Reticular connective tissue is a type of connective tissue with a network of reticular fibers, made of type III collagen (reticulum = net or network). Reticular fibers are not unique to reticular connective tissue, but only in this type are they dominant. Reticular fibers are synthesized by special fibroblasts called reticular cells. The fibers are thin branching structures.
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Running across it are a number of finer trabeculae of reticular fibers, mostly covered by ramifying cells.
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The fibers form a soft skeleton (stroma) to support the lymphoid organs (lymph node stromal cells, red bone marrow, and spleen). Adipose tissue is held together by reticular fibers.
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A liver biopsy stained with a reticulin stain demonstrating a normal hepatic plate thickness and mild steatosis. Reticular fibers, reticular fibres or reticulin is a type of fiber in connective tissue composed of type III collagen secreted by reticular cells. Reticular fibers crosslink to form a fine meshwork (reticulin). This network acts as a supporting mesh in soft tissues such as liver, bone marrow, and the tissues and organs of the lymphatic system.
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On the other hand, only microfibrils were recognized in the reticular fibers of the capillary sheath. The binding of LFA lectin to the splenic cord was stronger than the capillary sheath. These findings suggested that the reticular fibers of the splenic cord include multiple functional elements and might perform an important role during contraction or dilation of the spleen. On the other hand, the reticular fiber of the capillary sheath resembled the basement membrane of the capillary in its components.
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The 1953 Science article mentioned above concluded that the reticular and regular collagenous materials contains the same four sugars – galactose, glucose, mannose, and fucose – but in a much greater concentration in the reticular than in the collagenous material. In a 1993 paper, the reticular fibers of the capillary sheath and splenic cord were studied and compared in the pig spleen by transmission electron microscopy. This paper attempted to reveal their components and the presence of sialic acid in the amorphous ground substance. Collagen fibrils, elastic fibers, microfibrils, nerve fibers, and smooth muscle cells were observed in the reticular fibers of the splenic cord.
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There are more than 20 types of reticular fibers. In Reticular Connective Tissue type III collagen/reticular fiber (100-150 nm in diameter) is the major fiber component. It forms the architectural framework of liver, adipose tissue, bone marrow, spleen and basement membrane, to name a few.
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Other colors, e.g. yellow and brown, can be present in the sample; they are caused by intrinsic pigments such as melanin. Basal laminae need to be stained by PAS stain or some silver stains, if they have to be well visible. Reticular fibers also require silver stain.
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Mesenchyme is characterized morphologically by a prominent ground substance matrix containing a loose aggregate of reticular fibers and unspecialized mesenchymal stem cells.Mesenchymal tissue Mesenchymal cells can migrate easily, in contrast to epithelial cells, which lack mobility, are organized into closely adherent sheets, and are polarized in an apical-basal orientation.
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The fibroblasts contain organelles that are necessary for the synthesis and excretion of proteins needed to repair the tissue damage. Fibrocytes usually do not leave the connective tissue. Reticular cells are usually larger than fibrocytes. Reticular cells are the fibrocytes of reticular connective tissue and form a network of reticular fibers.
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Collagen is a structural protein, often referred to as “the steel of biological materials”. There are multiple types of collagen: Type I (comprising skin, tendons and ligaments, vasculature and organs, as well as teeth and bone); Type II (a component in cartilage); Type III (often found in reticular fibers); and others. Collagen has a hierarchical structure, forming triple helices, fibrils, and fibers.
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The stroma of the ovary is a unique type of connective tissue abundantly supplied with blood vessels, consisting for the most part of spindle-shaped stroma cells. These appear similar to fibroblasts. The stroma also contains ordinary connective tissue such as reticular fibers and collagen. Ovarian stroma differs from typical connective tissue in that it contains a high number of cells.
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Fibroblastic reticular cells (FRCs) are located in the T cell zone of the cortex. FRCs produce collagen alpha-1(III) rich reticular fibers that form a dense network within the lymphoid tissue. These are connected by collagen XIV, small leucine-rich proteoglycans and lysyl oxidase. The network of fibers supports and guides the movement of dendritic cells (DCs), T lymphocytes and B lymphocytes.
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The reticular dermis is the lower layer of the dermis, found under the papillary dermis, composed of dense irregular connective tissue featuring densely packed collagen fibers. It is the primary location of dermal elastic fibers. The reticular region is usually much thicker than the overlying papillary dermis. It receives its name from the dense concentration of collagenous, elastic, and reticular fibers that weave throughout it.
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A reticular cell is a type of fibroblast that synthesizes collagen alpha-1(III) and uses it to produce reticular fibers. The cell surrounds the fibers with its cytoplasm, isolating it from other tissue components and cells. Reticular cells provide structural support, since they produce and maintain the thin networks of fibres that are a framework for most lymphoid organs. They are found in many tissues including the spleen, lymph nodes and lymph nodules.
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Many adjacent epithelial tissues (which are avascular) get their nutrients from the interstitial fluid of areolar tissue; the lamina propria is areolar in many body locations. Its fibers run in random directions and are mostly collagenous, but elastic and reticular fibers are also present. Areolar tissue is highly variable in appearance. In many serous membranes, it appears as a loose arrangement of collagenous and elastic fibers, scattered cells of various types; abundant ground substance; numerous blood vessels.
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The rough endoplasmic reticulum and Golgi apparatus, as shown by electron micrographs, are not well developed, indicating that the cells are in a resting phase. The collagenous and reticular fibers in the newborn VF are fewer than in the adult one, adding to the immaturity of the vocal fold tissue. In the infant, many fibrous components were seen to extend from the macula flava towards the Reinke's space. Fibronectin is very abundant in the Reinke's space of newborn and infant.
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Lymphoid tissue associated with the lymphatic system is concerned with immune functions in defending the body against infections and the spread of tumours. It consists of connective tissue formed of reticular fibers, with various types of leukocytes (white blood cells), mostly lymphocytes enmeshed in it, through which the lymph passes. Regions of the lymphoid tissue that are densely packed with lymphocytes are known as lymphoid follicles. Lymphoid tissue can either be structurally well organized as lymph nodes or may consist of loosely organized lymphoid follicles known as the mucosa-associated lymphoid tissue (MALT).
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Individuals with GATA2 deficiency commonly exhibit abnormalities in their circulating blood cells (see above "Hematologic" section of Signs and symptoms) that may precede other signs and symptoms of the disease by years. Their bone marrow typically shows significant reductions in one or more types of blood cell lines (i.e. hypocellularity) with characteristic dysplastic features of increased sizes of cells in the red blood cell line (i.e. macrocytic erythropoiesis), small or enlarged megakaryocytes, abnormalities in the maturation of cells in the granulocyte cell line, fibrosis consisting of reticular fibers, increased numbers of T cells containing numerous large granules in their cytoplasm, and in advanced cases increases in blast cell numbers.
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Lymph node tissue showing trabeculae Thin reticular fibers (reticulin) of reticular connective tissue form a supporting meshwork inside the node. The lymph node capsule is composed of dense irregular connective tissue with some plain collagenous fibers, and a number of membranous processes or trabeculae extend from its internal surface. The trabeculae pass inward, radiating toward the center of the node, for about one-third or one-fourth of the space between the circumference and the center of the node. In some animals they are sufficiently well-marked to divide the peripheral or cortical portion of the node into a number of compartments (nodules), but in humans this arrangement is not obvious.
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