ARTHROLOGY 



An articulation or joint is the connection between two or more 

 parts of the skeleton in the recent condition. In most joints the 

 parts are osseous, but in certain cases cartilage forms the basis. 

 The manner in which the parts are connected and the amoimt of 

 movement allowed between them vary, and joints are accordingly 

 divided into three classes, namely, synarthrosis, amphiarthrosis, 

 and diarthrosis. 



Synarthrosis. — This is direct union, there being only a small 

 amount of intervening tissue without any joint cavity, and the joint 

 is immovable. There are two varieties of this class — s3mchondrosis 

 and suture. 



1. Synchondrosis. — In this joint a thin plate of hyaline cartilage 

 intervenes between the component parts, as, for example, between 

 the diaphysis or shaft and epiphyses of a long bone. It is essentially 

 a temporary joint. 



2. Suture. — In this variety the bones are separated by a 

 small amount of fibrous tissue, which is continuous with the peri- 

 osteiun. Such joints are only met with in the skull. There are 

 three forms of suture, called true, false, and grooved. When the 

 margins of the bones present a number of projections with inter- 

 vening depressions, so that they become closely interlocked, the 

 suture is called true. WTien the opposed margins are more or less 

 flat, so that there is merely apposition without interlocking, the 

 suture is spoken of as false \\^en one margin presents a ridge and 

 the other a cleft into which the ridge is received, it is known as a 

 grooved suture. 



True sutures are of three kinds— serrated, dentated, and limbous. 

 In the serrated suture the margins of the bones are saw-like, as in 

 the frontal suture ; in the dentated suture the margins present 

 projections like teeth, as in the interparietal suture ; and in the 

 limbous suture the margins of the bones are ridged and bevelled 

 so that they overlap, as in the lower and mesial parts of the fronto- 

 parietal suture. 



False sutures are of two kinds — squamous and harmonic. In the 

 squamous suture the margins are bevelled so that one overlaps the 

 other, as in the squamo-parietal suture. In the harmonic suture 

 the surfaces, which are rough, are in direct apposition, as between 



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