9 8 



HISTOLOGY 



It may cover the end of the bone, coming between it and the joint cavity; 

 thus the distal articular surface of the radius is covered with dense fibrous 

 tissue. In other joints, as in the shoulder and hip, such tissue forms a 

 rim, deepening the socket of the joint. These rims are called labra 

 glenoidalia. Large folds or plates of dense fibrous tissue may project 

 into the joint, covered by the synovial layer, thus forming the menisci 

 of the knee joint, and the articular discs such as are interposed inthesterno- 

 clavicular and mandibular joints. Nerves and vessels are absent from 

 the articular cartilages of the adult, and also from the labra and articular 

 discs. 



Hyaline 



cartilage. 



FIG. 86. VERTICAL SECTION THROUGH THE 

 HEAD OF A METACARPAL OF AN ADULT MAN. 

 X 50. 



FIG. 87. SYNOVIAL VILLI WITH 

 BLOOD VESSELS FROM A HUMAN 

 KNEE JOINT. X so. 



The epithelium has fallen from the 

 apex of the left yillus, exposing 

 the connective tissue. 



The synovial layer consists of loose connective tissue, generally with 

 abundant elastic elements. In many places it contains considerable 

 quantities of fat. It has nerves which may terminate in lamellar cor- 

 puscles, numerous blood vessels, and lymphatic vessels which may extend 

 close to the epithelium. The "epithelium" is a smooth glossy layer of 

 connective tissue with parallel fibers and small round or stellate cells 

 containing large nuclei. The cells are sometimes infrequent, as in places 

 where there is unusual pressure. Elsewhere they may be spread in a 

 single thin layer, or heaped together, making an epithelium of three or 

 four strata. The synovial membrane may be thrown into coarse folds 

 (plied) or into slender almost microscopic projections (villi}. The latter 

 impart a velvety appearance to the membrane on which they occur. 



