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Finishing Digestion: INTESTINE

Finishing Digestion: INTESTINE. Duodenum: completion of digestion. In the duodenum final digestion of all foods takes place. Acidic chyme coming in from the stomach is now neutralized and further digested with new enzymes.

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Finishing Digestion: INTESTINE

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  1. Finishing Digestion: INTESTINE

  2. Duodenum: completion of digestion

  3. In the duodenum final digestion of all foods takes place. • Acidic chyme coming in from the stomach is now neutralized and further digested with new enzymes.

  4. By peristalsis of the stomach’s smooth muscle the chyme flows through the pyloricsphincter into the duodenum.

  5. The duodenal epithelium produces two hormones, secretin and cholecystokinin (CCK), whose job is to “switch off” the stomach, and stimulate the release of bile and pancreatic juices. • In addition, the epithelium of the duodenum produces a few digestiveenzymes that finish off the job!

  6. LIVER SPLEEN GALLBLADDER PANCREASDUODENUM STOMACH KIDNEY

  7. LIVER(prefix: hepato) • Largest internal organ. • Largest blood reserve. • Over 200 metabolic functions, including... • storage of glucose (as glycogen), fats and minerals. • removal of wastes and toxins. • filtration of blood, recycling of Fe and removal of old RBCs. • production and storage of lipid-emulsifying bile salts.

  8. Main cells: hepatocytes

  9. Served by the hepaticartery and the hepaticportalvein, drained by the hepaticvein.

  10. The Hepatic Portal System

  11. Bile (also called bile salts) is a fluid produced by the liver that emulsifies lipids. It is produced in the liver and stored in the gallbladder.

  12. In response to CCK bile travels down the cysticduct, then into the commonbileduct, and finally enters the duodenum via the AmpullaofVater.

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  14. Liver Gallbladder Bile Stomach Secretinand CCK – Gastrin + CCK + Pancreas Duodenum ofsmall intestine Secretin + Key StimulationInhibition CCK + + –

  15. Gallstones are hard masses of crystallized bile that form in the gallbladder as a result of changes in the composition of bile (usually caused by too fatty a diet). Can block ducts, causing severe pain that requires surgery.

  16. Chinese bile farming with moon bears.

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  18. Pancreas • A long, lumpy, soft & easily broken organ. • Shared with the endocrinesystem (makes insulin & glucagon).

  19. In response to the hormone cholecystokinin (CCK) the pancreas produces pancreaticenzymes essential for digestion. • In response to the hormone secretin the pancreas produces buffers and bicarbonates that neutralize the acidity in chyme. • Neutralizing fluids and enzymes combined make the pancreatic juice, which enters the duodenum via the Ampulla of Vater (seen previously).

  20. Liver Gallbladder Bile Stomach Secretinand CCK – Gastrin + CCK + Pancreas Duodenum ofsmall intestine Secretin + Key StimulationInhibition CCK + + –

  21. Three hormones are involved in digestion. • Gastrin is secreted mainly by the G cells in the gastric glands in response to the sight, scent or thought of food. Preps the stomach by stimulating chief & parietal cells to release gastric juices). • Secretin is secreted by the epithelium of the duodenum in response to acidic chyme. Stimulates the pancreas to release pancreaticjuice (which contains bicarbonate, an acid neutralizer). It also acts on G cells inhibiting gastrin production. • Cholecystokinin (CCK) is also secreted by the epithelium of the duodenum in response to acidic chyme. It stimulates the gallbladder to releasebilesalts and stimulates the pancreas to produce pancreatic enzymes. Also acts on G cells inhibiting gastrin production.

  22. DIGESTIVE ENZYMES! The simple form! Nucleases absent!

  23. Carbohydrate digestion Protein digestion Nucleic acid digestion Fat digestion Disaccharides Polysaccharides (starch, glycogen) (sucrose, lactose) Mouth Salivary amylase Smaller polysaccharides,maltose Stomach Proteins Pepsin Small proteins DNA, RNA Fat globules Small proteins Polysaccharides Lumen ofsmall intes-tine Pancreatic amylases Pancreatic trypsin andchymotrypsin Pancreatic nucleases Bile salts Maltose and otherdisaccharides Fat droplets Nucleotides Smallpeptides Pancreatic lipase Peptidases Glycerol, fattyacids, monoglycerides Amino acids Epitheliumof smallintestine Small peptides Nucleotidases Nucleosides Disaccharidases Peptidases Nucleosidasesandphosphatases Nitrogenous bases,sugars, phosphates Monosaccharides Amino acids

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