Hormones and Digestion
• Gastrin
o Secreted by the G-cells in the antrum of the stomach
o Stimulates parietal cells to secrete HCl
• Secretin – released because of acid in duodenum
o Stimulates pancreas to secrete fluid and bicarbonate into the gut
• Cholecystokinin (CCK) - Fats and(or) proteins entering the SI stimulate the
release of CCK
o Causes pancreas to secrete digestive enzymes
o Stimulates gall bladder to release bile salts
• Leptin
o Insulin causes secretion
o Secreted from adipocytes
o Acts on hypothalamic leptin receptors to inhibit feed intake
o Increases energy expenditure
GI Tract Secretions
|
Source |
Secretion |
Species |
Substrate(Function) |
|
Mouth |
S. Amylase |
Pig, man |
Glycogen, starch, dextrin |
|
Mucin |
All |
Lubrication |
|
|
Pregast. esterase |
Young Ruminant |
Fat - milk fat |
|
|
Stomach |
Pepsin |
All |
Protein |
|
HCl |
All |
Activate pepsin (protein) |
|
|
Lipase |
All |
Fats |
|
|
Mucin |
All |
Protection & lubrication |
|
|
Rennin |
Young Ruminant |
Milk protein (casein) |
|
|
Intrinsic factor |
All |
Vit. B12 absorption |
|
|
Mucin (pyloric) |
All |
Protection & lubrication |
|
|
Pancreas |
Amylase |
All |
Starch |
|
Sucrase |
All |
Sucrose |
|
|
Trypsin |
All |
Protein, peptides |
|
|
Chymotripsin |
All |
Protein, peptides |
|
|
Carboxypeptidase |
All |
Protein, peptides |
|
|
Lipase |
All |
Fats |
|
|
Liver |
Bile |
All |
Fat emulsification |
|
S.I. |
Enterokinase |
All |
Trypsinogen activation |
|
Aminopeptidase |
All |
Protein |
|
|
Dipeptidase |
All |
Dipeptides |
|
|
Nucleotidase |
All |
Nucleotides |
|
|
Nucleosidase |
All |
Nucleosides |
|
|
Alkaline Phosphatase |
All |
Organic phosphates |
|
|
Lipase |
All |
Fat |
|
|
Maltase |
All |
Maltase |
|
|
Lactase |
All (Avian) |
Lactose |
|
|
Sucrase |
All |
Sucrose |
|
|
L.I. |
Mucin |
All |
Protection & lubrication |