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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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