Digestive system lecture

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123 Terms

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Oral cavity functions
* mastication
* deglutination
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Pharynx/esophagus functions
* swallowing
* transport
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stomach functions
* mechanical digestion
* intital digestion of proteins and lipids

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small intestine functions
chemical and mechanical digestion

absorption
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large intestine functions
* compaction of feces
* absorption
* defecation
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What is ingestion?
taking food and drinks into oral cavity
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what is digestion?
* breaking down foods into usable forms
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What is the difference between chemical and mechanical digestion?
* chemical: use of enzymes to break down polymers into monomers for absorption
* mechanical: alters consistency of food to ease transport
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What is the movement of materials into digestive tract epithelium → interstitial fluid→ blood/lymph?
absorption
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What is compaction?
absorbing all usable material and consolidating the ingestible and nonabsorbable materials as feces
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What is the function of protection of the digestive system( (epithelium and lymphoid tissue)
* epithelia protect against abrasion, chemical damage, pathogens
* lymphoid tissue protects against pathogens that enter interstitial fluid
* stomach acid
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What structures are included in the digestive tract (alimentary canal)?
mouth, esophagus, stomach, small intestine, large intestine
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What are the accessory organs?
teeth, tongue, salivary glands, liver, gallbladder, pancreas
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What are the functions of the accessory organs?
many produce secretions that are released into the lumen of digestive tract through ducts
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What are the 4 digestive tract layers? list from innermost to outermost.
* mucosa
* submucosa
* muscularis externa
* serosa
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What is the function of mucosa?
* absorb monosaccharides, amino acids, lipids
* protect from abrasion
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What are the functions of submucosa?
* contains blood vessels and lymphatic vessels
* exocrine glands
* MALT
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What are the functions of muscularis externa?
* inner circular/outer longitudinal smooth muscle
* stomach contains a third oblique layer
* churns and propels waste
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What are the functions of serosa?
* secrete serous fluid
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Which membrane maintains spatial relationships between organs?
* mesentery
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What is the function of mesentery?
* supply blood vessels, nerves, lymphatic vessels, lymph nodes
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What are the two posterior mesenteries?
mesocolon and mesentery proper
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What are the two anterior mesenteries?
lesser omentum and greater omentum
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What is peritonitis?
acute inflammation of the peritoneum caused my infection microbes, GI tract rupture, perforated ulcer, trauma, appendicitis
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which cranial nerve controls the tongue?
CN XII (hypoglossal)
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What is the function of the tongue?
* mechanically break up food
* manipulate food into a bolus
* glands secrete saliva and ligual lipase
* ducts of salivary glands open near lingual frenulum
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What are the functions of saliva?
* mucus for lubrication
* enzymes that initiate the digestion of carbs and lipids
* IgA antibodies and lysozyme
* solvent for dissolving food molecules
* bicarbonate that neutralizes bacterial acids
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What is the function of the upper esophageal sphincter?
prevents air from entering esophagus when contracted
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How many layers of muscularis externa is in the stomach? what is the function of the extra layer?
* 3
* prevents over-stretching and helps churn food
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What is the function of the mucus neck cell?
* secrete acidic fluid containing mucin
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What do parietal cells secrete?
* Hydrochloric acid (HCl)
* intrinsic factor (IF)
* Ghrelin
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What is ghrelin?
appetite stimulating hormone
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What is the importance of IF and B12?
* essential for Hb synthesis
* both get taken up via receptor mediated endocytosis
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What do the chief cells secrete?
* pepsinogen
* gastric lipase
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What activates pepsinogen to pepsin?
HCl
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Pepsin
initiates chemical digestion of protein
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what do enteroendocrine cells secrete
* localized paracrines
* gastrin from G cells
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What is the function of gastrin?
* stimulates parietal and chief cell secretion
* increases stomach motility, relaxes pyloric sphincter, constricts cardiac sphincter
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Regenerative cells
* stem cells that replace lost pit and gland cells
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G cells
secrete gastrin
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Parietal cells generate __ from __ , then pump into lumen while exchanging __.
* H+
* carbonic acid
* K+
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what is bicarbonate exchanged for in gastric hydrochoric acid?
* plasma chloride ions
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CO2 is converted to carbonic acid, carbonic acid dissociates into _____ ,__ __*, ,*__ *then* __*, _*__ *moves in and __moves out.*
* K+, H+, HCO3-
* chloride moves in
* bicarbonate moves out
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What pump facilitates the gastric hydrochloric acid formula
protein H+ K+ ATPase pump
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What is the function of gastric hydrochloric acid
* kills microbes, denatures food enzymes, breaks down plant cell walls, meat CTs
* activates pepsinogen and lingual lipase
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Where does the initial digestion of lipids take place, and by what?
in the mouth/stomach by lingual lipase and gastric lipase
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How is pepsin autocatalytic?
catalyzes own reaction by splitting amino acids to activate pepsinogen, that activates more pepsin
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why is there little absorption in the stomach?
* thick mucus
* lack of transport proteins
* tight junctions
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Mucus cells contain ___________ which converts ethanol to acetaldehyde
alcohol dehydrogenase
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Function of duodenum
* recieves chyme from stomach and secretions from accessory organs
* neutralizes stomach acid
* inactivates pepsin
* emulsifies lipids
* site of pancreatic enzyme function
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Jejunum function
* majority of chemical digestion and absorption occur here
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Ileum function
* lymphoid nodules protect against bacteria
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Small intestine villi
* absorb nutrients and deliver to liver
* each contains a lacteal
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What is a lacteal?
* lymphatic capillary that absorbs lipids
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small intestine microvilli
* form brush border enzymes (BBEs)
* increase surface area for absorption
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BBE functions
* carry out final stage of digestion
* peptidases and enteropeptidase
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Small intestine - intestinal crypts

