Collagen fiber arrangements

Descemet s membrane is the basement membrane of the endothelial cells. It is comprised of collagen fibers arranged in a hexagonal pattern and embedded in a matrix. 

Table 3.3 Collagen fiber arrangements in some tissues...

As another extracellular component in the cornea, the Bowman s layer is an acellular and amorphous band between the corneal epithelium and stroma. The layer is about 8-12 [im thick and consists of randomly arranged collagen fibers (types I and III) and proteoglycans. The physiological function of Bowman s layer is not yet completely understood, since not all animal species exhibit this membrane in the corneal structures, but an important role in the maintenance of the corneal epithelial structure is expected or probable, since a damaged Bowman s membrane usually results in scarring during wound repair [16],... 

Histologically, the silicotic nodule consists of a relatively acellular, avascular core of hyalinized reticulin fibers arranged concentrically and blending with collagen fibers toward the periphery, which has well-defined borders. ... 

Connective tissues made of collagen and elastic fibers, and blood vessels Smooth muscle fibers arranged in an outer longitudinal layer and an inner circular layer... 

Sclera The sclera is the outermost firm coat of the eye that serves as a protective barrier for the sensitive inner parts. It is composed of the same type of collagen fibers as the corneal stroma. However, the fibers are arranged in an irregular network rather than a lattice pattern, which makes the tissue appear opaque compared to the transparent cornea. The white sclera constitutes the posterior five-sixths of the globe, whereas the transparent cornea comprises the anterior one-sixth [17],... 

Bowman s layer is a thin homogeneous sheet of acellular randomly arranged collagen fibers lying between the epithelial basement membrane and the stroma. Bowman s layer is relatively tough and provides substantial resistance to corneal injury or infection. Because it cannot regenerate, scarring results when it is disrupted. 

The stroma constitutes approximately 90% of the total corneal thickness and is primarily composed of collagen fibers, keratocytes, and glycosaminoglycans. The imiform arrangement of the collagen fibers is the major determinant of corneal transparency, in contrast to the opaque and less regularly arranged fibers of the sclera. Disruption of the stromal layer regularity results in loss of corneal transparency and potential scar formation. 

The feature of traumatized animal cornea treated by CMS was almost normal recovery of most of the peripheral zone structure, which demonstrated the intensification of regeneration processes. Anisomorphy of epithelial regenerate was evidently expressed in the vertical state its surface was smooth. Collagenic fibers and their fascicles were arranged in order cornea itself was without chemosis. Newly formed tissue structure of central trauma sites was less differentiated than that of peripheral ones. In this case, epithelium and regenerated cornea itself (in comparison to control) had a more regulated stmcture. 

On contact with the papillary dermis, phenol destroys the entire elastotic layer within it. Thereafter, the architecture of the dermis is spectacularly restored. Immediately underneath the basal membrane, in the Grenz zone, a dense new layer of collagen fibers is formed, arranged parallel to the... 

Papillary dermis here the fibroblasts are small and have horizontal dendritic processes each fibroblast is in contact with several collagen fibers. These observations explain the dense horizontal arrangement of the new collagen in the papillary dermis after a phenol peel. 

The kidney contains small amounts of fibrillar collagen, but its major collagen is a non-fibrillar network collagen (type IV), a part of basal laminas called the lamina densa (Sect. 5.1.1). Basal laminas are especially well developed in the kidney as exemplified in the glomerulus (Fig. 3.2). The collagen contents of various tissues are indicated in Table 3.2 and their fiber arrangements in Table 3.3. 

Fresh bone - apatite crystallites arranged parallel to collagen fibers, with intercrystalline spaces. 

The last word has probably not been written about the complex optical properties of collagen. The situation is undoubtedly so difficult that it will be clarified only after more detailed models for fibril structure appear from other directions. At the moment one should conclude from the optical studies that in collagen fibers there are oriented long particles (fibrils), that within these are also regularly arranged thinner elements (protofibrils or molecular chains), and that the particles are penetrable in optically indeterminable ways by chemical agents whose molecules can be of some size. 

---