GI Physiology 1 Flashcards
What are the main functions of the stomach?
Temporary storage of food input
Mechanical digestion (breaking food into smaller particles)
Chemical digestion (breakdown of proteins)
Regulation of chyme output into the duodenum
Secretion of intrinsic factor for vitamin B12 absorption
Name the anatomical parts of the stomach.
Gastro-Oesophageal Sphincter
Cardia
Fundus
Greater Curvature
Lesser Curvature
Body (Corpus)
Pylorus (and pyloric sphincter)
What is the function of mucous cells in the stomach?
Secrete alkaline mucin to protect the stomach lining from acid
What is the function of parietal cells?
Produce hydrochloric acid (HCl)
What is the function of chief cells?
Produce pepsinogen, which is converted into pepsin to break down proteins
What do G cells secrete and what is their function?
Secrete gastrin, which stimulates acid production
How much hydrochloric acid (HCl) is secreted daily by the stomach?
2 liters per day
What is the alkaline tide?
The release of bicarbonate (HCO3-) into the blood following acid production
What is the role of intrinsic factor in the stomach?
It binds to vitamin B12 for absorption in the terminal ileum
What regulates gastric emptying?
Volume in the stomach, chyme pH, and duodenal feedback mechanisms
What are the three phases of gastric secretion?
Cephalic phase
Gastric phase
Intestinal phase
What triggers the cephalic phase of gastric secretion?
Sight, smell, taste, or thought of food
What stimulates gastric secretion during the cephalic phase?
Vagal stimulation and gastrin release
What happens during the gastric phase?
Food distends the stomach, stimulating acid and enzyme secretion
What inhibits gastrin release during the gastric phase?
Low stomach pH
What triggers the intestinal phase?
Chyme entering the duodenum
Which hormones inhibit gastric secretions during the intestinal phase?
Secretin, Gastric Inhibitory Peptide (GIP), and Cholecystokinin (CCK)
What effect does fatty chyme have on gastric emptying?
It slows gastric emptying to allow digestion and absorption
What are the three sections of the small intestine?
Duodenum
Jejunum
Ileum
What is the primary function of the small intestine?
Digestion and absorption of nutrients
What feature increases the surface area of the small intestine?
Villi and microvilli (brush border)
What enzymes aid digestion in the small intestine?
Enzymes from the pancreas, bile, and intestinal wall amylase (carbohydrate digestion), lipase (fat digestion), and proteases such as trypsin and chymotrypsin (protein digestion).
How is carbohydrate absorbed in the small intestine?
Broken down into monosaccharides and absorbed via co-transport with sodium
How is fat absorbed in the small intestine?
Emulsified by bile salts, broken down into micelles, and absorbed passively
What is the function of lacteals in the villi?
They absorb dietary fats into the lymphatic system
What role does sodium play in nutrient absorption?
It helps co-transport glucose and amino acids across the intestinal lining via sodium-dependent active transport
What are the exocrine functions of the pancreas?
Secretion of digestive enzymes such as amylase (carbohydrate digestion), lipase (fat digestion), and proteases (protein digestion), as well as bicarbonate to neutralize stomach acid.
Which hormone stimulates pancreatic secretion?
Secretin
Name the enzymes secreted by the pancreas.
Amylase (breaks down carbohydrates into maltose)
Lipase (breaks down fats into glycerol and free fatty acids)
Ribonuclease (breaks down RNA into nucleotides)
Deoxyribonuclease (breaks down DNA into nucleotides)
Proteases (e.g., trypsin, which breaks down proteins into peptides)
What is the role of bicarbonate in pancreatic secretions?
Neutralizes acidic chyme entering the duodenum
What are the main functions of the liver?
Protein synthesis (e.g., clotting factors)
Metabolism of carbohydrates, proteins, and fats
Detoxification of ammonia, hormones, and drugs
Storage of glycogen and vitamins
What structures make up the hepatic triad?
Hepatic portal vein, hepatic artery, bile duct
What is the role of bile?
Aids in fat digestion and absorption
Where is bile stored?
Gallbladder
What stimulates bile release?
Cholecystokinin (CCK) and vagal stimulation
What is bilirubin?
A breakdown product of hemoglobin
Where is bilirubin processed?
Liver
How is bilirubin excreted?
In bile via the intestines
What condition can arise from excess bilirubin?
Jaundice
What are the two forms of bilirubin?
Unconjugated (indirect) and conjugated (direct)
