Week 16 / GI system 2 Flashcards
Q: What shape is the stomach, and what is its most notable feature?
A: The stomach is a J-shaped sac-like chamber and is the most distensible part of the gastrointestinal tract.
Q: What are the main functions of the stomach?
[6]
Stores ingested food
Secretes gastric juice (acid, mucus, intrinsic factor, digestive enzymes)
Mixes food with gastric juice
Initiates digestion of proteins and fats
Kills bacteria
Moves food (chyme) at a controlled and steady rate into the duodenum.
Q: What components make up the gastric juice secreted by the stomach? [4]
A: Gastric juice consists of:
Hydrochloric acid (HCl)
Mucus
Intrinsic factor
Digestive enzymes (e.g., pepsin and lipase)
Q: What role does gastric juice play in digestion? [3]
Initiate digestion of proteins and fats
Kill bacteria through the acidic environment created by HCl
Facilitate enzyme activity, especially pepsin, in protein breakdown.
Q: How does the stomach move food (chyme) into the duodenum?
the pyloric sphincter.
Q: What is the function of the fundus in the stomach?
A: The fundus is the upper part of the stomach, which stores food and gas. It is involved in gastric juice secretion and serves as a reservoir for food before it moves to the body.
Q: What is the role of the esophagus?
A: The esophagus carries food from the mouth to the stomach
What is the role of the lower esophageal sphincter in relation to the stomach?
the lower esophageal sphincter (LES) controls the opening between the esophagus and the stomach to prevent stomach contents from refluxing back into the esophagus.
Q: What does the body of the stomach secrete? [3]
Mucus (protective lining)
Pepsinogen (inactive enzyme precursor)
Hydrochloric acid (HCl) (for digestion and sterilization)
Q: What is the role of the duodenum in the stomach’s function?
A: The duodenum is the first part of the small intestine, and it receives chyme from the stomach through the pyloric sphincter. It is the site where further digestion of nutrients occurs and bile from the liver and enzymes from the pancreas are added.
Q: What is the function of the pyloric sphincter?
A: The pyloric sphincter regulates the passage of chyme from the stomach into the duodenum, controlling the rate at which food moves from the stomach to the small intestine.
Q: What does the antrum of the stomach secrete? [3]
Mucus (for protection)
Pepsinogen (to aid in protein digestion)
Gastrin (a hormone that stimulates gastric acid secretion and motility)
What are gastric folds?
What is the function of gastric mucosal folds in the stomach?
A: Gastric mucosal folds are the folds in the stomach lining.
allow the stomach to expand when filled with food. They also help to increase the surface area for digestion and absorption.
What are gastric pits?
what is their role?
A: Gastric pits are small depressions in the stomach lining that lead to the gastric glands
They house specialized cells that secrete gastric juices, such as mucus, hydrochloric acid (HCl), and digestive enzymes.
Q: What do mucous cells in the gastric mucosa secrete?
Whats the function of whats secreted ?
Mucous cells secrete mucus,
which forms a protective barrier that shields the stomach lining from the corrosive effects of gastric acid and digestive enzymes.
Q: What are the components of gastric glands and what do they secrete?
A: Gastric glands are located at the base of gastric pits and contain several types of cells:
Parietal cells – Secrete hydrochloric acid (HCl) and intrinsic factor
Chief cells – Secrete pepsinogen (the inactive form of the enzyme pepsin)
Mucous cells – Secrete mucus to protect the stomach lining.
Q: What is the role of parietal cells in the stomach?
A: Parietal cells secrete hydrochloric acid (HCl), which aids in food digestion by lowering the stomach pH, and intrinsic factor, which is necessary for vitamin B12 absorption in the small intestine.
Q: What do chief cells secrete in the stomach?
A: Chief cells secrete pepsinogen, the inactive form of the enzyme pepsin. Pepsinogen is activated by HCl into pepsin, which then begins protein digestion in the stomach.
Q: What is the function of the submucosa in the stomach?
A: The submucosa is a layer of connective tissue that supports the mucosa. It contains blood vessels, lymphatics, and nerve fibers, and helps provide nutrients to the stomach lining and regulates digestive functions.
Q: What is the source of hydrochloric acid (HCl) in the stomach and its function?
A: Hydrochloric acid (HCl) is secreted by parietal cells in the stomach. Its function is to sterilize the ingested meal by killing pathogens and assist in the hydrolysis of food, especially proteins.
Q: What is the source of intrinsic factor in the stomach ?
What is the function?
A: Intrinsic factor is secreted by parietal cells.
Its function is to aid in the absorption of vitamin B12 in the small intestine.
What is the source of pepsinogen in the stomach?
What is the function?
A: Pepsinogen is secreted by chief cells in the stomach.
It is an inactive precursor to pepsin, an enzyme that digests proteins once activated by acidic conditions in the stomach.
