and other matter along the surfaces from which theyextend. They also act as a barrier, preventing foreignmatter from entering these cavities.Squamous Epithelial TissueSquamous epithelial tissue is composed of thinplatelike or scalelike cells forming a mosaic pattern(fig. 1-4). This tissue is found in the tympanicmembrane (eardrum) as a single layer of cells, or in thefree skin surface in multiple layers. Squamous tissue isthe main protective tissue of the body.Cuboidal Epithelial TissueThe cells of cuboidal tissue are cubical in shape(fig. 1-5) and are found in the more highly specializedorgans of the body, such as the ovary and the kidney. Inthe kidneys, cuboidal tissue functions in the secretionand absorption of fluids.CONNECTIVE TISSUEThis is the supporting tissue of the variousstructures of the body. It has many variations and is themost widespread tissue of the body. Connective tissueis highly vascular, surrounds other cells, encasesinternal organs, sheathes muscles, wraps bones,encloses joints, and provides the supportingframework of the body. Structures of connective tissuediffer widely, ranging from delicate tissue-papermembranes to rigid bones. Connective tissue iscomposed of cells and extracellular materials(materials found outside the cells). Extracellularmaterials include fibers and the ground substance.The ground substance contains proteins, water, salts,and other diffusible substances. These extracellularmaterials give connective tissue varying amounts ofelasticity and strength, depending on the type of tissueand location. In the following paragraphs we willdiscuss the three predominant types of connectivetissue: areolar, adipose, and osseous.Areolar Connective TissueAreolar tissue consists of a meshwork of thinfibers that interlace in all directions, giving the tissueboth elasticity and tensile strength (fig. 1-6). This typeof connective tissue is extensively distributedthroughout the body, and its chief function is to bindparts of the body together. Areolar tissue allows aconsiderable amount of movement to take placebecause of its elasticity. It is found between musclesand as an outside covering for blood vessels andnerves. The areolar tissue layer connects the bloodvessels and nerves to the surrounding structures.1-4HM3F0105Figure 1-5.—Cuboidal epithelial tissue.HM3F0104Figure 1-4.—Squamous epithelial tissue.HM3F0106Figure 1-6.—Areolar connective tissue.
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