Paracortex, wool

The arrangement of ortho- and paracortical cells differs among wool types. For example, in lincoln wool an annular (orthocortical core surrounded by paracortex) cellular arrangement is present. Merino fibers possess a characteristic crimp and in these fibers the orthocortex is located on the outer side of the crimp curvature. 

Parachlorobenzotrifluoride, 6 1341 Paracortex, in wool fibers, 22 173 Para-crystalline lattice model, 24 464 Paracyclophane synthesis, 24 38 PARAFAC (PARAllel FACtor analysis),... 

Amino add Epicuticlo Paracortex + Epiouticle Heavy cortical cells Light cortical cells Cuticle Original Merino Merino 64 s 64 s wool wool ... 

Most wool fibers contain two or even three types of cortical cells that are sometimes segregated into two distinct regions (Figure 1-29) that can be readily observed in cross section [82]. These cell types are called orthocortex, paracortex, and mesocortex. Orthocortical cells contain less matrix between the intermediate filaments and a lower sulfur content ( 3%) para-cortical cells are smaller in diameter, and they have smooth and rounded borders and a high sulfur content (-5%) [83]. 

Figure 1-29. Schematic of a wool fiber, illustrating orthocortex and paracortex regions of the cortex in relation to crimp.

The wood fiber has a scaly structure (Figures 30-4 and 38-11). It consists of two parts of differing chemical composition and different properties—the paracortex and the orthocortex. Consequently, the wool fiber is, technologically, a bicomponent fiber (see Chapter 38). The cortices are, in turn, made up of bundles of cortex cells which have a cell nucleus at the center. Each cortex cell consists of microfibrils which are arranged about a core in what is known as a matrix of very sulfur-rich proteins. Each microfibril has 11 of what are called protofibrils, nine of which surround a central pair. Each protofibril consists of two to three a helices. 

Figure 30-4. Schematic representation of the structure of wool fibers W (left) which consist of cortex cells C (center), which, in turn, consist of microfibrils M (right). The microfibrils each contain 11 protofibrils P, each of which is made up of 3 or helices, para, paracortex ortho, ortho cortex.

Except for a small amount of the amino acid methionine, the sulfur in wool occurs in the form of the amino acid cystine. Only approximately 82% of clean wool consists of keratinous proteins, which are characterized by a high concentration of cystine. Approximately 17% of the fiber is protein material of relatively low cystine content (<3%) this has been termed nonkeratinous. As a result of the lower cystine content, the nonkeratinous proteins have a lower concentration of disulfide cross-links compared with the keratinous proteins in the fiber. The nonkeratinous material is, therefore, more labile and less resistant to chemical attack than the keratinous proteins. The nonkeratinous proteins are located primarily in the cell membrane complex between the cortical cells and in the endocuticle (Fig. 3). Approximately 13% of the total nonkeratinous material is also located within the cortical cells, where its distribution differs between the cells of the ortho- and paracortex. 

Merino wool fiber, showing the cuticle, macrofibril (M) in the orthocortex (0) and densely stained nuclear remnant (nr) regions in the paracortex (P). Exocuticle (Ex), endocuticle (En) and cell membrane complex (cm) are clearly differentiated. 

MMA-grafted fiber (Merino wool), showing the appearance of the boundary region of the orthocortex (0) and paracortex (P), It can be seen that the pol5nner occurs homogeneously in various degrees in the para-type cells. 

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