ARTICULATIONS AND LIGAMENTS. 



THE bones of the skeleton are connected together by articu- 

 lations or joints. 



These consist essentially of the expanded extremities of 

 bones, covered with cartilage, often separated by inter articular 

 fibre-cartilage, held together by ligaments, and lined by synovial 

 membrane. 



The bone entering into the articular lamella differs from 

 ordinary bone by its extreme density, without Haversian canals, 

 its lacunae being much larger, and without canaliculi. It is not 

 perforated by blood-veysels. 



Cartilage is a whitish, highly elastic, non-vascular structure, 

 forming in the fcetus the greater part of the skeleton, and found 

 in the adult chiefly in the joints, the walls of the thorax, and 

 certain orifices, as the nostrils, ears, etc. 



It is either temporary, becoming ossified later, or permanent, 

 remaining unossified. The latter is divided into three varieties : 

 articular, in joints covering the ends of the bones ; costal, form- 

 ing part of the thorax; and reticular, arranged in plates or 

 lamellae to maintain the shape of parts. 



Fibro-cartilage consists of a mixture of cartilaginous with 

 white fibrous tissue. There are four varieties : 



(a) Inter articular, interposed between the joint surfaces; 



(b) Connecting, binding bones together as in pubes; 



(c) Circumferential, deepening cavities, as glenoid cavity of 

 shoulder ; and 



(dj Stratiform, lining grooves for tendons. 



Synovial membranes are of three kinds: articular, lining 

 tho cavities of movable joints throughout except the surface of the 

 cartilage; bursal, irregular cavities interposed at convenient posi- 

 tions to alleviate friction; from their contents they may be 

 cither mucous or synovial; and vaginal synovial membranes, or 

 bheaths, surrounding tendons and diminishing friction. 



Synovia is a transparent, viscid liquid, albuminous in its 

 nature. 



The articulations consist of three (3) classes: (li;irtlini-. 

 movable; synarthrosis, immovable; and amphiarthrosis, mixed. 



(Ill) 



