Hormonal control in the Digestive system: Gastric hormones

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Hormonal control in the Digestive system Gastric
hormones

• GASTRIN
• Secretion By enteroendocrine (G) cells in
  gastric pits of the mucosa.
• Stimulus Stomach distention and acid pH of
  chyme causes Gastrin.
• Action
• 1. increases HCl production in stomach
• 2. increases gastric motility
• 3. stimulates growth of gastric mucosa
• 4. contract lower esophageal sphincter
• 5. relaxes pyloric sphincter
• 6. relaxes ileocecal sphincter

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Hormonal control in the Digestive system Gastric
hormones

• Somatostatin
• Secretion By enteroendocrine (D) cells in
  gastric pits of the mucosa in the pylorus.
• Stimulus continuously released, overridden by
  Gastrin and nerves
• Action
• Inhibition of Gastrin production

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Hormonal control in the Digestive system Small
Intestinal hormones

• SECRETIN
• Secretion By Enteroendocrine (S) cells in the
  Crypts of Lieberkuhn of small intestine.
• Stimulus Acid chyme in small intestine causes
  secretion of Secretin
• Actions
• stimulate secretion of pancreatic juice and bile
  that is rich in bicarbonate ions.
• inhibit production of HCl in stomach
• promote growth and maintenance of the pancreas
• enhance effects of Cholecystokinin (CCK)
• Increases rate of bile secretion by hepatocytes

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Hormonal control in the Digestive system small
intestinal hormones

• CHOLECYSTOKININ (CCK)
• Secretion Enteroendocrine (CCK) cells in the
  small intestine mucosa Crypts of Lieberkuhn
• Stimulus Chyme rich in amino acids,
  triglycerides and fatty acids enter the small
  intestine.
• Actions
• increases secretion of pancreatic juice rich in
  digestive enzymes
• opens the Sphincter of Oddi
• contracts the gallbladder
• Inhibits gastric secretion and motility
• May reduce hunger

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Hormonal control in the Digestive system small
intestinal hormones

• Gastric Inhibitory Peptide (GIP)
• Secretion Enteroendocrine cells in the small
  intestine mucosa Crypts of Lieberkuhn
• Stimulus Chyme rich in triglycerides, fatty
  acids, and glucose enter the small intestine.
• Actions
• Stimulates release of insulin by beta cells
• Inhibits gastric secretion and motility
• Stimulates lipogenesis by adipose tissue
• Stimulates glucose use by skeletal muscle cells

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Hormonal control in the Digestive system small
intestinal hormones

• Vasoactive Intestinal Peptide (VIP)
• Secretion Enteroendocrine cells in the small
  intestine mucosa Crypts of Lieberkuhn
• Stimulus Chyme entering the small intestine.
• Actions
• Stimulates buffer secretion
• Inhibits gastric secretion
• Dilates intestinal capillaries

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Hormonal control in the Digestive system Pancreas
and Islets of Langerhans

• Endocrine cells make up 1 of the pancreas and
  are observed as Islets of Langerhans
• 1. Alpha Cells Secrete Glucagon (increases
  blood sugar)
• 2. Beta Cells Secrete Insulin (decreases blood
  sugar)
• 3. Delta Cells Secrete Human Growth
  Hormone- Inhibiting Hormone (inhibit secretion of
  both glucagon and insulin and slows rate of
  nutrient absorption)
• 4. F-Cells Secrete Pancreatic Polypeptide
  (inhibit secretion of digestive enzymes and
  inhibits contraction of the gallbladder)

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Enzymatic Digestion of Carbohydrates
Enzyme Source Substrate Product
Amylase Salivary glands Pancreas Starches Amylose Maltose Dextrins
Dextrinase Brush Border cells Dextrins Glucose
Maltase Brush Border cells Maltose Glucose
Sucrase Brush Border cells Sucrose Glucose Fructose
Lactase Brush Border cells Lactose Glucose Galactose
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Enzymatic Digestion of Lipids
Enzyme Source Substrate Product
Lipase Tongue (Lingual) Triglycerides Fatty acids monoglycerides
Lipase Stomach (gastric) Milk butterfats Fatty acids monoglycerides
Lipase Pancreas (pancreatic) Triglycerides Fatty acids monoglycerides
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Enzymatic Digestion of Proteins
Enzyme Source Substrate Product
Pepsin Pepsinogen (HCl) Chief Cells Proteins Peptides Amino acids
Trypsin Trypsinogen (enterokinase) Acinar Cells Proteins Peptides Amino acids
Chymotrypsin Chymotrypsinogen (Trypsin) Acinar Cells Proteins Peptides Amino acids
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Enzymatic Digestion of Proteins
Enzyme Source Substrate Product
Elastase Proelastase (Trypsin) Acinar Cells Proteins Peptides amino acids
Carboxypeptidase Procarboxypeptidase (Trypsin) Acinar cells Terminal AA on the carboxyl end Amino acids
Enterokinase Brush Border Trypsinogen Trypsin
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Enzymatic Digestion of Proteins
Enzyme Source Substrate Product
Aminopeptidase Brush Border Terminal AA at the amino end Amino acids
Dipeptidase Brush Border Dipeptides Amino Acids
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Enzymatic Digestion of nucleic Acids
Enzyme Source Substrate Product
Ribonuclease Acinar Cells Ribonucleic acids Nucleotides (A, G,, C, or U)
Deoxyribonuclease Acinar Cells Deoxyribo- nucleic acid Nucleotides (A, G, T, C)
Nucleosidases Brush Border Nucleotides Nitrogenous Bases, pentoses, phosphates
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