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Histology of the Digestive
System
Ma. Minda Luz M. Manuguid, M.D.
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*Oral Cavity
Lips stratified squamous epithelium;skeletal muscle (orbicularis oris); mucousglands
Gingiva; hard Palate keratinizedepitheliumsoft Palate; buccal Mucosa nonkeratinized
epith. chewing Muscles masseter; pterygoidsTongue skeletal muscles; papillae w/ tastebudsTeeth 20 milk, 32 adult : dentin, enamel,
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Oral CavityTongue 3 layers of skeletal muscles hyoglossus, genioglossus, & 4 typesof papillae:
Foliate leaf-like rareFiliform flame-like most numerous;no taste budsFungiform mushroom-like abundant;few taste budsCircumvallate 9 large roundedpapillae, each surrounded by a collar& a deep furrow; arranged in a V-shaped row at the junction between the
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Tongue; Taste buds
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Teeth
Teeth 20 milkteeth; 32 adult;
incisors for cutting,molars for grindingAmeloblasts secrete enamel
consists of organicProtein & inorganicCa-based salts;harder than boneOdontoblasts secrete dentin
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Salivary glandsSalivary Glands compound tubuloalveolar /tubuloacinar; myoepithelial cells- stellatewith contractile filaments; duct sys:intercalated (cuboidal) striated/secretory
(columnar) interlobular (columnar) primary duct oral cavityParotid largest; mostly serous aciniSubmaxillary / Submandibular mixed serous &mucousSublingual mostly mucousMinor glands von Ebner, labial, lingual
Saliva contains water, ions, enzymes( ptyalin or salivary amylase ), glycoproteins,proteoglycans, sialomucins, IgA
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Salivary glands
Massons trichrome & alcian yellow
Serous demilune
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Salivary glands
striated duct
intercalated
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General Histologic Plan of the GIT
Mucosa simple columnarepithelium with goblet cells+ lamina propria +muscularis mucosaeSubmucosa fibrousconnective tissue; containsblood vessels, nerves,abundant lymphatics,autonomic nerve plexus-Meissners plexusMuscularis Externa innercircular, outer longitudinallayers of smooth muscles; in-between: myenteric nerve
plexus- Auerbachs plexus
S/A
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Nerve plexuses
Auerbachs myenteric plexus Meissners submucosal plexus
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*Oropharynx
Nonkeratinized stratified squamousepithelium
Thick dense elastic layer instead of amuscularis mucosaeMucous glandsMuscles: inner longitudinal , outer
oblique/circular smooth muscles;skeletal muscles : stylopharyngeus,salpingopharyngeus,palatopharyngeus, superior, middle,& inferior constrictor pharyngii
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*Esophagus
Nonkeratinizedstratifiedsquamousepithelium
Mucous glands
Muscles : upper -skeletal; middle 1/3 mixed skeletal &smooth muscles;
lower 1/3 to -
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*StomachRugae temporary mucosal folds evidentwhen stomach is emptyMucosa simple columnar epithelium withseveral other cell types
Chief cells cuboidal to low columnar - secretepepsinogenParietal / Oxyntic spherical to pyramidal -secrete HCl & IFoCNeck cells / mucous secrete mucinArgentaffin / E cells small rounded, granular secrete serotoninA cells secrete glucagonG cells secrete gastrin
D cells secrete somatostatin
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Stomach
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Stomach
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Gastroesophageal &Gastroduodenal
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*Small IntestinesMucosaPlicae circulares / valvulae conniventes / valves
of KerckringVilli; Crypts of Lieberkhn
Lacteals lymphatic channels for absorbed fatAbsorptive columnar cells 3000 microvilli /cell(brush border)Goblet cells mucin; argentaffin serotonin; S
secretin; L glucagon; K GIP; I CCK; D somatostatin; EC serotonin, motilin,substance PPaneth cells pyramidal secrete lysozyme
Submucosa
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SmallIntestines
Duodenum initialpart, receiveschyme from thepylorus of thestomachBrunners glands secrete mucin &Bicarbonate
Jejunum mostnumerous plicae &villi
Ileum lastse ment
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SmallIntestines
plicaevillusmicrovilli
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Small Intestines
Brunners
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*Large IntestinesMucosa many more goblet cells ; largerlumen than small intestines; no PanethcellsRugae temporary mucosal folds
Muscles outer longitudinal layer isdiscontinuous, split into three bands, thetaenia coliHaustra bag-like bulging of the wall inbetween the taenia (excess mucosa)Appendices epiploicae small fatty serosalprotruberancesRectal columns of Morgagni longitudinalmucosal foldsAnus stratified squamous epithelium ;
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Large Intestines
CecumappendixAscending colon
Transverse colonDescending colonSigmoidRectumAnus
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The Appendix
vermiformevagination of thececum
Mucosa simplecolumnar withgoblet cells; fewer,shorter, glands; notaeniaSubmucosa abundant lymphoidfollicles
Muscles innercircular outer
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Accessory Organs of Digestion: Liver
Liver secretes bile,necessary for lipiddigestionLiver lobule histologic unit of Livermorphology polygonal; cords of hepatocytes radiating
outward from thecentral vein (atributary of thehepatic vein);
portal triad / portahe atis: ortal vein
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Liver
Central veinHepatocytesBile canaliculus
Space of DisseSinusoidsHering canals / bileductulesKupffer cellsIto cells
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Liver
C V
Kupffer cells
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Accessory Organs:Gallbladder
Gallbladder storage &concentration of bileMucosa simplecolumnar with microvilli
RugaeLamina propria looseareolar connectivetissue
Rokitansky-Aschoff sinusesMuscles inner oblique,middle transverse , outerlongitudinalSerosa perimuscular
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Accessory Organs:Pancreas
Mixed Exocrine &endocrine glandEndocrine islets of Langerhans ( , , )
secrete glucagon,insulin, somatostatin Exocrine compoundacinar gland similar tothe parotid, but w/ostriated ducts, & theinitial portions of theintercalated ductspenetrate the lumenof the acini, formingthe centroacinar
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PancreasExocrine secretions(alkaline): water, ionsincluding bicarbonate,proenzymes trypsinogen,chymotrypsinogen,carboxypeptidase,ribonuclease,deoxyribonuclease,triacylglycerol lipase,
phospholipase, elastase,amylase. Theseproenzymes are activatedwithin the duodenal
lumen
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