Physiology Of The Stomach 2 Flashcards
Question: What processes result from the contraction and relaxation of the layers of muscle in the stomach wall?
Answer: Gastric motility involves the actions of grinding, churning, kneading, twisting, and propelling contents within the stomach.
Question: What is responsible for coordinating gastric motility?
Answer: Gastric motility is coordinated by the Myenteric plexus, which receives input from the Autonomic Nervous System (ANS).
Question: How does parasympathetic stimulation affect gastric motility?
Answer: Parasympathetic stimulation increases gastric motility.
Question: What is the impact of sympathetic stimulation on gastric motility?
Answer: Sympathetic stimulation decreases gastric motility.
Question: How does the Muscularis contribute to mechanical digestion in the stomach?]
Answer: The Muscularis enables food to be churned, especially in the antrum where the muscle wall is thicker, resulting in more powerful contractions.
Question: What is the outcome of the mixing of food with gastric juice in the stomach?
Answer: The mixing of food with gastric juice in the stomach produces a semi-liquid substance called chyme.
Question: Through which structure does chyme pass from the stomach to the duodenum?
Answer: Chyme passes through the pyloric sphincter to reach the duodenum.
Question: What enzyme is responsible for breaking down proteins in the stomach?
Answer: Pepsin is the enzyme responsible for breaking down proteins in the stomach.
Question: Under what conditions is pepsin active?
Answer: Pepsin is only active in an acidic environment.
Question: How is pepsinogen converted into pepsin?
Answer: Pepsinogen is converted into pepsin by the action of hydrochloric acid (HCl).
Question: Which enzyme facilitates the breakdown of fat in the stomach, and at what pH is it active?
Answer: Gastric lipase facilitates the breakdown of fat, and it is active at a higher pH (5-6).
Question: Why is the initiation of fat digestion important, particularly in infants?
Answer: The initiation of fat digestion, facilitated by gastric lipase, is crucial for the digestion of breast milk in infants.
Question: What initiates protein digestion in the stomach?
Answer: Gastric pepsins initiate protein digestion in the stomach.
Question: What are the products of pepsin hydrolyzing proteins, and what is their role?
Answer: Pepsin hydrolyzes proteins into polypeptides and amino acids, which further stimulate acid production
Question: At what pH is pepsin inactivated, and how can it be re-activated?
Answer: Pepsin is inactivated at a higher pH, above approximately pH 6, but can be re-activated upon re-acidification.
Question: How does the acidic environment of the stomach affect the activity of salivary amylase?
Answer: Salivary amylase, which acts on carbohydrates, is far less active in the acidic environment of the stomach due to gastric pH.
Question: What determines the force of contraction and the amount of gastric emptying in the stomach?
Answer: The force of contraction and amount of gastric emptying are determined by neuronal and hormonal input to the antral smooth muscle.
Question: What factors influence the rate of gastric emptying?
Answer: The rate of gastric emptying is influenced by the physical and chemical nature of the contents of the stomach and intestine.
Question: How does distension of the stomach impact antral contraction?
Answer: Distension of the stomach increases antral contraction.
Question: What effect does increased gastrin levels have on antral contraction?
Answer: Increased gastrin levels also increase antral contraction.
Question: List the three main processes involved in stomach emptying.
Answer: Stomach emptying involves constriction of the lower esophageal sphincter, contraction of the gastric muscularis, and relaxation of the pyloric sphincter.
Question: What inhibits gastric emptying, and what is this phenomenon called?
Answer: Gastric emptying is inhibited by the distension of the duodenum, the presence of fat, or increased hydrochloric acid ([HCl]). This is known as the ‘enterogastric reflex.’
Question: What is the purpose of the enterogastric reflex?
Answer: The enterogastric reflex prevents excessive chyme from entering the duodenum all at once, aiding in digestion and absorption.
Question: How does the regulation of gastric emptying impact oral drug absorption?
Answer: The rate of gastric emptying, influenced by factors like the presence of fat, can have implications for oral drug absorption. For example, a high-fat meal may delay the entry of substances into the duodenum.
Question: How does the fat content in a meal influence gastric emptying?
Answer: Different meal components empty at different rates, and higher fat content can slow gastric emptying.
