Histology 1.Epithelial tissues 2.Connective tissues 3.Muscle tissues 4.Nervous tissues.
Connective Tissues
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Connective tissues: Loose Connective Tissue Loose connective tissue is more prevalent in the body than dense connective tissue. It is characterized by a loose, irregular arrangement of connective tissue fibers and abundant ground substance. Numerous connective tissue cells and fibers are found in the matrix. Collagen fibers, fibroblasts, adipose cells, mast cells, and macrophages predominate in loose connective tissue, with fibroblasts being the most common cell types. The overview figure shows the various types of cells and fibers that are present in the loose connective tissue. Dense Connective Tissue In contrast, dense connective tissue contains thicker and more densely packed collagen fibers, with fewer cell types and less ground substance. The collagen fibers in dense irregular connective tissue exhibit a random and irregular orientation. Dense connective tissue is present in the dermis of skin, in capsules of different organs, and in areas that need strong support. In contrast, dense regular connective tissue contains densely packed collagen fibers that exhibit a regular and parallel arrangement. This type of tissue is found in the tendons and ligaments. In both connective tissue types, fibroblasts are the most abundant cells, which are located between the dense collagen bundles. Cells of the Connective Tissue The two most common cell types in the connective tissue are the active fibroblasts and the inactive or resting fibroblasts, the fibrocytes. Fusiform-shaped fibroblasts synthesize all of the connective tissue fibers and the extracellular ground substance. Adipose (fat) cells, which may occur singly or in groups, are seen frequently in the connective tissue; these cells store fat.When adipose cells predominate, the connective tissue is called an adipose tissue. Macrophages or histiocytes are phagocytic cells and are most numerous in loose connective tissue. They are difficult to distinguish from fibroblasts, unless they are performing phagocytic activity and contain ingested material in their cytoplasm. Mast cells, usually closely associated with blood vessels, are widely distributed in the connective tissue of the skin and in the digestive and respiratory organs.Mast cells are spherical cells filled with fine, regular dark-staining and basophilic granules.
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Tissues
Transcript of Connective Tissues
Connective tissues:Loose Connective TissueLoose connective tissue is more prevalent in the body than dense connective tissue. It is characterizedby a loose, irregular arrangement of connective tissue fbers and abundant ground substance.Numerous connective tissue cells and fbers are found in the matri. Collagen fbers,fbroblasts, adipose cells, mast cells, and macrophages predominate in loose connective tissue,!ith fbroblasts being the most common cell types. The overvie! fgure sho!s the various typesof cells and fbers that are present in the loose connective tissue."ense Connective TissueIn contrast, dense connective tissue contains thic#er and more densely pac#ed collagen fbers,!ith fe!er cell types and less ground substance. The collagen fbers in dense irregular connectivetissue ehibit a random and irregular orientation. "ense connective tissue is present in the dermisof s#in, in capsules of di$erent organs, and in areas that need strong support. In contrast,dense regular connective tissue contains densely pac#ed collagen fbers that ehibit a regular andparallel arrangement. This type of tissue is found in the tendons and ligaments. In both connectivetissue types, fbroblasts are the most abundant cells, !hich are located bet!een the dense collagenbundles.Cells of the Connective TissueThe t!o most common cell types in the connective tissue are the active fbroblasts and the inactiveor resting fbroblasts, the fbrocytes. %usiform&shaped fbroblasts synthesize all of the connectivetissue fbers and the etracellular ground substance.Adipose (fat) cells, !hich may occur singly or in groups, are seen fre'uently in the connectivetissue( these cells store fat.)hen adipose cells predominate, the connective tissue is called anadipose tissue.Macrophages or histiocytes are phagocytic cells and are most numerous in loose connectivetissue. They are di*cult to distinguish from fbroblasts, unless they are performing phagocyticactivity and contain ingested material in their cytoplasm.Mast cells, usually closely associated !ith blood vessels, are !idely distributed in the connectivetissue of the s#in and in the digestive and respiratory organs.+ast cells are spherical cellsflled !ith fne, regular dar#&staining and basophilic granules.lasma cells arise from the lymphocytes that migrate into the connective tissue. These cellsare found in great abundance in loose connective tissue and lymphatic tissue of the respiratoryand digestive tracts.Leu!ocytes, or !hite blood cells, neutrophils, and eosinophils, migrate into the connectivetissue from the blood vessels. Their main function is to defend the organism against bacterialinvasion or foreign matter.%ibroblasts and adipose cells are permanent or resident connective tissue cells. Neutrophils,eosinophils, plasma cells, mast cells, and macrophages migrate from the blood vessels and ta#eresidence in the connective tissue of di$erent regions of the body.
