ARTICULATIONS. LIGAMENTS. 



1 . WJiat is an articulation ? 



Union of bone to bone, bone to cartilage, or cartilage to cartilage, by means of 

 modified periosteum called ligaments. 



2. What are some of the ends subserved by articulations / 



Stability, as in the joints of the cranium ; motility, as in the extremities ; 

 semistability, as in the pelvis and vertebral column. 



3 . Name and indicate the function of the structures found in a typical articula- 

 tion for motility. 



(i) There is bone for strength and solidity ; (2) a shell or covering of bone, 

 free from vessels and nerves, adapted to bear pressure ; (3) a highly polished 

 articular cartilage to confer elasticity and reduce friction ; (4) a capsular ligament, 

 of periosteal derivation, attached above and below the joint to the bones party to 

 the articulation ; (5) a synovial membrane, with its articular vessels and nerves, 

 closely investing the interior of the capsule, for the secretion of synovia. 



4. Name the structures found in an articulation intended for stability. 



Bones with variously shaped edges, whose union in the very young is legal- 

 ized by periosteum called sutural ligament. 



5. Name structures found in an articulation wlicrc semistability is to be attained. 

 Bony surfaces firmly united by discs of cartilage, which admit of slight 



motion, and under certain physiological conditions as pregnancy develop par- 

 tial synovial membrane. 



6. Are there any technical terms by zvhich tlie artiadations, as above classed, are 

 designated / 



SVNARTHROSIS includes all immovable articulations where bone is joined to 

 bone by variously shaped borders, as toothed, grooved, scaled, sawlike, and seam- 

 like. 



AMPHIARTHROSIS includes all articulations in which bone is firmly united to 

 bone by cartilage, with slight movement, as in the pelvis and vertebral column, 

 and a spasmodic production of synovia, as the case may require ; as in pregnancy, 

 this may be the case. 



DIARTHROSIS includes all articulations with perfect capsules, free movement, 

 and constant production of synovia. 



7. Does the degree of motion vary in articulations ? 



Yes ; and the following subdivisions of the class diarthrosis express the 

 variety or kind of movement, in accordance principally with the degree of motion, 

 as determine'd by the shape of the articular surfaces : (i) Enarthrosis, or ball- 

 and-socket variety, in which there is movement in four modified angular direc- 

 tions. Examples of this are seen in the hip, shoulder, and carpo-metacarpal 

 articulation of the thumb. (2) Condylarthrosis, in which free movement, as in the 

 ball-and-socket articulation, is inhibited. Instance, the temporo-maxillary, occi- 

 pito-atlantal, radio-carpal, metacarpo-phalangeal, and metatarso-phalangeal joints. 

 In each, as you may demonstrate on yourselves, there is free movement as 

 flexion and extension in two directions, but very limited movement from side 



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