Physiology Of The Stomach 1

Question 1

Question: What is the primary function of the stomach in terms of food storage?

Answer 1

Answer: The stomach serves as a temporary storage organ for food.

Question 2

Question: How does the stomach contribute to mechanical digestion?

Answer 2

Answer: The stomach facilitates mechanical digestion through its rhythmic movements.

Question 3

Question: Which type of digestion occurs in the stomach, specifically targeting proteins?

Answer 3

Answer: Chemical digestion of proteins takes place in the stomach.

Question 4

Question: What role does the stomach play in regulating the passage of chyme into the small intestine?

Answer 4

Answer: The stomach regulates the passage of chyme, controlling the flow into the small intestine.

Question 5

Question: What is the significance of intrinsic factor secreted by the stomach?

Answer 5

Answer: Intrinsic factor, secreted by the stomach, is essential for the absorption of vitamin B12.

Question 6

Question: How does the muscularis in the stomach contribute to mechanical digestion?

Answer 6

Answer: The muscularis in the stomach enables the churning of food, especially in the antrum where the muscle wall is thicker, leading to more powerful contractions.

Question 7

Question: What is the result of mixing food with gastric juice in the stomach?

Answer 7

Answer: The mixing of food with gastric juice in the stomach produces chyme.

Question 8

Question: Through which structure does chyme pass from the stomach to the duodenum?

Answer 8

Answer: Chyme passes through the pyloric sphincter to reach the duodenum.

Question 9

Question: What are the three key types of cells in the gastric glands responsible for producing gastric juices?

Answer 9

Answer: The three key types of cells in the gastric glands are zymogenic (chief/peptic) cells, parietal (oxyntic) cells, and goblet (neck) cells.

Question 10

Question: What is the primary secretion of zymogenic (chief/peptic) cells in the gastric glands?

Answer 10

Answer: Zymogenic cells secrete pepsinogen.

Question 11

Question: What is the primary secretion of parietal (oxyntic) cells in the gastric glands, and what additional substance do they secrete?

Answer 11

Answer: Parietal cells secrete HCl (hydrochloric acid) and intrinsic factor.

Question 12

Question: What is the primary secretion of goblet (neck) cells in the gastric glands?

Answer 12

Answer: Goblet cells secrete mucous

Question 13

Question: What is the primary secretion of G cells in the gastric glands?

Answer 13

Answer: G cells secrete gastrin.

Question 14

Question: What substance is primarily secreted by enterochromaffin (mast-like) cells in the gastric glands?

Answer 14

Answer: Enterochromaffin cells secrete histamine.

Question 15

Question: What is the primary secretion of D cells in the gastric glands?

Answer 15

Answer: D cells secrete somatostatin.

Question 16

Question: Which enzyme is responsible for breaking down proteins in the stomach?

Answer 16

Answer: Pepsin is the enzyme responsible for breaking down proteins in the stomach.

Question 17

Question: Under what conditions is pepsin active in the stomach?

Answer 17

Answer: Pepsin is only active in an acidic environment.

Question 18

Question: How is pepsinogen converted into pepsin in the stomach?

Answer 18

Answer: Pepsinogen is converted into pepsin by the action of hydrochloric acid (HCl).

Question 19

Question: What is the role of gastric lipase in fat digestion, and at what pH does it function optimally?

Answer 19

Answer: Gastric lipase breaks down fat in the stomach, and it functions optimally at a higher pH (5-6).

Question 20

Question: In what context does the stomach play an important role in lipid digestion in infants?

Answer 20

Answer: The stomach plays an important role in lipid digestion in infants from breast milk, providing limited initiation of fat digestion.

Question 21

Explain this diagram on the formation of stomach acid.

Answer 21

The release of stomach acid occurs primarily in the presence of food in the stomach.

The diagram shows parietal cells and they contain protein pumps which transport H+ ions from the cytoplasm of the cell into the stomach lumen. Cl- ions are also transported across the parietal cell into the stomach lumen, it then combines with H+ to produce HCl.

The production of H2CO3 is unstable which leads to a split producing HCO3- + H+. HCO3- moves into the stomach lumen. HCO3- and mucous protect the stomach lining from excess stomach acid and HCO3- helps neutralise any excess acid the comes into contact with the lining of the stomach.

Question 22

Question: What prevents the stomach from digesting itself despite the presence of gastric juices?

Answer 22

Answer: The mucosal barrier prevents the stomach from digesting itself.

Question 23

Question: How do tight junctions between mucosal epithelial cells contribute to the protection of the stomach?

Answer 23

Answer: Tight junctions prevent the leakage of gastric juice onto underlying tissue, contributing to the protection of the stomach.

