Cartilage

“ Elastic cartilage is found in the epiglottis and the cartilages of the larynx.
Fibro cartilage is found at the point of insertion of the ligaments, into the body of the bone, such as the cartilage which helps to hold the femur or long bone of the thigh into the hip.
Bones.
—Bone results from the calcification of cartilage or fibrous tissue. It is a highly specialized form of [49] connective tissue. There are two varieties of bone; dense or compact bone and cancellous, loose, or spongy bone. Compact bone is dense, like ivory, and is always found on the exterior of bones. ”

“ Bone consists of earthy salts deposited in a finely granular form throughout the substance of cartilage. By soaking a piece of bone in vinegar or other dilute acid, the earthy salts will be dissolved, the soft cartilage being left. But the structure of cartilage may be best observed by making thin sections of the gristle covering the ends of bones. It exhibits a bluish-white basis (Pl. IX. fig. 16) , in which are imbedded numerous cells or cartilage-corpuscles, often undergoing cell-division. In some kinds of cartilage, the basis is composed of fibres. ”

“ The chief difference in make-up between bone and cartilage is that while in bone about three-fourths of the nonliving substance consists of lime salts, in cartilage there is almost none of this material, organic substances making up the entire mass. There are no living cells in the body that are more poorly located with respect to obtaining supplies from the body fluids than the cartilage cells, for as these deposit the cartilage around themselves they leave no definite passages through which fluid may pass ”

“ The opposing surfaces of the bones are lined with articular cartilage, which is the unossified remnant of the cartilaginous model in which they are formed and is called the cartilage of encrustment (fig. 4, c) . Between the two cartilages is the joint cavity, while surrounding the joint is the capsule (fig. 4, l) , which is formed chiefly by the superficial layers of the original periosteum or perichondrium, but it may be strengthened externally by surrounding fibrous structures, such as the tendons of muscles, which become modified and acquire fresh attachments for the purpose. ”

“ We may perhaps go further and attribute this difference of composition to a difference of origin; for whereas the soft cartilage is invariably formed in a special tissue, the muco-cartilage, which shows by its reaction how largely it is composed of a mucoid substance, the hard cartilage is certainly, in the case of the cartilage of the cranium where its origin has been clearly made out, formed in the membranous tissue of the cranium of Ammocœtes—i.e. in a tissue which stains light blue with thionin, and contains a gelatinous rather than a mucoid substratum. ”

“ Perhaps the best advice we can give is to say that the whole of the cartilage must be manipulated both with the foot on and off the ground. What the reason may be we do not pretend to say, but it is a well-known fact that in many instances the cartilage, with the foot bearing weight, is so rigid as to at once convey the impression that ossification has commenced or is even far advanced. ”

“ When the elastic cartilaginous rib becomes bony, nothing different is happening from that which happened before, for there was a stage of development when the entire rib consisted of cartilage, and in the progress of development toward the adult condition that cartilage was changed gradually into bone, thus producing the characteristic, normal, efficient bony rib of the adult. When old age intervenes, the change of the cartilage into bone goes yet further, but it progresses in such a way that it is no longer favorable, but unfavorable. ”

“ Then at certain points the cartilage begins to be dissolved away by cartilage-destroying cells, which are precisely like bone-destroying cells, and the bone-forming cells come in and build up the real bone as fast as the cartilage is removed. ”

“ A delicate layer of bone, developed in the perichondrium, invests the cartilaginous neural arches, and this bone grows upwards so as to unite above with the osseous investment of separately developed bars of cartilage, which are directed obliquely backwards. These bars, or dorsal processes, may be reckoned as parts of the neural arches. Between the dorsal processes of the two sides is placed a median rod of cartilage, which is developed separately from the true neural arches, and which constitutes the median spinous element of the adult. ”

“ Although entirely different in nature and chemical composition, the cartilage tissue serves to maintain certain outlines of form and feature in the human body, which are not based on the still stronger forms of supporting material, such as the bone tissue and the gelatigenous tissue. ”