* what does upper portion contain?
* what does lower portion contain?
* what cell secretes lysozyme?
* upper: enterocytes, goblet cells
* lower: stem cells
* paneth cells
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What is the function of the duodenal glands?
* produce mucus to protect epithelium
* contains bicarbonate ions
* increases pH
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__ of foodstuffs are used to make __ for biosynthesis
* monomers
* ATP
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What is a hydrolysis reaction?
use water to break polymers into monomers
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What initiates digestion of carbohydrates?
* salivary amylase
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What initiates digestion of lipids?
* lingual and gastric lipase
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what initiates digestion of proteins?
* pepsin
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Maltase, sucrase, lactase:

* source?
* target?
* products?
* brush border of small intestine
* maltose, sucrose, lactose
* monosaccharides
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pancreatic amylase:

* source
* target
* products
* pancreas
* starch
* oligosacchardies, trisaccharides, maltose
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salivary amylase

* source
* target
* products
* salivary glands
* starch
* oligosaccharides, trisaccharides, maltose
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What bond does pepsin break?
tyrosine and phenylalanine bond
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Pepsinogen (pepsin) --- stomach

* source
* target
* products
* chief cells of gastric glands
* proteins and polypeptides
* smaller polypeptides
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pepsinogen (pepsin) remarks (3)?
* activated by HCl
* autocatalytic
* breaks bonds between tyrosine and phenylalanine
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enteropeptidase --- sm intestine

* source
* target
* products
* brush border and lumen of sm intestine
* trypsinogen
* trypsin
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trypsinogen --- sm intestine

* source
* target
* products
* pancreatic juice
* proteins and polypeptides
* smaller polypeptides
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chymotrypsinogen (chymotrypsin)

procarboxypeptidase (carboxypeptidase) --- sm intestine

* source
* target
* products
* activated by?
* pancreatic juice
* proteins and polypeptides
* smaller polypeptides
* activated by trypsin
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proelastase (elastase) --- sm intestine

* source
* target
* products
* activated by
* pancreatic juice
* elastin
* smaller polypeptides
* trypsin
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dipeptidases and peptidases --- sm intestine

* source
* target
* products
* brush border of small intestine
* dipeptides and tripeptides
* amino acids
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Which two factors break lipid globules into smaller globules?
* stomach churning and segmentation
* called emulsification
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*and* ___ from bile coat surface of small globules
* lecithin
* bile acids
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what is the purpose of coating the small globules?
* prevent them from coming back together
* increase SA for lipase enzymes
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Lipase breaks ____ into ____ and a ____
* triglycerides
* 2 FFAs
* monoglyceride
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lingual lipase

* source
* target
* products
* glands of tongue
* triglycerides
* FFAs and monoglycerides
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gastric lipase

* source
* target
* products
* chief cells of gastric glands
* triglycerides
* FFAs and monoglycerides
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pancreatic lipase

* source
* target
* products
* pancreatic juice
* triglycerides
* FFAs and monoglycerides
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What 2 nucleases are contained in pancreatic juice?
* deoxyribonuclease
* ribonuclease
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what is the function of deoxyribonuclease and ribonuclease?
* break polymers into nucleotides
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Brush border contains nucleosidases and phosphatases that result in which 3 things?
* sugar (deoxyribose or ribose)
* phosphate ions
* nitrogenous base
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Carb absorption sm intestine

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glucose and galactose move into columnar cell using which transporter?
Sodium-glucose transporter
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carb absorption sm intestine

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What does fructose get converted to?
glucose via facilitated diffusion
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carb absorption sm intestine

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which 3 monosaccharides enter ECF via facilitated diffusion?
* glucose
* fructose
* galactose
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Carb absorption sm intestine

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What is solvent drag?
When theres a high concentraion of solute in lumen, it pulls it to an area of low pressure (IF), to make solute concentration in IF higher
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protein absorption sm intestine

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amino acids move with which transport molecule?
Na+
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protein absorption sm intestine

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Dipeptides and tripeptides move into cells using which cotransport molecule?
H+
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Lipid absorption sm intestine

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What 4 things get taken up by micelles?
* FFAs
* monoglycerides
* cholesterol
* fat-soluble vitamins
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What is a micelle?
* sphere of bile components
* travel to surface of epithelial cells and FFAs diffuse across apical cell membrane
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lipid absorption sm intestine

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Inside the cell, FFAs get converted to ______ in the ___.

Then vescicles of ___ travel to the ___.
* triglycerides
* smooth ER
* triglycerides
* golgi apparatus
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lipid absorption sm intestine

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What is a chylomicron?
* triglyceride (and some cholesterol) coated with proteins and phospholipids
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what happens when chylomicrons leave the cell?
they get taken up by lacteals
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Functions of large intestine?
* dehydrates food through absorption of water and ions
* vitamin synthesis and absorption

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What do laneth cells in the large intestine produce?
lysozyme
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What is osmosis (water absorption) facilitated by?
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Pancreas exocrine functions
* acinar cells secrete pancreatic juice into duodenum
* \
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pancreas endocrine functions
islets produce and secrete insulin and glucagon