Fibrous connective tissue

Estrogens stimulate cellular proliferation, induce RNA and protein synthesis of uterine endometrium and the fibrous connective tissue framework for ovaries, and increase the size of the cells. This effect leads to the growth and regeneration of the endometrial layer and spinal arterioles, and increase in the number and size of endometrial glands. Under the influence of estrogen, vaginal mucosa becomes thicker, as cervical mucus becomes thinner (85,86). 

Tendons are composed of fibrous connective tissue. Tendon tissue is also formed by the fibroblast ceUs, similar to the way ligaments are formed. These fibroblast ceUs then further differentiate into other specialized ceUs known as fibrocytes. Mature fibrocytes are inactive and compose the ceUular portion of tendons. The function of the tendon is to attach muscles to bones and other parts. 

Proteins can be broadly classified into fibrous and globular. Many fibrous proteins serve a stmctural role (11). CC-Keratin has been described. Fibroin, the primary protein in silk, has -sheets packed one on top of another. CoUagen, found in connective tissue, has a triple-hehcal stmcture. Other fibrous proteins have a motile function. Skeletal muscle fibers are made up of thick filaments consisting of the protein myosin, and thin filaments consisting of actin, troponin, and tropomyosin. Muscle contraction is achieved when these filaments sHde past each other. Microtubules and flagellin are proteins responsible for the motion of ciUa and bacterial dageUa. 

Collagen is a rigid, inextensible fibrous protein that is a principal constituent of connective tissue in animals, including tendons, cartilage, bones, teeth, skin, and blood vessels. The high tensile strength of collagen fibers in these struc-... 

The neuromuscular complications of diabetes mellitus are most often neuropathic in origin, with distal sensorimotor polyneuropathies being the most common. In addition, ischemic infarction of skeletal muscle may occur due to occlusive vascular disease, with small and medium-sized arterioles particularly affected. This occurs in poorly-controlled diabetes and affects thigh, muscles in most cases. In acute stages, muscle biopsy findings are those of widespread muscle necrosis, edema, and phagocytic cell infiltration. Muscle regeneration may be incomplete and increased fibrous connective tissue may replace lost muscle tissue. 

Collagen is the most abundant animal protein in the body of animals, where it makes up as much as one-quarter of all the proteins. It is a fibrous protein that provides structure to and protects and supports soft tissues it also connects tissues to the skeleton. Collagen forms, for example, most of the resilient layers that make up the skin and the filaments that support the internal organs. Interwoven with bioinorganic components, collagen also makes up the bones and teeth of vertebrate animals (see Chapter 15). 

Histopathological changes were noted in the kidneys of rats administered lead acetate in the drinking water for 76 weeks at lower doses (Roller et al. 1985). These changes, which were observed at a dose of 37 mg/kg/day, a dose much lower than that used by Vyskocil et al. (1989), included necrotic and dilated cortical tubules, tubular protein casts, areas with large nuclei and fibrous connective tissue, and large intranuclear inclusion bodies in the enlarged epithelial cells of the cortex near the cortical-medullary junction. 

An internodal conduction pathway also extends from the SA node and transmits the impulse directly to the atrioventricular (AV) node. This node is located at the base of the right atrium near the interventricular septum, which is the wall of myocardium separating the two ventricles. Because the atria and ventricles are separated from each other by fibrous connective tissue, the electrical impulse cannot spread directly to the ventricles. Instead, the AV node serves as the only pathway through which the impulse can be transmitted to the ventricles. The speed of conduction through the AV node is slowed, resulting in a slight delay (0.1 sec). The cause of this AV nodal delay is partly due to the smaller fibers of the AV node. More importantly, however, fewer gap junctions exist between the cells of the node, which... 

Fibrosis Any pathological condition where fibrous connective tissue invades any organ, usually as a consequence of inflammation or other injury. [NIH]... 

The fibrous protein elastin found extensively in connective tissues is unlike collagen in that it occurs in a less well ordered fashion, furthermore, there are quite marked differences seen between the chemical compositions of collagen and elastin. Whereas collagen comprises a very limited number of different amino acids, elastin contains a wider variety, the most abundant being glycine (approximately 30% dry weight), alanine (23%) valine (15%) and proline (12%). 

Figure 1.10 Columnar and stratified epithelia. Epithelial b ssues are underlain by a basement membrane which is a composite structure composed of an amorphous basal lamina, secreted by the epithelial cells, and a more fibrous reticular lamina derived from connective tissue.

The interactions of these cells with T lymphocytes also in the lesion and the overlying endothelium can lead to a massive flbroproliferative response over which connective tissue from smooth muscle cells form a fibrous cap. This covers the advanced lesion or fibrous plaque of atherosclerosis, deeper portions of which consist of macrophages, T lymphocytes, smooth muscle cells, connective tissue, necrotic debris and varying amounts of lipids and lipoproteins. 

The pleural tissue is a typical connective tissue that consists mostly of matrix the fibrous proteins (collagen, elastin), and mucopolysaccharides, and a few scattered mesothelial cells, capillaries, venules, and ducts. Anatomists have defined several layers (Fig. 3.4) for each of the pleura. Layers 3 and 5 in Fig. 3.4 contain an abundance of fibrous protein, especially elastin. Both the interstitial (Layer 4) and mesothelial (1 and 2) layers contain capillaries of the vascular system and lymphatic channels. The matrix (ground substance) gives the pleura structural integrity and is responsible for its mechanical properties such as elasticity and distensibility. 

Orotic acid or 6-methyluracil vide infra), when administered to rabbits with myocardial infarction induced by ligation of the anterior descending branch of the left coronary artery, can decrease the incidence of necrosis and increase the rate of regeneration for healthy cellular and fibrous connective tissue in the infarct region [182]. Rats with induced aortal stenosis which are treated with... 

Collagen, a class of fibrous protein, is the most abundant protein in the human body, accounting for approximately 25% of the total protein mass. It is the main component of the ECM and serves as a stmctural protein in connective tissues, such as skin, bone, cartilage, and blood vessels. Twenty-eight types of collagen have been identified in humans to date (Kar et al. 2006). Among these, collagen types I-III are the most abundant. 

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