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III. Microanatomy of Extrinsic Exocrine Glands Associated with the Digestive Tract A. Terms used to describe ducts of compound exocrine glands 1. Terms based on morphology of the lining epithelium a. Intercalated ducts - lined by simple squamous to simple cuboidal epithelia, may have myoepithelial cells - smallest ducts, connected to secretory units b. Striated ducts - lined by simple columnar epithelium with basal infoldings in the cells - function in water reabsorption from the secretions of the gland c. Excretory ducts - lined with simple columnar to stratified columnar epithelium 2. Terms based on position of the duct a. Intralobular ducts - located within a lobule in a gland - therefore not located in a connective tissue septum b. Interlobular ducts - located between lobules (smaller connective tissue-wrapped components) of a gland - therefore located within a connective tissue septum which separates lobules of a gland c. Interlobar ducts - located between lobes (larger connective tissue-wrapped components) of a gland - therefore located within a connective tissue septum which separates lobes of a gland Intercalated ducts and striated ducts are always intralobular, but excretory ducts may be interlobular or interlobar. Interlobar ducts would be larger in diameter, have a thicker lining epithelium, and be running in larger connective tissue septa than interlobular ducts. 12
B. Salivary glands (Figure 16.22 - 16.28, Plate 47, 48, 49) 1. Three pairs of major salivary glands occur in humans a. Parotid glands b. Submandibular (submaxillary) glands c. Sublingual glands 2. Minor salivary glands are widespread within the wall of the oral cavity and usually are seromucous (tubuloacinar). 3. Organization of the major salivary glands a. Major salivary glands are compound acinar (serous) or compound tubulo-acinar (seromucous, also called mixed) glands. b. Secretory units are usually surrounded by myoepithelial cells. c. Ducts (1) Intercalated - simple cuboidal epithelium (2) Striated - simple columnar epithelium with basal infoldings which concentrates secretory product by removing sodium ions and water (3) Excretory - simple columnar, pseudostratified columnar, stratified cuboidal, or stratified columnar epithelium d. Capsule - moderately dense FECT e. Loose to moderately dense FECT septae divide the glands into lobes and lobules and are continuous with the loose FECT stroma within the lobules. 4. The major salivary glands in humans differ in type of secretion and in the types of ducts present. Other mammals have different patterns. a. Parotid = totally pure serous acinar units with intercalated, striated, and excretory ducts present b. Submandibular = pure serous acinar units predominate but mucous units capped with serous demilunes (mixed units) occur in many areas of the gland; intercalated, striated, and excretory ducts are present. c. Sublingual = mucous acini and short tubules with serous demilunes (mixed units) are the most frequent unit. A few serous acini may occur but no large areas of serous units occur. Only intercalated and excretory ducts occur. NOTE – the demilune arrangement of the serous cells in seen in routine preparations of the submandibular and sublingual salivary glands appears to be a fixation artifact, since rapid freezing shows intermingled serous and mucous cells (see Figure 16.23). 13
Page 1 and 2: HISTOLOGY OF THE DIGESTIVE SYSTEM I
Page 3 and 4: 2. Teeth (Figure 16.6, 16.7, 16.10
Page 5 and 6: (3) Circumvallate Papillae (a) Flat
Page 7 and 8: [b] Parietal cells (or oxyntic cell
Page 9 and 10: (c) Most of these cells are small,
Page 11: c. The muscularis externa typically
Page 15 and 16: D. Liver (Figure 18.1 - 18.14, Plat

HISTOLOGY OF THE DIGESTIVE SYSTEM I ... - Faculty.rmc.edu

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