“ In parts of the animal which require special support it forms solid rods, the collagen combining with calcium salts to form a clear, hard substance—cartilage. At one period in the development of an animal or animals we find the only solid support is cartilage, but cartilage is not sufficiently rigid for a very large beast, especially on land, so is only used for outlying parts, the main framework being bone. ”

“ One or two sutures may also be taken across the angles of union of the alæ and the flap A. The inferior raw surface of each wing may be found to be too wide, owing to the presence of the thickened cartilage at this point of the wing. The skin and the mucous membrane are then carefully peeled away from the cartilage, and the latter cut away as high as possible, or a gutterlike incision is made along its edges as shown in C (Fig. 485) , excising the elongated elliptical piece of tissue which includes the cartilage. ”

“ By carrying out movements between the constituent parts, the fibrous tissue covering the ends of the bones becomes moulded into shape, its cells take on the characters of cartilage cells, and, forming a matrix, so develop a new cartilage. ”

“ In cases where a membrane bone, as the dermal ossifications are usually called, overlies a part of the cartilage, it may set up ossification in the latter, and the cartilage bone and membrane bone may become so intimately fused as to be quite inseparable. It seems probable that in cases of this kind the compound bone may in the course of further evolution entirely lose either its cartilaginous element or its membranous element; so that cases occasionally occur where the development of a bone ceases to be an absolutely safe guide to its evolution. ”

“ Some are wholly cartilaginous, the disease commencing in their centre, and involving their entire substance, emitting a gelatinous fluid when cut, but containing no cells; others are not uncommon, partly osseous, and partly cartilaginous, containing cells filled with a glairy fluid; others are composed of cartilage, intersected with dense fibrous matter, in a greater or less proportion. In fact, the individual tumours of bones vary as much from one another as those of the softer tissues ”

“ Fibrillation of the cartilage imparts a feeling of roughness when the joint is grasped during flexion and extension, and lipping of the margins of the trochlear surface of the femur may be felt when the joint is flexed; it is also readily seen in skiagrams. When a portion of the “lipping” is broken off, it may give rise to a loose body. In advanced cases with destruction of the cartilages, there may be movement from side to side, with grating of the articular surfaces. ”

“ Cartilage consists of groups of nucleated cells in intercellular substance. It is very firm, yet highly elastic, and serves in the joints to break the force of concussion of the harder and less elastic bones. Except when it occurs at the end of a bone, it is covered with a membrane called the perichondrium, which carries its blood supply. In the nose, ear, larynx and trachea it serves to give shape, to keep the [Pg 17] passages open, and to afford attachment for muscles. Most of the skeleton of the fetus consists of cartilage, which later develops into bone. ”

“ Besides the ordinary kind of cartilage, temporary and permanent, there are two modifications of the tissue, confined to certain portions of the body: cellular cartilage, composed of cells lying close together, in a mesh formed of fine fibres; and fibro-cartilage, cells distributed in a matrix of fibrous tissue.
Examined with a low power, cartilage appears to be homogeneous in structure, studded over with numerous round, oval, oblong, semilunar, and irregular-shaped corpuscles, as seen in Plate XIX., No. ”

“ In movable, or true joints the articular surface of each bone is covered by cartilage. The bones are held together by ligaments, the capsular one often surrounding the joint and enclosing the synovial membrane. In some joints there is a pad of fibrous cartilage interposed between the two articular cartilages. Such a pad, called a meniscus, adds to the elasticity and the free movement of the joint. Movable joints form the most numerous class; they are for the most part found in the limbs. ”

“ In the lower jaw two masses of cartilage are seen, one near the symphysis (mk) and one near the wall of the trachea, doubtless the rudiment of the hyoid. The deep groove back of the Meckel’s cartilage (mk) marks the tip of the developing tongue, which here forms the thick mass on the floor of the mouth cavity. Dorsal to the pharynx a mass of cartilage (se) is developing in the sphenethmoid region. ”

