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TissuePart-II - Glandular Epithelium a gland may consist of...

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Glandular Epithelium a gland may consist of one cell or a group of cells highly specialized to secrete substances into ducts, onto surfaces, or into the blood. Glands are classified as exocrine or endocrine Unicellular Exocrine Glands Goblet Cell simplest form of exocrine gland; isolated secretory cell in an epithelium goblet cells are found in the epithelial lining of the intestine and portions of the respiratory tract goblet cells are goblet-shaped, thin at the basal side and expanded on the apical portion apical portion of goblet cell is filled with large mucous producing secretory granules Exocrine Glands Two Types Unicellular- are single celled glands interspersed within various columnar epithelia ex. Goblet cell ductless glands that expel their contents directly onto the surface of the tissue Multicellular- composed of numerous secretory cells in addition to cells that form the walls of the ducts divided into simple or compound simple- ducts do not branch or have only a few branches compound- ducts have multiple branches classified according to the shape of the secretory portion tubular- resembles a ductule acinar- resembles a flask tuboacinar- has both ductule and flask shaped secretory portions To classify multicellular exocrine glands look at 1. the structure of their duct systems : if the gland has a single non ramified duct connecting its secretory part to the surface, it will be called simple if the gland has a ramified duct system it will be called compound . Single unbranched ducts: in green ; Secretory parts of glands: in red ; Lining epithelium: in blue .
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2. the structure of their secretory parts : if the secretory parts form little tubes, the gland will be called tubular . Tubes can be coiled and in this case glands will be called coiled tubular . if the secretory parts form little bags, it will be called alveolar or ascinar Both shapes (tubes and bags) can be present in a compound exocrine glands. In such a case the gland will be called tubulo-alveolar . Most of the time each bag (or tube) is connected to its own private duct. However, some simple exocrine glands have several bags (or tubes) sharing the same duct: they are called branched . Exocrine Glands multicellular exocrine glands can also be classed according to the means by which they discharge the secretory product merocrine- products secreted by exocytosis through the cell membrane (salivary,pancreatic and certain sweat glands) apocrine- a portion of the cell is pinched off and discharged with the secretions (mammary and certain sweat glands) holocrine- the entire cell is discharged along with the secretory product (sebaceous glands of the skin) Endocrine Glands merocrine type glands that secrete their contents into the extracellular fluid where they diffuse into the blood are always hormones- chemical products that regulate various physiological activities pituitary, thyroid, adrenals ....
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