Histology of Digestive System

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4 layers of GI tract

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4 layers of GI tract

mucosa, submucosa, muscularis, serosa

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___________ layer of GI tract : epithelium, lamina propria and muscularis mucosa

mucosa

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___________ layer of GI tract : dense connective tissue, vessels + n, glands, Meissner's plexus

submucosa

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epithelium of esophagus mucosa

nonkeratinized stratified squamous epithelium

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epithelium of stomach mucosa

monomorphous simple columnar epithelium

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epithelium of intestine mucosa

polymorphous simple columnar epithelium

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______________ of mucosa has loose connective tissue, n, leukocytes and glands

lamina propria

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muscularis mucosae of gi tract consists of

smooth m fibers

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stratified squamous epithelium is ________ mucosa, monomorphous columnar epithelium is _____________ mucosa and polymorphous columnar epithelium is ________ mucosa

protective secreting absorptive

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where is secreting mucosa (monomorphous columnar)

stomach

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where is protective mucosa (SSE)

oral, pharynx, esophagus, anal canal

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where is absorptive mucosa (polymorphous columnar)

LI

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Where is MALT

lamina propria of GI tract mucosa

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Glands in lamina propria of mucosa in stomach vs intestines

gastric Lieberk├╝hn

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2 layers of muscularis mucosae of mucosa of GI tract

inner circular outer longitudinal

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submucosa of which parts of the GI tract have glands

esophagus and duodenum

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Muscularis propria of GI tract : in bw 2 layers there is

Myenteric Auerbach plexus

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muscularis propria of stomach

inner circular, outer longitudinal and extra oblique layer

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m fibers of muscularis propria of GI tract

striated m fibers in upper 1/3 smooth m fibers in 2/3

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serosa vs adventitia cover

seroa - intraperitoneal adventitia - extraperitoneal

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layers of GI tract serosa

subserous inner layer mesothelium (SSE)

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why does esophagus look stellate

longitudinal folds in lumen (for distention)

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mucosa of esophagus

nonkeratinized stratified squamous epithelium

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submucosa esophageal glands secrete

acid mucins

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covering of adventitia/serosa

adventitia until pierces diaphragm, then serosa

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gastro-esophageal junction (z line)

non-keratinized stratified squamous to simple columnar

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role of gastro-esophageal jxn

functional sphincter to prevent reflux

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what is the gastro-esophageal jxn a location of?

patho changes (barrett's, epidermoid carcinoma)

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electrolytes, pepsinogen, hydrochloric acid, B12, and mucins are in

gastric secretions

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which part of stomach makes chyme

body

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_______ is a narrow region at the gastroesophageal jxn

cardia

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stomach is divided histologically in 3 regions based on glands

cardiac glands, fundic glands and pyloric glands

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rugae of stomach are made of

mucosa and submucosa

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mamillated areas of stomach ->

gastric pits

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lining epithelium of stomach mucosa

simple columnar epithelium composed entirely of mucous cells (mucinogen granules)

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structure of surface mucous cells of stomach

nucleus and golgi below mucous cup, tightly attached by occluding jxns, w. microvilli and covered by glycocalyx

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______ is high alkaline (entrapped bicarbonate ions) + insoluble + has PGE2

mucus of stomach

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what is special about gastric lamina propria

no lymph tissue

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which stomach glands are very long and have 5 diff cell types

fundic glands

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_________ cells of fundic glands are in bw neck of gland w/ gastric pit

stem

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mucous neck cells of fundic gland

short + spherical, secrete less mucinogen (induced by vagal stimulation)

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chief zymogenic cells of fundic gland secrete

pepsinogen and gastric lipase

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parietal oxyntic cells of fundic gland role

release hydrochloric acid and gastric IF

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parietal oxyntic cells of fundic gland structure

pyramidal cells w/ intracell canaliculi w/ tubulovesicular system bordering

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number of microvilli and the abundance of vesicles of the tubulovesicular system of parietal oxyntic cells vary with

Hcl secretory activity of parietal cells (active secretion = more microvilli, less system)

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how does tubulovesicular system contribute to acid secretion

stores plasma membrane to increase surface + proton pumps for acid production

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parietal cells of fundic glands contain important quantities of

carbonic anhydrase

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parietal cells of fundic glands are 3 receptors:

gastrin (HCl secretion) histamine (Ach + gastrin effects Ach (gastrin secretion)

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__________ are cells that are found everywhere in fundic gland and secrete paracrine + endocrine effects

DNES

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open vs closed enteroendocrine cells of fundic gland

closed - usually on basal lamina

open - extensions exposed to gland lumen

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how are enteroendocrine cells identified

immunohistochemical stains

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gastrin, serotonin, histamine, PP (pancreatic polypeptide) and VIP (vasoactive intestinal peptide) are secreted by

enteroendocrine cells of fundic gland

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How are pyloric glands different from the gastric glands and cardiac glands?

deeper pits and highly convoluted

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unlike fundic glands, pyloric gland epithelia consist only of

mucous cells

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compared to the fundic gland, pyloric gland have no _______ cells but have far more _______-

chief cells G cells (enteroendocrine)

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in SI, digestion is facilitated by

enzymes + alkaline buffer

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what has plicae circulares/valves of Kerckring, villi and microvilli?

SI

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what decreases the velocity of chyme movement

valves of kerckring

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_______ consist of core of loose connective tissue covered by simple columnar epithelium, w/ cap loops and lacteal

villi (of SI)

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role of smooth m cells of villi

contract to force lymph from lacteal to lymph vessel

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where are microvilli found

absorptive cells of the small intestine

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function of occluding jxns of enterocytes

barrier bw intestinal lumen and epithelial intercell compartment, forces digestive products to cross brush border

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lateral domain of enterocytes contain

occluding jxns and lateral infoldings

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secretory fxn of enterocytes

synthesis of glycoprotein enzymes by Golgi

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abundant organelles of enterocytes

Golgi (secretion), sER (absorption of fats), elongated mitochondria

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digestion, absorption, re esterification and chylomicron formation are roles of

enterocytes (absorptive cells)

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what enzymes digest carbs in enterocyte

amylase

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digestion of proteins by enterocyte

pepsin in stomach -> peptidases of enterocytes

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digestion of lipids of enterocytes

triglycerides broken down + emulsified by bile salts -> enterocyte re-esterified to triglycerides -> lacteals -> liver

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goblet cell # increases from which locations of GI tract

duodenum to ileum

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fxn of goblet cells of SI epithelium

secrete mucus by mucinogen

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DES cells of SI epithelium

produce paracrine and endocrine hormones, regulating secretion + motility

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where are DES cells located

SI, base of Lieberkuhn crypt, sometimes to surface of intestinal villi

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CKK, GIP, VIP and secretin are found in which cells of SI epithelium

DES cells

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function of M(microfold) cells of SI epithelium

transport antigens in intestines to immune cells in their recesses

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paneth cells

in crypts of epithelium, regulates flora

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lamina propria + submucosa of ileum have

Payer's patches

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Brunner's glands of submucosa of duodenum

protects SI by neutralizing acid in chyme

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what are the cells in intestinal m. externa that are pacemarker cells for motility

interstitial cells of Cajal

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2 kinds of m contraction occur in SI

segmentation (circ layer) and peristalsis (long layer)

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differences of duodenum

contain duodenal papilla of Vater and Brunner's glands in subumucosa

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differences of jejunum

villi narrower, more goblet cells

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___________ has no villi but many crypts of Liuberkuhn

colon

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collagen table, pericryptal fibroblast sheath, GALT are in what of the colon

lamina propria

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