“ The articular cartilage of the head, being no longer in contact with an opposing cartilage, tends in time to be converted into fibrous tissue, and may become adherent to other fibrous structures in its vicinity. By pressing on adjacent structures it may form for itself a new socket of dense fibrous tissue which in time becomes lined with a secreting membrane. ”

“ Further, in fully-grown specimens of Ammocœtes, in the region of undoubted muco-cartilage, a fatty degeneration of the cells frequently appears, together with an increase in the blood spaces,—the precursor, in fact, of the great change which overtakes this tissue soon afterwards, at the time of transformation, when it is invaded by blood, and swept away, except in those places where new cartilage is formed. ”

“ The “collagen,” obtained from tendons and connective tissues, also occurs in the cornea and sclerotic coat of the eye, and in fish scales. Cartilage was considered to be composed of a substance chondrigen, which gave chondrin or cartilage-glue on boiling with water. Recent researches make it probable that cartilage contains (1) chondromucoid, (2) chondroitin-sulphuric acid, (3) collagen, (4) an albumoid present in old but not in young cartilage; whilst chondrin is a mixture of gelatin and mucin. “Bone collagen,” or “ossein,” constitutes, with calcium salts, the ground substance of bones. ”

“ If the distension persists, the ligaments become elongated and the joint unstable.
The common origin of bone, cartilage, periosteum, and synovial layer from one parent tissue of the embryo, accords with the readiness with which any one of these tissues may be converted into another under traumatic or pathological influences; and how in ligaments and in synovial membrane foci of hyaline cartilage may form and, after increasing in size, undergo ossification.
Joints derive an abundant blood supply through the articular arteries. ”

“ It is obvious then that the presence of proper cartilage constituents in the blood is of the greatest importance to the regenerating forces in the human body. Our foodstuffs, therefore, must contain the material in a digestible, assimilable form, thus to prevent inanition of the cells, otherwise degeneration of the cartilage tissue must follow.
(d) . Dose: One gram or one-fourth of a heaping teaspoonful twice a day for a certain period, depending on the condition of the patient. ”

“ The abundant supply of intervertebral cartilage has another important use, namely, it adds greatly to the elasticity of the frame. It is due, in part, to this elastic material, and in part to the frequent curves of the spine, that the brain and other delicate organs are protected from the shock of sudden falls or jars. During the day, the constant pressure upon these joints, while the body is erect, diminishes the thickness of the cartilages; so that a person is not so tall in the evening as in the morning. ”

“ Hyaline cartilage.—Specimens may be obtained from any joint, from the costal cartilages of young animals, or from the thyroid cartilage and tracheal rings. It may be hardened in spirit. Stain with picrocarmine, eosine and hæmatoxyline, and with methyl violet. ”

“ In the very young rabbit, the limb bones, vertebral column, and many of the skull bones are simply plates and bars of cartilage; the future membrane bones, however are planned out in connective tissue. The development of the latter is simple, the connective tissue corpuscles functioning by a simple change of product as osteoblast. The development of the cartilage bones, however, is more complicated. ”

“ We know, however, that with commencing rigidity we may ere long expect one, and if our opinion is asked with regard to that particular, it must be admitted that with rigidity of the cartilage once commenced it is usually not long afterwards before a fully-developed side-bone makes its appearance. ”

“ Hence the vomers of the dog lie, not in the ceiling of the mouth, but in the floor of this nasal passage. Section 31. The quadrate cartilage of the frog is superseded by the squamosal as the suspensorium of the lower jaw. It is greatly reduced, therefore; but it is not entirely absent. In the young mammal, a quadrate cartilage can be traced, connected with the palato-pterygoid cartilage, and articulating with Meckel's cartilage. Its position is, of course, beneath the squamosal, and just outside the otic capsule. ”