264 THE ARTICULATIONS, OR JOINTS 



it is termed a true suture, orsutura vera, of which there are three varieties sutura 

 dentata, serrata, and limbosa. The sutura dentata is so called from the tooth-like 

 form of the projecting articular processes, as in the suture between the parietal 

 bones. In the sutura serrata the edges of the two bones forming the articulation 

 are serrated like the teeth of a fine saw, as between the two portions of the frontal 

 bone. In the sutura limbosa besides the dentated processes, there is a certain 

 degree of bevelling of the articular surfaces, so that the bones overlap each other, 

 as in the suture between the parietal and frontal bones. When the articulation 

 is formed by roughened surfaces placed in apposition with one another, it is 

 termed the false suture, of which there are two kinds the sutura squamosa, formed 

 by the overlapping of two contiguous bones by broad bevelled margins, as in the 

 squamoparietal (squamous) suture; and the sutura harmonia, where there is simple 

 apposition of two contiguous, rough, bony surfaces, as in the articulation between 

 the two maxillae or of the horizontal plates of the palate bones. 



Schindylesis is that form of articulation in which a thin plate of bone is 

 received into a cleft or fissure formed by the separation of two laminae in another 

 bone, as in the articulation of the rostrum of the sphenoid and perpendicular 

 plate of the ethmoid with the vomer, or in the reception of the latter in the fissure 

 between the maxillae and palate bones. 



A gomphosis is an articulation formed by the insertion of a conical process 

 into a socket, as a nail is driven into a board; this is not illustrated by any articu- 

 lation between bones, properly so called, but is seen in the articulation of the teeth 

 with the alveoli of the maxillae and mandible. 



A synchondrosis is a joint in which the connecting medium is hyaline cartilage. 

 This is a temporary form of joint, because the hyaline cartilage becomes con- 

 verted into bone before adult life. Such joints are found between the epiphyses 

 and shafts of long bones, between the occipital and the sphenoid at, and for some 

 years after, birth, and between the petrous portion of the temporal and the 

 jugular process of the occipital. 



Amphiarthrosis (Mixed Articulation). In the amphiarthrosis there is only 

 a slight amount of motion. Two varieties of this form of joint are recognized: 

 A symphysis is that joint in which the contiguous osseous surfaces are connected 

 by a broad flattened disk of fibrocartilage which is attached to both bases as 

 in the articulation between the bodies of two vertebrae and between the two pubic 

 bones. A partial joint cavity and an incomplete synovial membrane may be 

 found in such joints. 



A syndesmosis is an amphiarthrodial joint in which the bony surfaces are 

 joined by an interosseous ligament, as in the inferior tibiofibular articulation. 



Diarthrosis (Movable Articulation) . This form of articulation includes the 

 greater number of the joints in the body, mobility being their distinguishing 

 character. They are formed by the approximation of two contiguous bony 

 surfaces covered with cartilage, connected by ligaments and lined with synovial 

 membrane. The varieties of joints in this class have been determined by the 

 kind of motion permitted in each. There are two varieties in which the move- 

 ment is uniaxial; that is to say, all movements take place around one axis. In 

 one form, the ginglymus, or hinge-joint, this axis is, practically speaking, trans- 

 verse; in the other, the trochoid, or pivot-joint, it is longitudinal. There are two 

 varieties where the movement is biaxial or around two horizontal axes at right 

 angles to each other or at any intervening axis between the two. These are the 

 condyloid joint and the saddle-joint. There is one form of joint where the move- 

 ment is polyaxial, the enarthrosis, or ball-and-socket joint. And finally there are 

 the arthrodia, or gliding joints. In a diarthrosis there is always a joint cavity 

 lined with synovial membrane the articular surfaces of the bones are covered 

 with hyaline cartilage, and the bones are held in contact by ligaments. 



