Hair, fiber surface/structure

Fig. 12.7. Scanning electron microscopy reveals details of hair fibers. Normal hairs from an adult C57BL/6J examined as a whole mount (A) illustrates density of mouse hairs and the nature of the normal skin surface. Manually plucked hairs illustrate the structural differences between some of the hair fiber types (B). Higher magnification of boxed area in B reveals the regular cuticular scale patterns on these hair fibers (C). These approaches illustrate details of hair fiber structure and density (80).

On the other hand, the loose feathers identified from Etowah No. 1156 could have been spun at one time, but they come from a mat of fiberlike material on which no yam structures currently are evident. Their juxtaposition with the re-plied yam (perhaps of animal hair) presents an anomaly because descriptions (8,12) of other feather yarns do not include a re-plied yam without a bast core. The yam appears to be alike in all its parts. Its color, texture, and surface smoothness suggest an animal-hair fiber. 

Figures 4-10 to 4-12 show the effects of ultraviolet exposure followed by reaction with alkaline hydrogen peroxide for different times (15 min to 2 h). The effects of the alkaline peroxide on ultraviolet exposed hair are to dissolve parts of the cuticle, providing for even less structural differentiation. Part of the cuticular proteins are solubilized by these combined chemical treatments into gelatin-like glue that is redeposited between the fibers, see Figure 4-11. This effect was produced after only 15 min exposure to alkaline peroxide after photochemical degradation. The total lack of surface structural definition is seen in the most extreme case in Figure 4-12 where no cuticle scale definition exists after 2h of treatment with alkaline hydro-...

Figure 8-34. Scanning electron micrograph of a knotted hair fiber, illnstrating the cnticle cell surface structure. Note the raised scales caused by the severe bending stress of the knotted fiber.

While some of the Mississippian textiles are of similar structure to the Middle Woodland textiles, others are very complex materials and are lace-like in appearance. Many of the materials from Etowah are preserved by mineralization, and display green-colored deposits on their surfaces. Bast fiber, rabbit hair, and feathers have been identified (2, 11). The textiles from these two sites selected for analysis are representative of the complexity of structure and fineness of yarns seen in the materials they provide evidence of the sophisticated technology of prehistoric people in all phases of fiber collection, processing, yarn spinning, fabric manufacture and, when present, coloration. 

Each cotton fiber is a single, elongated, complete cell that develops in the surface layer of cells of the cottonseed. The mature cotton fiber is actually a dead, hollow, dried cell wall [4,5,43], In the dried out fiber, the tubular structure is collapsed and twisted, giving cotton fiber convolutions, which differentiate cotton fibers from all other forms of seed hairs and are partially responsible for many of the unique characteristics of cotton. The biosynthesis and morphology of the cotton fiber are discussed in more detail later (see Chapter 2). 

The Etowah fabric bundle (No. 840) contains fine yarns made of bundles of vegetable fibers typical of bast fibers. The core yams of Etowah Mound C (EMC) No. 1145 also are bast, and they are wrapped with feathers. Figure 10 is an electron micrograph of the nodes on the barbules of these feathers. The copper plate EMC No. 1156 contains a twisted yarn of undetermined fiber composition the fibers are smooth, untwisted, and long. Perhaps they are hair, but no scale structure was apparent on their surfaces. In the same area of the plate, some loose fibrous material adjacent to the yam proved to be feather. In a second area of the plate, some fibrous material of undetermined type similar in appearance to that in the first area is present. 

Animal hairs develop by the proliferation of cells from the germinal layers of the skin in specialized structures known as follicles. As the cells progress up the follicle toward the skin surface three types of cells differentiate and fuse together to give the principal components of the fiber. 

Cotton fibers are single-celled hairs that cover the surface of the cotton seed. They are formed independently and thus contain no intercellular substance (Figure 1). Wood fibers, on the other hand, form a cohesive three-dimensional structure (Figure 2) whose integrity is assured by large amounts of intercellular substance (Figure 3). The outermost layer of cotton is called the cuticle. The equivalent layer in the multicellular structure of wood is the middle lamella. 

Leeder and Rippon [85] have analyzed the lipid composition of wool fibers after removing surface grease. Continued extraction with solvent removed the beta layers evidenced by electron microscopy however, the extract contained free cholesterol and free fatty acid and triglycerides but negligible quantities of phospholipid normally associated with biological membrane lipids. Koch [86], in his work with internal lipid of human hair, did not report significant quantities of phospholipid. These lipid-protein layers of hair are most likely related structurally to those of the epicuticle. 

FIGURE 5.11 Transmission electron micrograph of stained transverse section showing the ultrafine structure of the CMC of apposed fiber cuticle cells in human hair. The CMC comprises two unstained modified membranes (P-layers) and an intercellular 8-layer of higher staining intensity. Note also the internal laminae in the 8-layer with thickness approximately 0.005 p,m. An intracellular membrane associated layer (i) forms a narrow band on the underside of a fiber-cuticle cell. The dark stained band (a) is the surface a-layer of exocuticle (exo) from an underlying cuticle cell. The section was stained with osmium tetroxide, uranyl acetate, and lead citrate after prior reduction with thioglycolic acid. Bar equals 0.1 p.m. 

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