Collagen fibrils fibril surfaces

Fig. 1.6 (A and B) Scanning electron micro- implantation in the bone marrow showing for-graphs of the porous hydroxyapatite-collagen mation of new bone (white asterisk) attached nanocomposite scaffolds at different magnifi- directly to the nanocomposite (asterisk). Arrows cations. Arrowheads in B indicate the hydroxy- indicate cuboidal osteoblasts on the surface of apatite nanocrystals on the collagen fibrils. new bone. Adapted from [94], reproduced by Histology at (C) 1 week and (D) 4 weeks after permission of Wiley-VCH.

Fibril-associated collagens Types IX and XII bind to the surface of collagen fibrils, linking these fibrils to one another and to other components in the extracellular matrix (see Figure 4.2). 

The distribution of minor collagen types as surface molecules is more obvious for some types than others. Fibril-forming collagens—especially... 

Raspanti, M., Alessandrini, A., Gobbi, P., and Ruggeri, A. (1996). Collagen fibril surface TMAFM, FEG-SEM and freeze-etching observations. Microscopy Res. Tech. 35, 87-93. 

The outer surface of the cornea is covered with a smooth layer of stratified corneal epithelium (Figure 3.4). The lower layer of cells is columnar in shape and rests on a basement membrane that sits on top of a thick limiting structure termed Bowman s membrane derived from the corneal stroma below. The corneal stroma is composed of parallel bundles of collagen fibrils termed lamellae and rows or layers of branching corneal fibroblasts termed keratocytes. The posterior of the cornea is covered with a low cuboidal epithelium with a wide basement membrane (Descemet s membrane) and rests on the posterior portion of the corneal stroma. The corneal epithelium is normally under tension due to the pressure that is present in the anterior chamber just behind the cornea. The intraocular pressure is between 10 and 20 mm of mercury and is enough to cause the cornea to contract about 5% when it is excised from the eye. Therefore this pressure must be transferred between epithelium via cell-cell junctions. 

Figure 3.24. Diagram of the collagen fibrils in cartilage, collagen fibrils in cartilage are composed of a core of types XI and II collagen with zone type IX on the surface. Collagen fibrils are connected to each other and to the cell surface by proteoglycans.

The chondrocytes of the intermediate zone are more spherical than, and differ from, the cells of the superficial layer, which show surface polaritity. Chondrons are found in the intermediate layer. They consist of chondrocytes, pericellular matrix, and pericellular capsule. In this zone, the chondrocytes do not form vertical columns as extensively as is observed in the deep zone. At high magnification the collagen fibrils have a beaded appearance, which may reflect the high level of PGs seen in this region. 

---