Q: What is the source of mucus and bicarbonate in the stomach?
What is the function?
A: Surface mucous cells secrete mucus and bicarbonate.
These products form a protective layer on the stomach lining, providing gastroprotection from the corrosive effects of gastric acid and digestive enzymes.
What are trefoil factors secreted by?
what is their function in the stomach?
Trefoil factors are secreted by surface mucous cells
play a role in gastroprotection, particularly in mucosal healing and repair.
What is the source of histamine in the stomach ?
what is its function?
A: Histamine is secreted by enterchromaffin-like (ECL) cells.
It stimulates gastric acid secretion by binding to H2 receptors on parietal cells.
What is the source of gastrin in the stomach?
what is its function?
A: Gastrin is secreted by G cells in the stomach.
Its function is to stimulate gastric acid secretion by parietal cells and increase gastric motility.
What is the source of gastrin-releasing peptide (GRP) ?
what is its function?
A: GRP is secreted by nerves
stimulates the release of gastrin from G cells, which in turn increases gastric acid secretion.
Q: What is the source of acetylcholine (ACh) ?
what is its function?
A: Acetylcholine (ACh) is secreted by nerves
stimulates both gastric acid secretion from parietal cells and the release of pepsinogen from chief cells.
Q: What is the source of somatostatin and its function in the stomach?
A: Somatostatin is secreted by D cells in the stomach. It functions to inhibit gastric acid secretion and gastrin release, thus regulating gastric function.
Q: What triggers the cephalic phase of gastric secretion and what occurs during this phase?
A: The cephalic phase is triggered by the thought, smell, sight, or taste of food. This phase prepares the stomach for food intake by increasing gastric secretion (acid, enzymes) and gastric motility, even before food enters the stomach.
Q: What triggers the gastric phase of gastric secretion and what occurs during this phase?
A: The gastric phase is triggered by the presence of food in the stomach. This phase involves the secretion of gastric acid, pepsinogen, and other digestive enzymes to aid in digestion and the mixing of food with gastric juices.
Q: What triggers the intestinal phase of gastric secretion and what happens during this phase?
A: The intestinal phase is triggered by the movement of food from the stomach into the duodenum. This phase serves to slow gastric secretion and motility to allow for optimal digestion and absorption in the small intestine.
Q: How is carbohydrate digestion carried out in the stomach, and what affects it?
A: Carbohydrate digestion continues with salivary amylase in the stomach but is partially inhibited by the acidity of gastric juices, which slows down the breakdown of starches.
Q: What role does pepsin play in digestion in the stomach?
A: Pepsin begins the partial digestion of proteins in the antrum of the stomach, breaking down proteins into smaller peptides.
Q: Which substances are absorbed in the stomach?
A: The stomach primarily absorbs alcohol and aspirin, while most other nutrients are not absorbed here.
Q: How does the gastric mucosal barrier protect the stomach from damage by HCl?
A: The gastric mucosal barrier protects the stomach by making cell membranes of mucosal cells impermeable to HCl, and by forming tight junctions between adjacent cells that prevent acid penetration.
Q: What is the role of mucus in protecting the stomach lining?
A: The HCO₃⁻-rich mucus acts as a physical barrier to protect the stomach lining and as a chemical barrier, neutralizing acid near the mucosa.
Q: How does the stomach repair its lining?
A: The stomach lining is replaced every 3 days due to the rapid rate of cell division in the gastric mucosa.
Q: How do prostaglandins help protect the stomach?
A: Prostaglandins help protect the stomach by inhibiting acid secretion and promoting the secretion of alkaline mucus, which further helps neutralize stomach acid.
Q: What are the main digestive and absorptive functions of the small intestine?
A: The small intestine is the main site for digestion and absorption of ingested food, secretes aqueous salt and mucus for lubrication and protection, and uses segmentation and peristaltic contractions to mix, propel chyme, and facilitate absorption.
Q: How does digestion occur in the small intestine?
A: Digestion in the small intestine occurs through the action of bile, pancreatic enzymes, and intestinal (brush-border) enzymes.
Q: Where does absorption occur in the small intestine?
A: Absorption occurs along the entire length of the small intestine but is largely concentrated in the duodenum and jejunum.
Q: How does the structure of the small intestine maximize surface area for absorption?
A: The mucosal surface is thrown into permanent circular folds, which increase the surface area by 3-fold. Villi (microscopic finger-like projections) project from the folds, increasing the surface area by 10-fold. Each villus is covered by epithelial cells with microvilli (brush border), which further increase surface area by 20-fold.
Q: What types of digestive enzymes are expressed on the membranes of microvilli in the small intestine?
A: The brush border of microvilli expresses three types of digestive enzymes:
Enteropeptidase
Disaccharidases
Aminopeptidases
