Digestive System

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Digestive System

• Pancreas Large Intestine

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Pancreas (accessory)

• Location
• Pancreatic duct
• Islets

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Pancreas

• Pancreatic Juice
• Acinar Cells exocrine
• Bicarbonate
• Pancreatic Amylase

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Pancreas

• Protein Enzymes
• Trypsin
• Chymotrypsin
• Carboxypolypeptidase
• Lipase

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Controls of Juice Release

• Secretin
• Cholecystokinin
• Neurally Vagus nerve stimulates release

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Liver (accessory)

• Hepato-
• 4 lobes Falciform ligament separates large R L
  lobes
• Cells are hepatocytes
• Common Bile Duct (Hepatic duct Gall bladder
  duct), which empties into duodenum

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Liver

• Blood supply enormous
• Bile Production
• 600-1000 mls per day
• Liver cells make bile, gall bladder STORES bile

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Bile Composition

• Water
• Bilirubin (from Hb breakdown)
• Bile Salts function in Emulsification

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Enterohepatic Circulation

• Bile salts secreted into duodenum, are reabsorbed
  in ileum and returned to liver

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Bile Secretion Controls

• Enterohepatic Circulation
• Vagus Nerve
• Secretin
• Increased hepatic blood flow
• Cholecystokinin

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More liver functions

• Metabolic regulation (blood filtering, monitoring
  blood)
• Clotting factors are made by liver
• Blood protein synthesis
• Phagocytosis of old WBC RBCs
• Detoxification, storage of toxins
• Stores glucose (glycogen), fat, protein, Cu, Fe,
  Vitamins

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SUMMARY of GI HORMONES

• GASTRIN
• Made by pylorus cells
• Increases gastric motility
• Increases gastric secretions

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SUMMARY of GI HORMONES

• SECRETIN
• Made by duodenal cells
• Decreases gastric motility secretions
• Increases pancreatic juice release
• Increases bile secretion

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SUMMARY of GI HORMONES

• CHOLECYSTOKININ
• Made by duodenal cells
• Decreases gastric motility secretions
• Increases pancreatic juice release
• Increases gall bladder contraction

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SUMMARY of GI HORMONES

• GIP (Gastric Inhibitory Peptide)
• Made by duodenal cells
• Decreases gastric motility secretions
• Promotes insulin release

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Small Intestine

• 21 foot tube
• Duodenum 1 foot
• Jejunum 8 ft.
• Ileum 12 ft.

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Small Intestine Microstructure

• Villi
• Microvilli
• Blood vessels
• Lacteals

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Small Intestinal Secretions

• 2-3 liters of juice per day
• Duodenal glands (Brunners) make protective mucus
• Intestinal glands make isotonic fluid containing
  some digestive enzymes

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Small Intestine Motility

• Segmentation
• Peristalsis

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Absorption

• Definition 90 of all absorption occurs in SI
• Nutrients from SI to blood or lymph vessel
• Villi Microvilli
• Processes include active transport, diffusion,
  facilitated diffusion, cotransport

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Absorption

• Carbohydrates
• Proteins
• Lipids
• Emulsification
• Lipase
• Micelles (fat bile salt)
• Chylomicrons
• Lacteals

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Absorption

• Vitamins (ADEK along with fat, Bs and C along
  with water)

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Absorption

• Water Electrolytes (ions in soln.)
• 9 liters/day by osmosis
• Sodium
• Calcium absorption is Vit. D dependent

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Large Intestine

• Five feet long
• Cecum
• Ileocecal sphincter valve
• Appendix

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Large Intestine

• Colon
• Ascending
• Transverse
• Descending
• Sigmoid
• Rectum
• Anus

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Large Intestine

• No villi
• Goblet cells make mucus
• Taeniae coli flat muscular bands
• Haustra pouches as taeniae coli contract

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Large Intestine Motility

• Peristalsis
• Haustral churning
• Mass peristalsis drives contents into rectum
• Gastroileal reflex activates mass peristalsis
• Defecation reflex
• Anal sphincters Internal and External

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Large Intestine Functions

• Some water absorption
• Lubrication of contents
• Form and store feces
• Synthesis of Vitamin K and some B vitamins and
  absorption
• Bacterial fermentation

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