Articular cartilage figure

Since hydrogen peroxide generated within the mitochondria of chondrocytes can freely permeate through the chondrocyte cell wall, one should admit the presence of in nil (deep, middle, and superficial) zones of the articular cartilage (Figure 4). The higher the tension, the greater is the content of H Oj and vice-versa. 

Figure 48-6. Dark field electron micrograph of a proteoglycan aggregate in which the proteoglycan subunits and filamentous backbone are particularly well extended. (Reproduced, with permission, from Rosenberg L, Heilman W, Kleinschmidt AK Electron microscopic studies of proteoglycan aggregates from bovine articular cartilage. J Biol Chem 1975 250 1877.)...

Figure 4-16 (A) Dark field electron micrograph of a proteoglycan aggregate from bovine articular cartilage (from bearing surfaces of joints). Courtesy of Joseph A. Buckwalter. The filamentous backbone consists of hyaluronic acid, as in (B). The proteoglycan subunits extend from the backbone. From Rosenberg.149...

Figure 11.9 Schematic of articular cartilage structure showing the superficial, middle and deep zones, the tidemark boundary between the noncalcified and calcified cartilage layer, and the subchondral bone that underlies the articular cartilage.

Figure 11.11 (a) Data from control and collagenase-treated bovine articular cartilage sections. The... 

Figure 1. Articular cartilage is partitioned in three phases, one solid phase and two fluid phases. Each fluid phase contains several species. Some of these species are exchangeable, at least partially water and ions can enter and leave the intrafibrillar space defined by collagen fibrils. Proteoglycans which are macromolecules are too large to be admitted into that space, at least in absence of osteo-arthritis. Water and ions can also be exchanged between the extrafibrillar phase and the exterior.

Figure 3.23. Diagram illustrating the zonal structure of articular cartilage. The superficial zone contains aligned collagen fibrils the intermediate zone contains unoriented collagen fibrils the deep zone contains collagen fibrils perperdicular to the subchondral bone.

Figure 3.27. Diagram illustrating split line pattern in articular cartilage. Collagen fibrils are oriented approximately parallel to the split lines in cartilage.

Figure 7.12. Elastic and viscous stress-strain curves for normal articular cartilage. Elastic (top) and viscous (bottom) stress-strain curves were obtained by plotting the equilibrium (elastic) and the total-equilibrium (viscous) stresses for visibly normal cartilage.

Figure 9.6. Diagram illustrating the pretension present in the superficial zone of articular cartilage. Normal articular cartilage shown at the top is loaded in tension across the surface like a drumhead that is pulled taut over a drum. When a piece of cartilage is cut from the surface, it curls as a result of release of this tension, as shown in the lower diagram. The presence of tension in the superficial zone makes articular cartilage behave like a drumhead, allowing compressive forces applied to the surface at specific points to be distributed across the surface to lower local stresses. The presence of tension on the chondrocytes in the superficial layer may be important to limit inflammation and support reparative processes by stimulating mechanochemical transduction.

Figure 3 is a photograph of a stained joint. The osmarin used in this case contained 35% osmium as a dry solid. All surfaces within the synovial space were stained, articular cartilage on the joint surfaces and the joint capsule which encloses the space. The most proximal lympth node was stained (not shown). 

An interesting secondary finding was made in the experiment in which one month separated injection and sacrifice of the animal. In these cases, the stained articular surface was marked with a lacework pattern of unstained cartilage (Figure... 

Figure 5. A section of the articular cartilage from a pig injected 30 d previously with osmarin. The surface zone (length of double-headed arrow) shows dense staining with toluidine blue to a depth of about 0.1 mm. Chrondrocyte nests (arrows) usually display one or two cells on the surface and one to ten cells in the deeper zones. At the right is a region that corresponds to a white line (arc) seen in Figure 3, Surface staining is not apparent at the white line region.

Figure 6. Articular cartilage taken from a region less than 2 mm from an arthritic lesion. The surface is not differentially stained as shown in Figure 5. Chrondrocyte nests (arrows) contain from one to eight cells and suggest active growth in this region.

Figure 1.5 Proposed mechanism of cartilage degradation during rheumatic diseases Neutrophils invade from the blood flow into the joint space. Upon stimulation they release different ROS and proteolytic enzymes. These damage-conferring products lead to the degradation of the high-mass components of articular cartilage under the formation of low-mass components. Reprinted with permission from [98].

Tamai et al., 1988]. The radius of curvature of a circle fitted to the entire proximal phalanx surface ranges from 11 to 13 mm, almost twice as much as that of the metacarpal head, which ranges from 6 to 7 mm (Table 49.20). The local centers of curvature along the sagittal contour of the metacarpal heads are not fixed. The locus of the center of curvature for the subchondral bony contour approximates the locus of the center for the acute curve of an ellipse (Figure 49.29). However, the locus of center of curvature for the articular cartilage contour approximates the locus of the obtuse curve of an ellipse. 

FIGURE 49.29 The loci of the local centers of curvature for subchondral bony contour of the metacarpal head approximates the loci of the center for the acute curve of an ellipse. The loci of the local center of curvature for articular cartilage contour of the metacarpal head approximates the loci of the bony center of the obtuse curve of an ellipse. (From Tamai K., Ryu J., An K.N., Linscheid R.L, Cooney W.P., and Chao E.Y.S. 1988. J. Hand Surg. 13A 521. Reprinted with permission of Churchill Livingstone.)... 

Figure 23 Model of the structure-function relation of the bone/articular cartilage interface. Schematic of part of a joint containing bone covered by articular cartilage. The dominant fibrii orientation in the cartilage is indicated, as well as the mineral particle orientation in bone. Reproduced from Zizak, i. Roschger, P. Paris, 0. etal. J. Struct. Biol. 2003, 141,...

Osteoarthritis (OA) affects the articular cartilage and imderlying bones at the joint. Primary OA is associated with progressive wearing of e humeral head and the posterior aspect of the glenoid (Figure 9.2) (Hill and Norris 2001, Hayes... 

The articular cartilage is an avascular, acidic (pH 6.6-6.9) and lyperosmotic tissue dependent on diffusion of nutrients supplied mainly from SF (and perhaps partly from subchondral bone [14]) to provide for the metaboUc requirements of chondrocytes. The oxygen levels in this tissue are low, ranging between 1 and 6% (cf. Figure 4). While reduction in 02 tension to 6% in all other tissues is already lypoxic, for chondrocytes such oxygen level is normoxic. 

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