1. 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

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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)

8. Enzymatic Digestion of Carbohydrates
Enzyme
Source
Substrate
Product
Amylase
Salivary glands
Pancreas
Starches
Amylose
Maltose
Dextrins
Dextrinase
Brush Border cells
Glucose
Maltase
Sucrase
Sucrose
Fructose
Lactase
Lactose
Galactose

9. Enzymatic Digestion of Lipids
Enzyme
Source
Substrate
Product
Lipase
Tongue
(Lingual)
Triglycerides
Fatty acids
monoglycerides
Stomach
(gastric)
Milk butterfats
Pancreas
(pancreatic)

10. Enzymatic Digestion of Proteins
Enzyme
Source
Substrate
Product
Pepsin
Pepsinogen
(HCl)
Chief
Cells
Proteins
Peptides
Amino acids
Trypsin
Trypsinogen
(enterokinase)
Acinar
Chymotrypsin
Chymotrypsinogen
(Trypsin)

11. Enzymatic Digestion of Proteins
Enzyme
Source
Substrate
Product
Elastase
Proelastase
(Trypsin)
Acinar
Cells
Proteins
Peptides amino acids
Carboxypeptidase
Procarboxypeptidase
Acinar cells
Terminal AA on the carboxyl end
Amino acids
Enterokinase
Brush Border
Trypsinogen
Trypsin

12. Enzymatic Digestion of Proteins
Enzyme
Source
Substrate
Product
Aminopeptidase
Brush Border
Terminal AA at the amino end
Amino acids
Dipeptidase
Dipeptides
Amino Acids

13. Enzymatic Digestion of nucleic Acids
Enzyme
Source
Substrate
Product
Ribonuclease
Acinar
Cells
Ribonucleic acids
Nucleotides
(A, G,, C, or U)
Deoxyribonuclease
Deoxyribo-
nucleic acid
(A, G, T, C)
Nucleosidases
Brush
Border
Nitrogenous
Bases, pentoses,
phosphates