ventral border of the base of the stapes and is 

 supplied by the facial nerve. 



Vessels and nerves. — The arteries of the tympanic cavity are the anterior tympanic from 

 the internal maxillary artery (fig. 451), the stylo-mastoid from the posterior auricular artery, 

 the superficial petrosal from the middle meningeal artery, the inferior-tympanic from the 

 ascending pharyngeal (fig. 446), and the carotio-tympanic branch from the internal carotid. 

 The veins empty into the superior petrosal sinus and into the posterior facial (temporo- 

 maxillary vein). The nerves are the tympanic plexus formed by the tympanic branch of the 

 glosso-pharyngeal (p. 951), and the inferior and superior carotico-tympanic nerves which join 

 the internal carotid plexus of the sympathetic (p. 960). The small superficial petrosal nerve 

 takes its origin from the tympanic plexus, and the chorda tympani crosses the tympanic 

 cavity from the posterior to the anterior wall (p. 948, figs. 738 and 835). 



