

THE AUDITORY OSSICLES 



1045 



almost horizontally backward, and is attached to the fossa incudis, in the lower 

 and back part of the epitympanic recess. 



The long eras (cms longum; long process) descends nearly vertically behind and 

 parallel to the manubrium of the malleus, and, bending medialward, ends in a 

 rounded projection, the lenticular process, which is tipped with cartilage, and 

 articulates with the head of the stapes. 



The Stapes (Fig. 918), so called from its resemblance to a stirrup, consists of a 

 head, neck, two crura, and a base. 



The head (capitulum stapedis) presents a depression, which is covered by cartilage, 

 and articulates with the lenticular process of the incus. 



The neck, the constricted part of the bone succeeding the head, gives insertion 

 to the tendon of the Stapedius muscle. 



The two crura (cms anterius and crus posterius) diverge from the neck and are 

 connected at their ends by a flattened oval plate, the base (bos-is stapedis), which 

 forms the foot-plate of the stirrup and is fixed to the margin of the fenestra vestibuli 

 by a ring of ligamentous fibers. Of the two crura the anterior is shorter and less 



rved than the posterior. 



Short cms 



Body 



Facet for 

 malleus 



Long crus 



Lenticular 

 process 



Head 



Neck 



Q. 917. Left incus. A. From within. B. From 

 the front. 



Anterior crus 

 Posterior crus 

 Base 



FIG. 918. A. Left stapes. B. Base of stapes, medial 

 surface. 



Articulations of the Auditory Ossicles (articulationes ossiculorum auditus). 

 The incudomalleolar joint is a saddle-shaped diarthrosis; it is surrounded by an 

 articular capsule, and the joint cavity is incompletely divided into two by a wedge- 

 shaped articular disk or meniscus. The incudostapedial joint is an enarthrosis, 

 surrounded by an articular capsule; some observers have described an articular 

 disk or meniscus in this joint; others regard the joint as a syndesmosis. 



Ligaments of the Ossicles (ligamenta ossiculorum auditus). The ossicles are 

 connected with the walls of the tympanic cavity by ligaments: three for the 

 malleus, and one each for the incus and stapes. 



The anterior ligament of the malleus (lig. mallei anterius) is attached by one end 

 to the neck of the malleus, just above the anterior process, and by the other to 

 the anterior wall of the tympanic cavity, close to the petrotympanic fissure, some 

 of its fibers being prolonged through the fissure to reach the spina angularis of the 

 sphenoid. 



The superior ligament of the malleus (lig. mallei superius) is a delicate, round 

 bundle which descends from the roof of the epitympanic recess to the head of the 

 malleus. 



The lateral ligament of the malleus (lig. mallei laterale; external ligament of the 

 malleus) is a triangular band passing from the posterior part of the notch of Rivinus 

 to the head of the malleus. Helmholtz described the anterior ligament and the 

 posterior part of the lateral ligament as forming together the axis ligament around 

 which the malleus rotates. 



The posterior ligament of the incus (lig. incudis posterius) is a short, thick band 

 connecting the end of the short crus of the incus to the fossa incudis. 





