Tissues1 - filtration Cuboidal or columnar cells which...

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Tissues, Glands, and Membranes A tissue is a group of cells with similar structure and function, as well as the extracellular substances located between the cells. Histology is the study of tissues. Epithelial Tissue Epithelial tissue covers surfaces, usually has a basement membrane, has little extracellular material, and has no blood vessels. Functions of Epithelia General functions of epithelia include protection, acting as barriers, and secretion and absorption of substances. Classification of Epithelia Simple epithelium has one layer of cells, whereas stratified epithelium has more than one. Pseudostratified columnar epithelium is simple epithelium that appears to have two or more cell layers. Transitional epithelium is stratified epithelium that can be greatly stretched. Structural and Functional Relationships Simple epithelium is involved with diffusion, secretion, or absorption. Stratified epithelium serves a protective role. Squamous cells function in diffusion or
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Unformatted text preview: filtration. Cuboidal or columnar cells, which contain more organelles, secrete or absorb. • A smooth, free surface reduces friction. Microvilli increase surface area, and cilia move materials over the cell surface. • Desmosomes mechanically bind cells together, tight junctions form a permeability barrier, and gap junctions allow intercellular communication. • Hemidesmosomes mechanically bind cells to the basement membrane. Glands • A gland is a single cell or a multicellular structure that secretes. • Exocrine glands have ducts, and endocrine glands do not. Connective Tissue • Connective tissue holds cells and tissues together. • Connective tissue has an extracellular matrix consisting of protein fibers, ground substance, and fluid. • Collagen fibers are flexible but resist stretching, reticular fibers form a fiber network, and elastic fibers recoil. • Blast cells form the matrix, cyte cells maintain it, and clast cells break it down....
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