Terms in this set (17)
What are the components of gastric juice?
pepsin, amino acids, pepsinogen
What specialized stomach cells secrete gastric juice?
- chief cells and parietal cells
What is the function of hydrochloric acid (HCl) in the stomach?
- HCL functions to denature proteins (cause them to unravel) - it causes the tissues to fall apart and thus the food becomes solubilized
What is the function of pepsin in the stomach?
- catalyzes the breakdown of proteins into smaller units called amino acids
What catalyzes the conversion of pepsinogen to pepsin in the stomach?
- chief cells secrete an inactive form of pepsin, which is pepsinogen
- pepsinogen is converted to the active pepsin only when it leaves the gastric pits and enters the acid environment of the stomach
What is the function of alkaline mucus that coats the stomach wall?
- functions to protext the epithelium from the destructive effects of hydrochloric acid and pepsin
- acid near the epithelium becomes neutralized and pepsin near the epithelium become inactivated
What are the major causes of peptic ulcers?
- oversecretion of hydrochloric acid - overwhelms the protective mucus lining
- a breakdown of the mucus barrier
- helicobacter pylori
What are the treatments for peptic ulcers?
- stress reuction
- certain foods that strongly stimulate the secretion of HCl should be avoided
- frequent feeding ensures that HCl is always digesting food rather than digesting an empty stomach
- there are many drugs (Zantac, Pepcid AC) that act to reduct the production of HCl
- antibiotics that inhibit the growth of H. pylori
What is chyme?
- in the stomach, food is converted from a solid to a semi-liquid paste
- semi-liquid paste is chyme
What factors influence the rate of at which the stomach empties its contents into the small intestine?
- the fluidity of the food consumed
- the amount of fat present in the food
Name the 3 phases in the regulation of gastric function.
- cephalic phase
- gastric phase
- intestinal phase
What happens in cephalic phase?
- the smell, taste, or even thought of food can stimulate secretion of saliva and gastric juice which is stimulated by the vagus nerve
- stimulates secretion of HCl from parietal cells and pepsinogen
What happens in gastric phase?
presence of food in stomach stimulates secretion of HCl and pepsinogen
What happens in intestinal phase?
- slows the rate of gastric emptying in response to chime in the duodenum
- initiates a neural reflex that decreases gastric secretion and motility
How does the hormone Gastrin affect the secretion of HCL?
- gastrin stimulates the secretion of more HCl and pepsinogen, which leads to more protein breakdown, which in turn leads to even more gastrin secretion
What effect does the presence of food in the mouth have on secretion of pepsinogen?
- stimulates the secretion from the vagus nerve
Does the movement of chime from the stomach to the small intestine speed up or slow down gastric emptying?
- slow down
- when fat-containing chime enters the duodenum, further gastric emptying is prohibited until the small intestine has processed the fat already there
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