B2 Structure and Function of the Upper GI Tract Flashcards
What is the function of stomach acid?
Sterilises food to prevent food poisoning
Optimal pH for the function of gastric enzymes
How do H pylori bacteria survive in the stomach (acidic conditions)
H. pylori increase enzyme that causes the breakdown of urea. This produces ammonia which neutralises the acid and enables the bacteria to survive
What do Chief cells do and then what happens to their secretion?
Release pepsinogens that are activated by the acidic conditions to pepsins. The pepsins are autocatalytic- the new pepsin chops up pepsinogens
What are pepsins/what do they do?
Chop up proteins into polypeptides (proteolysis)
What are the three stages of acid secretion?
- Cephalic Phase
- Gastric Phase
- Intestinal Phase
What is the cephalic phase?
Phase of acid secretion
starts the process, ACh causes release of gastric acid.
Parasympathetic anticipation causes stimulation
What is the gastric phase?
Main control of acid secretion
Local ACh release causes further gastric acid secretion
Release of NT Histamine stimulates acid secretion ]
Gastrin also released
Mucus is secreted to protect the stomach
What is the intestinal phase?
Inhibitory pathway - stops pepsin and acid secretion
Negative and positive feedback system to control acidity level e.g. further secretion of gastrin
What role does the duodenum play?
Secreted bicarbonate that neutralises stomach acid and reduces pepsinogen
Secretion of bile emulsifies fat before lipase breaks down
What is stomach and instrinsic factor?
Vitamin B12 binds to intrinsic factor? and transports to the duodenum where it is absorbed. Intrinsic factor promotes B12 absorption.
Signs of stomach cancer
May present with dyspepsia, gastric bleeding, weight loss, abdominal masses
