Small intestine physiology Flashcards
What are the secretions of the duodenum?
Gastrin Secretin Cholecystokinin Motilin Glucagon-like insulinotropic peptide Glucagon-like peptide 1
What will enhance secretion from the small intestine?
Cholecystokinin Secretin Distention/irritation Parasympathetic stimulation Gastrin
What does secretion from the small intestine contain?
Mucus – for protection/lubrication (from goblet cells)
Aqueous salt - for enzymatic digestion (mostly from the crypts)
How is segmentation/mixing in the small intestine achieved by the muscles?
Intermittent contraction and relaxation of the circular muscles creates a chopping motion
What is the movement of segmentation initiated by?
The pacemaker cells of the intestine - they control the BER which is continuous
Must reach threshold potential to cause segmentation
What causes the BER to reach threshold potential in the small intestine to initiate segmentation?
Distention of the small intestine by entering chyme
What is segmentation in the empty ileum triggered by?
Gastrin from the stomach
Gastroileal reflex
What is the migrating motor complex of the small intestine?
Strong peristaltic wave occurring every 90-120 minutes to clear the small intestine - “housekeeper function”
What triggers the migrating motor complex of the small intestine?
Motilin
What suppresses the migrating motor complex of the small intestine?
Feeding
Vagal activity
Gastrin
Cholecystokinin
What digestive enzymes are secreted by the pancreas?
Proteases - trypsinogen, chymotrypsinogen, procarboxypeptidase
Amylase - pancreatic amylase
Lipase - pancreatic lipase
What is the purpose of the pancreas secreting bicarbonate rich fluid?
Neutralises acidic chyme from the stomach
Provides optimum pH for pancreatic enzyme function
Protects mucosa from erosion by acid
Which duodenal secretion is increased in response to acid in the duodenal lumen?
Secretin - promotes the secretion of alkaline solution from the pancreatic duct cells to neutralise the acid
Which duodenal secretion is increased in response to fat and protein in the duodenal lumen?
CCK - promotes the secretion of digestive enzymes from the acinar cells of the pancreas
What special glands does the duodenum contain and what are their functions?
Contain Brunner’s glands in the submucosa
Produce a mucous rich alkaline secretion (containing bicarbonate)
