Canadian Medical Guide > Anatomy > Cells > Cellular Structures > Cell Surface Extensions Terms and Definitions




Cell Surface Extensions

Medical Definition: Specialized structures of the cell that extend the cell membrane and project out from the cell surface.
Guide Notes: GEN: avoid; prefer specifics
Cell Surface Extensions Categories.
Canadian Medical Guide Definition Cellulosomes - Extracellular structures found in a variety of microorganisms. They contain CELLULASES and play an important role in the digestion of CELLULOSE.
Canadian Medical Guide Definition Cilia - Populations of thin, motile processes found covering the surface of ciliates (CILIOPHORA) or the free surface of the cells making up ciliated EPITHELIUM. Each cilium arises from a basic granule in the superficial layer of CYTOPLASM. The movement of cilia propels ciliates through the liquid in which they live. The movement of cilia on a ciliated epithelium serves to propel a surface layer of mucus or fluid. (King & Stansfield, A Dictionary of Genetics, 4th ed)
Canadian Medical Guide Definition Fimbriae, Bacterial - Thin, hairlike appendages, 1 to 20 microns in length and often occurring in large numbers, present on the cells of gram-negative bacteria, particularly Enterobacteriaceae and Neisseria. Unlike flagella, they do not possess motility, but being protein (pilin) in nature, they possess antigenic and hemagglutinating properties. They are of medical importance because some fimbriae mediate the attachment of bacteria to cells via adhesins (ADHESINS, BACTERIAL). Bacterial fimbriae refer to common pili, to be distinguished from the preferred use of "pili", which is confined to sex pili (PILI, SEX).
Canadian Medical Guide Definition Flagella - A whiplike motility appendage present on the surface cells. Prokaryote flagella are composed of a protein called FLAGELLIN. Bacteria can have a single flagellum, a tuft at one pole, or multiple flagella covering the entire surface. In eukaryotes, flagella are threadlike protoplasmic extensions used to propel flagellates and sperm. Flagella have the same basic structure as CILIA but are longer in proportion to the cell bearing them and present in much smaller numbers. (From King & Stansfield, A Dictionary of Genetics, 4th ed)
Canadian Medical Guide Definition Microvilli - Minute projections of cell membranes which greatly increase the surface area of the cell.
Canadian Medical Guide Definition Pili, Sex - Filamentous or elongated proteinaceous structures which extend from the cell surface in gram-negative bacteria that contain certain types of conjugative plasmid. These pili are the organs associated with genetic transfer and have essential roles in conjugation. Normally, only one or a few pili occur on a given donor cell. (From Singleton & Sainsbury, Dictionary of Microbiology and Molecular Biology, 2d ed, p675) This preferred use of "pili" refers to the sexual appendage, to be distinguished from bacterial fimbriae (FIMBRIAE, BACTERIAL), also known as common pili, which are usually concerned with adhesion.
Canadian Medical Guide Definition Pseudopodia - A dynamic actin-rich extension of the surface of an animal cell used for locomotion or prehension of food.

Cell Surface Extensions Medical Definitions and Terms

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