

CARTILAGE 



281 



traced in the adult over a small part of its circumference, and here the cartilage 

 cells are more -or less branched and pass insensibly into the branched connective 

 tissue corpuscles of the synovial membrane. Articular cartilage forms a thin 

 incrustation upon the joint surfaces of the bones, and its elasticity enables it to 

 break the force of concussions, while its smoothness affords ease and freedom of 

 movement. It varies in thickness according to the shape of the articular surface 

 on which it lies; where this is convex the cartilage is thickest at the center, the 

 reverse being the case on concave articular surfaces. It appears to derive its 

 nutriment partly from the vessels of the neighboring synovial membrane and 

 partly from those of the bone upon which it is implanted. Toynbee has shown 

 that the minute vessels of the cancellous tissue as they approach the articular 

 lamella dilate and form arches, and then return into the substance of the bone. 



In Costal Cartilage the cells and nuclei are large, and the matrix has a tendency 

 to fibrous striation, especially in old age (Fig. 294). In the thickest parts of the 

 costal cartilages a few large vascular channels may be detected. This appears, 

 at first sight, to be an exception to the statement that cartilage is a non-vascular 

 tissue, but is not so really, for the vessels give no branches to the cartilage sub- 

 stance itself, and the channels may rather be looked upon as involutions of the 

 perichondrium. The xiphoid process and the cartilages of the nose, larynx, and 

 trachea (except the epiglottis and corniculate cartilages of the larynx, which are 

 composed of elastic fibrocartilage) resemble the costal cartilages in microscopic 

 characteristics. The arytenoid cartilage of the larynx shows a transition from 

 hyaline cartilage at its base to elastic cartilage at the apex. 



The hyaline cartilages, especially in adult and advanced life, are prone to calcify 

 that is to say, to have their matrix permeated by calcium salts without any 

 appearance of true bone. The process of calcification occurs frequently, in such 

 cartilages as those of the trachea and in the costal cartilages, where it may be 

 succeeded by conversion into true bone. 



White Fibrocartilage. White fibrocartilage consists of a mixture of white fibrous 

 tissue and cartilaginous tissue in various proportions; to the former of these con' 

 stituents it owes its flexibility and 

 toughness, and to the latter its 

 elasticity. When examined under 

 the microscope it is found to be 

 made up of fibrous connective 

 tissue arranged in bundles, with 

 cartilage cells between the bundles; 

 the cells to a certain extent re- 

 semble tendon cells, but may be 

 distinguished from them by being 

 surrounded by a concentrically 

 striated area of cartilage matrix 

 and by being less flattened (Fig. 

 295) . The white fibrocartilages ad- 

 mit of arrangement into four 

 groups interarticular, connecting, 

 circumferential, and stratiform. 



1. The Interarticular Fibrocartilages (menisci) are flattened fibrocartilaginous 

 plates, of a round, oval, triangular, or sickle-like form, interposed between the 

 articular cartilages of certain joints. They are free on both surfaces, usually 

 thinner toward the center than at the circumference, and held in position by the 

 attachment of their margins and extremities to the surrounding ligaments. The 

 synovial membranes of the joints are prolonged over them. They are found 

 in the temporomandibular, sternoclavicular, acromioclavicular, wrist, and knee 



Fia. 295. White fibrocartilage from an intervertebral 

 fibrocartilage. 



