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Accessory Organs Associated with Duodenum. Pancreas – enzymes that complete food digestion, ducted to duodenum via pancreatic ducts Main duct -> Hepatopancreatic ampulla Accessory pancreatic duct -> minor duodenal papilla, pancreatic juice when no bile

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accessory organs associated with duodenum
Accessory Organs Associated with Duodenum
  • Pancreas – enzymes that complete food digestion, ducted to duodenum via pancreatic ducts
  • Main duct -> Hepatopancreatic ampulla
  • Accessory pancreatic duct -> minor duodenal papilla, pancreatic juice when no bile
  • Duct – bicarbonate mucus, acini secrete enzymes

Figure 14.6

enzymes of pancreas
Enzymes of Pancreas
  • Trypsinogen, chymotrypsinogen, procarboxypeptidase
  • Trypsinogen converted to Trypsin by enterokinase in lumen of duodenum
  • Trypsin cleaves other two to make chymotrypsin and carboxypeptidase, and digests dietary protein
  • Pancreatic amylase, pancreatic lipase, ribonuclease, deoxyribonuclease – active after exposure to bile and ions in lumen
regulation of pancreatic secretions
Regulation of Pancreatic Secretions
  • Bile and pancreatic juice secreted in response to vagus stimulation (parasympathetic), inhibited by sympathetic
  • Both stimulated by Cholecystokinin (CCK), gastrin, and secretin
  • CCK released by duodenum in response to fat and acid from stomach.
    • Contraction of gallbladder – bile into duct
    • Secretion of pancreatic enzymes
    • Relaxation of hepatopancreatic sphincter
  • Secretin – stimulates bile and pancreatic duct secretion of bicarbonate, neutralize acid
liver
Liver
  • 4 lobes – rt, lt, quadrate, caudate, sep by falciform ligament = mesentary
  • Round ligament = remnant of umbilical vein, blod from umbilical cord to liver of fetus
  • Portal hepatitis – entry of hepatic portal vein, proper hepatic artery, exit of bile passages
  • Gallbladder associated
microscopic liver
Microscopic liver
  • Hepatic lobules – central veins, cuboidal hepatocytes
  • Hepatic Triad – artery + vein (branches of proper hepatic artery and hepatic portal vein), bile ductule
  • Hepatic sinusoid – fenestrated endothelium sep hepatocyte from bloodstream, blood plasma fills, blood directly from intestine
    • Liver gets first dibs on glucose, AA, iron, vitamis, nutrients
    • Removes hormones, toxins, bile pigments, drugs
    • Secretes some blood proteins
bile secretion
Bile Secretion
  • Bile canaliculi, bile ductules of triads, left and right hepatic ducts ->common hepatic duct
  • Hepatic and cystic duct join = bile duct
  • Bile duct joins pancreatic duct = hepatopancreatic ampulla
  • Enter duodenum=major duodenal papilla, heptopancreatic sphincter (sp of Oddi)
slide7
Bile
  • Yellow-green color
  • Watery solution contain bile salts and pigments, cholesterol, phospholipids, electrolytes
    • Bilirubin – breakdown product of Hb
  • Only bile salts and phospholipids aid digestion – emulsify fats, more SA for fat digesting enzymes to work on
accessory digestive organs gall bladder
Accessory Digestive OrgansGall Bladder
  • Thin walled green sac
  • When not eating bile stored here
  • Concentrated by water removal
  • Fatty meal enters duodenum, bile released due to hormonal stimulus
gallstones
Gallstones
  • Bile stored for too long or too much water removed, cholesterol crystallizes
  • Blockage of common hepatic or bile ducts prevent bile into small intestine, backs up into liver
  • Bile pigments enter blood and circulate, yellowing jaundice

http://gogogojiteam.com/gallstone.html

organs of alimentary canal small intestine
Organs of Alimentary CanalSmall Intestine
  • MAJOR digestive organ
  • 3 subdivision
    • Duodenum
    • Jejunum
    • Ileum – meets large intestine at ileocecal valve
  • Only able to process small amount of food at time, pyloric sphincter controls food movement
walls of small intestine
Walls of Small Intestine
  • Nearly all food absorption
  • 3 structures in wall increase absorptive surface
    • Microvilli – plasma membrane – brush border enzymes – digestion of protein and carbs
    • Villi – mucosa, w/in each are capillaries and lacteal duct (fat), food absorbed, absorptive and goblet cells
    • Circular folds – deep fold of mucosa and submucosa, don’t disappear as fill with food
  • All decrease as move along
  • Peyer’s Patches increase – collections of lymphatic tissue
    • Bacteria in food!