Question 24

Question: What is the role of mucous secreted by epithelial/goblet cells in the stomach’s self-protection mechanism?

Answer 24

Answer: Mucous secreted by epithelial/goblet cells has a higher pH, providing localized neutralization and serving as a physical barrier to acid.

Question 25

Question: How do prostaglandins contribute to the protection of the stomach?

Answer 25

Answer: Prostaglandins increase mucosal thickness and stimulate bicarbonate production, enhancing the protective mechanisms of the stomach.

Question 26

Question: What characterizes the cephalic phase of gastric secretion, and what stimuli trigger it?

Answer 26

Answer: The cephalic phase involves increased secretion and is triggered by the sight, smell, taste, or thought of food, as well as a decrease in blood glucose.

Question 27

Question: What characterizes the gastric phase of gastric secretion, and what is the primary stimulus for this phase?

Answer 27

Answer: The gastric phase is marked by increased secretion and is primarily stimulated by stomach distension resulting from the presence of food.

Question 28

Question: What characterizes the intestinal phase of gastric secretion, and what are the stimuli that trigger it?

Answer 28

Answer: The intestinal phase involves decreased secretion and is triggered by digested proteins/fat in the duodenum. The presence of fat or low pH in the duodenum inhibits gastric secretion.

Question 29

Question: What initiates the cephalic phase of gastric secretion at the neural level, and what is its impact on the stomach?

Answer 29

Answer: Nerve impulses to the medulla oblongata cause parasympathetic neurons via the vagus nerves to increase HCl and pepsin secretion in the stomach during the cephalic phase.

Question 30

Question: Besides neural impulses, what hormonal factor plays a role in the cephalic phase of gastric secretion, and where is it secreted?

Answer 30

Answer: Gastrin secretion is promoted in the antrum of the stomach during the cephalic phase, and this hormone stimulates further HCl and pepsin secretion.

Question 31

Question: What physiological event triggers the gastric phase of increased gastric secretion, and what is the subsequent response in terms of HCl, pepsin, and gastrin?

Answer 31

Answer: Stomach distension triggers a parasympathetic reflex during the gastric phase, leading to further secretion of HCl, pepsin, and gastrin.

Question 32

Question: What triggers the inhibition of gastric secretion during the intestinal phase, and what are the primary mechanisms through which this inhibition occurs?

Answer 32

Answer: Chyme entering the duodenum, containing fat or enough HCl to lower the pH to below 2, triggers the inhibition of gastric secretion during the intestinal phase. This inhibition occurs through three main routes: (i) Neuronal impulses are sent to the medulla to decrease parasympathetic stimulation of gastric glands. (ii) Local reflexes in the gut wall lead to decreased secretion. (iii) The release of three local hormones (secretin, gastric inhibitory peptide, and cholecystokinin) travel via the bloodstream to the gastric glands and inhibit secretion.

Question 33

Question: What event triggers the inhibition of gastric secretion during the intestinal phase?

Answer 33

Answer: Chyme entering the duodenum, containing fat or enough HCl to lower the pH to below 2, triggers the inhibition of gastric secretion during the intestinal phase.

Question 34

Question: What are the three main routes through which inhibition of gastric secretion occurs during the intestinal phase?

Answer 34

Neuronal impulses are sent to the medulla to decrease parasympathetic stimulation of gastric glands.

Local reflexes in the gut wall lead to decreased secretion.

The release of three local hormones (secretin, gastric inhibitory peptide, and cholecystokinin) travels via the bloodstream to the gastric glands and inhibits secretion.

Question 35

Question: What triggers the neuronal inhibition of HCl secretion, and which reflex is involved?

Answer 35

Answer: Partially digested protein and the presence of fat in the duodenum, combined with a lower pH from gastric acid, triggers the neuronal inhibition of HCl secretion by the “enterogastric reflex.” This reflex is mediated by the medulla oblongata and leads to a decrease in parasympathetic stimulation.

Question 36

Question: What hormones contribute to the hormonal inhibition of HCl secretion, and from where are they released?

Answer 36

Answer: Hormones contributing to hormonal inhibition include secretin and cholecystokinin released from the duodenum. Other inhibitors include GIP (gastric inhibitory peptide), gastrone, glucagon, and VIP (vasoactive intestinal peptide). Additionally, somatostatin, a paracrine agent, is released in response to increased [HCl].

Question 37

Question: Define diarrhea.

Answer 37

Answer: Diarrhea is the passing of watery stools more than three times a day.

Question 38

Question: Differentiate between acute and chronic diarrhea in terms of onset and duration.

Answer 38

Answer: Acute diarrhea comes on suddenly and lasts for five to 10 days, while chronic diarrhea persists for more than two weeks.