Henry Gray (18251861). Anatomy of the Human Body. 1918.
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 substance 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 calcifythat 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 constituents 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 resemble 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 admit of arrangement into four groupsinterarticular, connecting, circumferential, and stratiform.
FIG. 295 White fibrocartilage from an intervertebral fibrocartilage. (See enlarged image)
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