Figure 14.7

cells of villi
Cells of Villi
  • Absorptive cells line villi, have microvilli
    • Contain brush border enzymes – enterokinase – remember pancreatic Trypsinogen
structures of sm intestine
Structures of Sm. Intestine
  • Crypts of Lieberkuhn – glands at base of villi, extend to muscularis mucosa – absorptive, goblet cells, stem cells, Paneth cells (lysozyme, phospholipase, defensins)
  • Brunner glands – submucosa – bicarbonate mucus (unique to duodenum)
  • Peyer patches – lymphatic nodules - ileum
motility of sm intestine
Motility of Sm. Intestine
  • Segmentation vs. Peristalsis
  • Mix nutrients
  • Churn chyme, contact with mucosa for contact digestion and absorption
  • Move to large intestine
organs of alimentary canal large intestine
Organs of Alimentary CanalLarge Intestine
  • Ileocecal valve to anus, appendix
  • Absorb water and eliminate indigestible food as feces
  • No villi
  • Goblet cells in mucosa produce HCO-3 rich mucus, lubricant
  • Divisions
    • Cecum, Appendix, Colon, Rectum, Anal Canal
    • Colon – ascending, transverse, descending, sigmoid
    • Anus – internal and external sphincters, anal columns and sinuses

Figure 14.8

bacteria and gas
Bacteria and Gas
  • Bacterial flora – ferment cellulose and other undigested nutrients
  • Synthesize B vitamins, vitamin K which are absorbed by colon
    • Don’t get enough vitamin K in diet
  • Expel about 500ml of gas
    • Some from swallowed air, some from bacterial digestion
absorption
Absorption
  • 12-24 from meal to feces
  • Reabsorbs water and electrolytes
  • Feces – 75% water and 25% solids
    • Solids – 30% bacteria, 30% undigested fiber, 10-20% fat (not diet), epithelial cells, salts, mucus, etc
defecation
Defecation
  • Stretching of rectum stimulates defecation
  • Intrinsic defecation reflex – stretch signals travel myenteric nerve plexus to muscularis of descending, sigmoid colon, rectum
    • Stimulates peristaltic waves
    • Internal sphincter relaxes – defecation if external also relaxed
  • Need cooperation of parasympathetic defecation reflex – spinal cord
    • Stretch of rectum, signal to sacral of spinal cord
    • Return via parasympathetic fibers, intensifies peristalsis
    • Parasympathetic fibers relax internal sphincter
functions of the digestive system ingestion
Functions of the Digestive SystemIngestion
  • Food must enter the system to be acted upon
  • Active and voluntary

Figure 14.11

functions of the digestive system propulsion
Functions of the Digestive SystemPropulsion
  • Foods must be processed my multiple organs – move from one to next
  • Swallowing is example
  • Movement depends mostly on peristalsis vs. segmentation
  • Segmentation – small intestine, alternating segments contract, mechanical digestion
functions of the digestive system food breakdown mechanical digestion
Functions of the Digestive SystemFood Breakdown: mechanical digestion
  • Mixing of food in mouth by tongue
  • Churning of food in stomach
  • Segmentation in small intestine
  • Prepare food for enzymatic digestion by breaking into smaller pieces
functions of the digestive system food breakdown chemical digestion
Functions of the Digestive SystemFood Breakdown: chemical digestion
  • Food molecules broken down into building blocks by enzymes
  • Reactions called hydrolysis rxn, water added as bond breaks
  • Carbs (saccharides) we digest – sucrose, lactose, maltose, and starch. Eat cellulose but can’t digest, fiber
  • Proteins (a.a.) – polypeptides or peptides
  • Lipids (fats) – fatty acids and glycerol
functions of the digestive system absorption
Functions of the Digestive SystemAbsorption
  • Transport of digested food into blood from lumen of GI tract
  • Must enter mucosal cells by active or passive transport.
  • Small intestine major site of absorption
functions of the digestive system defecation
Functions of the Digestive SystemDefecation
  • Elimination of indigestible food from GI tract via anus in form of feces
digestion review
Digestion Review

Figure 14.13 (1 of 3