294 



THE ARTICULATIONS, OR JOINTS 



Movements. The movements which take place between the sacrum and coccyx, and between 

 the different pieces of the latter bone, are forward and backivard, and are very limited. Their 

 extent increases during pregnancy. 



Hyaline cartilage covering bone. 



Interpubic disk. 

 Cavity at tipper 

 and back part. ' 



4. ARTICULATION OF THE PUBIC BONES (SYMPHYSIS OSSIUM PUBIS) 



(Figs. 238, 242). 



The articulation between the pubic bones is an amphiarthrodial joint, formed 

 by the apposition of the two oval articular surfaces of the pubic bones. The 

 ligaments of this articulation are the 



Anterior Pubic. Superior Pubic. 



Posterior Pubic. Inferior Pubic. 



Interpubic Disk. 



The anterior pubic ligament (ligamentum pubicum anterius) (Fig. 238) con- 

 sists of several superimposed layers which pass across the front of the articula- 

 tion. The superficial fibres pass obliquely from one bone to the other, decussating 



and forming an interlacement with 

 the fibres of the aponeurosis of the 

 External oblique and the tendon of 

 the Rectus abdominis muscles. The 

 deep fibres pass transversely across the 

 symphysis, and are blended with the 

 interpubic disk. 



The posterior pubic ligament (liga- 

 mentum pubicum posterius) consists 

 of a few thin, scattered fibres which 

 unite the two pubic bones posteriorly. 

 The superior pubic ligament (liga- 

 mentum pubicum superius) (Fig. 238) 

 is a band of fibres which connects 

 the two pubic bones superiorly. 



The inferior pubic or subpubic 

 ligament (ligamentum arcuatum pubis) 

 (Fig. 238) is a thick, triangular arch 

 of ligamentous fibres, connecting the 

 two pubic bones below and forming the upper boundary of the pubic arch. 

 Above, it is blended with the articular disk; laterally it is united with the descend- 

 ing rami of the pubis. Its fibres are closely connected and have an arched 

 direction. Its lower margin is separated from the triangular ligament of the 

 perineum by a gap, through which runs the dorsal vein of the penis. 



The interpubic disk (lamina fibrocartilaginea interpubica) (Fig. 242) consists 

 of a disk of fibrocartilage connecting the surfaces of the pubic bones in front. 

 Each of the two surfaces is covered by a thin layer of hyaline cartilage which is 

 firmly connected to the bone by a series of nipple-like processes which accurately 

 fit within corresponding depressions on the osseous surfaces. These apposed 

 cartilaginous surfaces are connected by an intermediate stratum of fibrous 

 tissue and fibrocartilage which varies in thickness in different subjects. It 

 often contains a cavity (cavum ariiculare] in its centre, probably formed by 

 the softening and absorption of the fibrocartilage, since it rarely appears before 

 the tenth year of life, and is not lined by synovial membrane. It is larger in the 

 female than in the male. It is most frequently limited to the upper and back 



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FIG. 242. Vertical section of the symphysis pubis. 

 Made near its posterior surface. 



