Digestive Physiology Flashcards
What 2 nerve plexuses modulate digestive tract activity?
-Myenteric (Auerbach’s) between muscle layers
-Submucosal (Meissner’s) plexus
What cells initiate slow wave potentials?
Cells of Cajal
What enzymes are utilized in the mouth?
Salivary amylase: carbohydrates
Lingual lipase: lipids
What stomach factors determine how fast the stomach empties (gastric emptying) its contents?
-Volume of chyme=distends of smooth muscle increases emptying
-Nervous (vagus nerve) and hormonal (gastrin) influence=increases emptying
-Fluidity of chyme=level of fluidity must be achieved for emptying=increased fluidity=increased emptying
What duodenum factors halt gastric emptying?
Fat, acid, hypertonicity, & distension all halt emptying = decrease antral peristaltic
activity via both nerve & hormones
These factors will activate appropriate neural or hormonal responses to halt emptying
A. Intrinsic nerves (short reflex) and ANS (long reflex)
B. Enterogastrones from duodenum carried to stomach via blood
What hormones are involved inhibiting gastric emptying?
Secretin
Cholecystokinin (CCK)
Gastric inhibitory peptide (GIP)
What 3 cell types are found in the gastric pits of the fundus & body? What do they secrete?
-Mucous neck cells secrete mucus
-Chief cells secrete pepsinogen
-Parietal (oxyntic) cells secrete HCl and intrinsic factor
What cell in the stomach secretes gastrin?
G cells secrete gastrin into the blood
What is the function of enterokinase?
Brush border enzyme
Activates trypsinogen into trypsin
Name all the enzymes secreted by the pancreas
-Trypsinogen
-Autocatalytic
-Chymotrypsin
-Carboxypeptidase
-Pancreatic amylase=carb digestion
-Pancreatic lipase=lipid digestion
What is the function of the gall bladder?
Stores and concentrates bile between meals
What is the function of bile?
-Detergent action on large fat globules produces smaller droplets which increase the surface area for lipid digestion by lipase
-Along with cholesterol and lecithin, they form micelles which transport lipid soluble molecules to the mucosa
What hormones are involved in regulating pancreatic secretions? What stimuli do these hormones react most to?
-Hormonally regulated with a small amount of parasympathetic influence
-Secretin release in response to acid in duodenum
-Stimulates pancreatic duct cells to increase alkaline solution secretion
-Cholecystokinin (CCK) release in response to fat (primarily) and protein in duodenum
-Stimulates acinar cells to increase digestive enzyme secretion
What are brush border enzymes?
-Complete protein and carbohydrate digestion
-Enterokinase: activation of trypsinogen
-Disaccharidases: maltase, sucrase, lactase
-Aminopeptidases
What is the function of having villi and microvilli in the small intestine?
Increased surface area
