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Glandular Epithelium Glandular Epithelium • Glandular Epithelium: epithelium of cells specialized to produce secretion. All glands are of composed of epithelium. • Secretion – Exocytotic release of products, not metabolic wastes • Molecules to be secreted may be stored in membrane bound secretory granules (vesicles) Gland Categories A) Presence or absence of ducts • Exocrine – ducted • Endocrine - ductless B) Uni- or multicellular C) Mode of secretion D) Secretion products Gland Categories 1) Exocrine - glands that exude secretions into a ductule system. Have two parts, acinous = secretory bulb and ductule. 2) Endocrine - glands exuding secretions directly into body fluids, ultimately blood. 3) Mixed - glands combining both the above characteristics (e.g. liver) in the same cell 4) Paracrine - tissue secretions affecting own cells Cellular Composition 1) Unicellular - single cell gland, Goblet cell; mucous secreting. GI tract, respiratory ducts. Secretion process alters cell and nucleus shape. 2) Multicellular - a) intra epithelial gland - gland is entirely within a layer of epithelium. Common in pseudostratified columnar epith. b) extra epithelial gland - in CT below epithelium; may have different shapes; tubular and saccular (acinar). Mucous Secretory Gland Esophagus Modes of Secretion (how products leave the cell) 1) merocrine - secretion does not affect the well-being of the cell = sweat glands. 2) apocrine - small part of the cell cytoplasm is lost with the secretion; the cell is damaged but not killed = mammary glands. 3) holocrine - great deal of cytoplasm is lost with the secretion; the cell dies. Sebaceous glands. Apocrine Secretion Mammary Gland Epithelial Polarity Absorption Secretion Secretion Products 1) serous - thin, watery fluid, product of serous cells, small pink staining cuboidal cells with spherical to elliptical nuclei; salivary glands, sweat glands, pancreatic acinar. 2) mucous - thicker, viscous secretion, product of mucous cells, large blue staining cuboidal cells with flat, elongate nuclei; GI tract, oral cavity. 3) mixed serous-mucous - oral cavity, salivary. 4) sebaceous - thick, lipid rich secretions of cuboidal cells in certain skin regions - face, nose, axillary and pubic regions. Serous (pancreatic acinar) cell Myoepithelium • Myoepithelium - specialized squamous epithelial cells with powers of contraction; • Surround glandular acini and ducts of many glands, • Contain actin, myosin, cytotokeratin = definitely epithelial in origin, not muscle. Myoepithelial Cell In Salivary Gland Diffuse Neuroendocrine System (DNES) • Paracrine secretion of norepinephrine or serotonin in non-endocrine tissue • Derived from Neural Crest Cells • About 35 types of cells in a variety of tissues such as respiratory, urinary, gastrointestinal, pituitary, thyroid • System formerly known as APUD cells – Amine Precursor Uptake Decarboxylation DNES Cell With Secretory Granules Secretory Membranes • Similar names of secretion products; names based upon type of secretions; form organs (peritonea, gut tube lining, etc.) 1) Serous Membrane - thin, flat layer of squamous epithelial cells which is moistened by exudates from underlying blood vessels. 2) Mucous Membrane - moist epithelial surface, usually columnar, but may be cuboidal or squamous, that is moistened by secretions produced by glands formed by the epithelium itself.
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