Collagen fibrils/fibres

Hukins, D. W. L., and Woodhead-Galloway, J. (1977). Collagen fibrils as examples of smectic A biological fibres. Mol. Cryst. Liq. Cryst. 41, 33-39. 

The sarcolemma consists of a plasma membrane and an onter coat made np of a thin layer of polysaccharide material that contains numerous thin collagen fibrils. At each end of the muscle fibre this outer coat of the sarcolemma fuses with a tendon fibre, and the tendon fibres in turn collect into bundles to form the muscle tendons that then insert into bones. The membrane is designed to receive and conduct stimuli, is extensible and encloses the contractile substance of a muscle fibre. The sarcolemma is attached to the cytoskeleton on its cytoplasmic surface. It invaginates into the c)doplasm, forming membranous tubules called transverse tubules sarcoplasmic reticulum (enlarged smooth endoplasmic reticulum) lies either side of the transverse tubules. The transverse tubules and sarcoplasmic reticulum transmit altered membrane permeability down the tubules and into the muscle. 

Figure 6.31 AFM Images at different levels of resolution All images are generated with false colour (a) Collagen fibrils (Chapter 1) (b) Cellulose fibres (Chapter 1) (c) plasmid DNA (Chapter 3) (d) DNA...

Tendons have the greatest tensile strength of all connective tissue due to the high collagen content of the fibres, and their closely packed parallel arrangement in the direction of force. Tendons have a hierarchical structure with individual collagen fibrils arranged into fascicles which contain blood vessels and nerve... 

In the human spleen, vinyl chloride-induced lesions were primarily but not a consequence of portal hypertension (Heusermann and Stutte 1977, Stutte and Heusermann 1977). Fibre-associated reticulum cells of the red pulp and fibroblastic reticulum cells in white pulp were stimulated to produce excessive amounts of the extracellular elements of connective tissue, especially collagen fibrils. 

The basic structural unit of skeletal muscle is a muscle fibre composed of long, cylindrical cells of 10-100 xm in diameter and lengths of up to several tens of mm (usually 20-30 mm). Each muscle fibre is actually a muscle cell containing 100-200 nuclei and normal cell organelles. The muscle fibre is covered by a thin, extensible, semi-permeable membrane, the sarcolemma (or myolemma), which transmits electrical impulses from the nerves. It consists of a cell membrane (plasma membrane) and an outer coat made up of a thin layer of polysaccharide material with numerous thin collagen fibrils. The sarcoplasm of a muscle fibre is comparable to the gel-like cytoplasm of other cells. 

Fig. 1 Hierarchical structural oigamzadon of bone (lefi to right) cortical and cancellous bone osteons with Haversian systems lamellae collagen fibre assemblies of collagen fibrils bone mineral crystals, collagen molecules and non-coUagenous proteins. Reprinted from [12] with permission from Elsevier...

The individual collagen ropes are called fibrils, and have an average molecular weight of around 300 000 Daltons (atomic mass units), with a length of 260 nm and a diameter of 1.4-2.0 nm. In the collagen fibres which can be seen... 

Collagen fibres (a) and hydroxyl apatite crystals (b) together form larger units, the so-called micro-fibrils (c). It should be pointed out here that the collagen fibres are helically intertwined and consequently... 

Figure 3.2 Schematics of the hierarchical architecture of cortical bone. (A) Longitudinal section of femur. (B) Enlarged cross section of cortical bone showing cylindrical osteons. (C) Enlargement of an osteon showing the central Haversian canal with a blood vessel, the concentric lamellae and the radial canaliculi (see also J). A more detailed view of an osteon is shown in the inset in the bottom right. (D) Collagen fibre composed of hundreds of fibrils. The evenly spaced dark spirals are...

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