Question: How does the size of a meal affect the digestive phase?
Answer: Larger amounts of food result in a longer digestive phase.
Question: Describe the pattern of gastric emptying for larger meals.
Answer: Larger amounts of food tend to empty slowly initially and then more quickly. This prolonged time in the stomach ensures adequate exposure to gastric secretions.
Question: What role does nutrition density, particularly calories, play in controlling or slowing gastric emptying?
Answer: Nutrition density, especially the calorie content, controls and can slow gastric emptying.
Question: What are other factors that influence gastric emptying?
Answer:
- Composition of food
- Posture
- Volume
- Temperature
- Pregnancy
- Conditions such as migraine, gastric ulcer, pernicious anaemia
- Other factors such as drugs, e.g. alcohol, anticholinergics…
Question: What substances are absorbed from the stomach?
Answer: Water, electrolytes, alcohol, and some drugs can be absorbed from the stomach.
Question: Is the stomach wall generally permeable to most materials?
Answer: No, the stomach wall is generally impermeable to most materials.
Question: When does proper absorption of nutrients begin, and where does it occur?
Answer: Proper absorption of nutrients begins when contents reach the small intestine, where they are acted upon by products of the pancreas, liver, and gallbladder.
Question: What is a major source of variability in the gastric absorption of drugs?
Answer: The presence of food in the stomach is a major source of variability in the gastric absorption of drugs.
Question: How can the rate of gastric emptying influence the onset of drug absorption via the small intestine?
Answer: The rate at which gastric emptying occurs can be a controlling factor in the onset of drug absorption through the small intestine.
Question: Is the effect of food on the behavior of a particular drug formulation predictable?
Answer: The specific effect of food on the behavior of a particular drug formulation is unpredictable.
Question: What contributes to significant variability in diet across populations?
Answer: Significant population variability in diet contributes to the unpredictable effects of food on drug absorption.
Question: How can oral formulations be designed to take advantage of gastric emptying and motility patterns?
Answer: Oral formulations can be designed to take advantage of gastric emptying and motility patterns, optimizing drug absorption.
Question: Define an ulcer.
Answer: An ulcer is the erosion of the mucosal layer, resulting in inflammation and damage to underlying tissue.
Question: What is the primary cause of damage in an ulcer, and is acid always the initial damaging feature?
Answer: While acid is not necessarily the initial damaging feature, an ulcer involves the erosion of the mucosal layer, leading to inflammation and damage to underlying tissue.
Question: What were some historical beliefs regarding the causes of ulcers?
Answer: Historically, ulcers were thought to be linked to stress and excess acid.
Question: Where does gastric ulceration typically occur in the gastrointestinal (GI) tract?
Answer: Gastric ulceration occurs acutely or chronically in the GI tract, often in close proximity to acid-producing cells.
Question: What percentage of duodenal ulcers and gastric ulcers are associated with H. pylori infection?
Answer: Approximately 95% of duodenal ulcers and 85% of gastric ulcers are associated with H. pylori infection.
Question: What is the primary cause of the remaining ulcers not associated with H. pylori?
Answer: The remaining ulcers are primarily attributed to the use of nonsteroidal anti-inflammatory drugs (NSAIDs).
Question: Is there consensus on the synergistic effect between H. pylori infection and NSAID use in causing ulcers?
Answer: There is controversy over whether there is synergism between H. pylori infection and NSAID use in causing ulcers.
Question: Name some additional factors that may contribute to gastric ulceration.
Answer: Factors such as smoking, caffeine, alcohol, and stress may contribute to gastric ulceration.
Question: What are the key components of the management of gastric ulceration?
Answer: The management of gastric ulceration involves explanation and reassurance, dietary control, drug therapy, and maintaining the balance between damaging and protective factors of the intestinal mucosa.
Question: What is the primary focus of drug therapy in gastric ulcer management?
Answer: Drug therapy aims at controlling acid production to maintain the balance between damaging and protective factors of the intestinal mucosa.
Question: What specific action is taken regarding H. pylori in the management of gastric ulcers?
Answer: Eradication of H. pylori is a specific measure taken in the management of gastric ulcers.
